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. 2021 Oct 6;6(41):26857–26869. doi: 10.1021/acsomega.1c02738

Use of Piers–Rubinsztajn Chemistry to Access Unique and Challenging Silicon Phthalocyanines

Anjuli M Szawiola †, Benoit H Lessard ‡, Hasan Raboui §, Timothy P Bender †,§,∥,*
PMCID: PMC8529611  PMID: 34693107

Abstract

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Axial functionalization is one mode that enables the solubility of silicon phthalocyanines (SiPcs). Our group observed that the use of typical axial functionalization methodologies on reaction of Cl2SiPc with the chlorotriphenyl silane reagent unexpectedly resulted in the equal formation of triphenyl silyloxy silicon tetrabenzotriazacorrole ((3PS)-SiTbc) and the desired bis(tri-phenyl siloxy)-silicon phthalocyanine ((3PS)2-SiPc). The formation of a (3PS)-SiTbc was unexpected, and the separation of (3PS)-SiTbc and (3PS)2-SiPc was difficult. Therefore, in this study, we investigated the use of Piers–Rubinsztajn (PR) chemistry as an alternative method to functionalize the axial position of a SiPc to avoid the generation of a Tbc derivative. PR chemistry is a novel method to form a Si–O bond starting with a Si–H-based reactant and a −OH-based nucleophile enabled by tris(pentafluorophenyl)borane as a catalyst. The PR chemistry was screened on several fronts on how it can be applied to SiPcs. It was found that the process needs to be run in nitrobenzene at a molar ratio and at a particular temperature. To this end, the triphenylsiloxy derivative (3PS)2-SiPc was produced and fully characterized, without the production of a Tbc derivative. In addition, we explored and outlined that the PR chemistry method can enable the formation of other SiPc derivatives that are inaccessible utilizing other established axial substitution chemistry methods such as (TM3)2-SiPc and (MDM)2-SiPc. These additional materials were also physically characterized. The main conclusion is that the PR chemistry method can be applied to SiPcs and yield several alternative derivatives and has the potential to apply to additional macrocyclic compounds for unique derivative formation.

Introduction

Phthalocyanines (Pcs) are a class of materials consisting of four (4) imine-linked isoindole subunits that are used as stable dyes and pigments due to their high absorption coefficient. They form coordination complexes with almost every single metal in the periodic table. Their 18 π-electron, macrocyclic, planar structure provides an interesting variety of physical, electrochemical, and optoelectronic properties, including their ability to absorb visible light.1

Silicon phthalocyanines (Figure 1, SiPcs) have a good history within the dye and pigment space but have recently emerged to be of general interest for organic electronic applications due to their optoelectronic properties and the relative abundance of silicon. SiPcs have been applied in a variety of organic electronic devices, including organic light-emitting diodes,2,3 organic thin-film transistors,4,5 planar heterojunction organic photovoltaics,6,7 bulk heterojunction organic photovoltaics as both electron acceptors/conductors and ternary additives,3,8−17 and dye-sensitized solar cells.18−20

Figure 1.

Figure 1

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Generic structures of a silicon Pc (SiPc) with axial functionalization (X). (a) Process to make an axial functionalized SiPc: (i) reaction of SiCl4 with 1,3-diiminoisoindoline (1,3-DII) in quinoline as a solvent for approximately 4 h at a refluxing temperature of 219 °C under an inert N2 (g) atmosphere; (ii) then, on the formation of Cl2-SiPc, axial functionalization can occur (axial substituents shown as X) on reaction with a chloro trialkyl/aryl silane in the presence of sodium hydroxide and Aliquat phase catalysis at a refluxing temperature of 132 °C in chlorobenzene for 2–3 h and is called the “AQ” method; (iii) an alternative pathway is to hydrolyze the Cl2-SiPc to (HO)2-SiPc and (iv) react (HO)2-SiPc also with chloro trialkyl/aryl silanes at a refluxing temperature of 115 °C in pyridine for ∼5 h and is called the “BG” method; (v) to specifically form a silicon tetrabenzotriazacorrole (SiTbc; unique C=C highlighted in pink), (HO)2-SiPc is reacted with a chloro trialkyl/aryl silane at 100 °C in pyridine in the presence of magnesium (Mg). (b) 3D crystal molecular structures of (3PS)2-SiPc (top, CCDC deposition number:1824908; database identifier GICYAV) and 3PS-SiTbc (bottom, CCDC deposition number: 1817928; database identifier KICMIV; unique C=C bond highlighted in pink), where 3PS is triphenyl siloxane. Carbon—gray; nitrogen—blue; silicon—yellow; oxygen—red. On the formation of Cl2-SiPc, axial substitution can proceed with a mixture of reagents of chloro trialkyl/aryl silane, sodium hydroxide, potassium carbonate, and an Aliquat phase-transfer catalyst for refluxing in chlorobenzene (Figure 1, point ii) and presumably forms (HO)2-SiPc in situ due to the use of sodium hydroxide and an Aliquat,23 and (HO)2-SiPc reacts with the chloro trialkyl/aryl silane.

Axial functionalization is one manner of modifying a subset of phthalocyanines (Pcs) with coordinated metallic atoms having additional atomic bonding options. The bonding options can enable a Pc to transition from a pigment status to the dye status and can enable significant variations. Specifically, for organic electronics applications, SiPcs require variations of axial functionalization to enable different morphological, nanostructurural, and physical properties including solubility,21,22 while leaving their desired optoelectronic properties intact. For example, (HO)2-SiPcs and Cl2-SiPcs have been modified by the use of various chlorosilane derivatives21,23 and react with alcohols at reflux to make alternative axial substituents non-silicon-based.24,25 Each approach valid to access a variety of SiPc products yet is a limitation when it comes to axial substituents for the SiPcs. This approach and requirements are also analogous to what has also been employed within boron subphthalocyanine (BsubPc) derivatives to also enable varying physical and nanostructural properties.26

The general mechanism for the formation of a Pc is the reaction of a phthalonitrile precursor (which can have peripheral substituents) with the associated metallic source in a halogenated form to enable the metallic source to be a Lewis acid. The relative Lewis acidity of the metallic source to the Lewis basicity of the phthalonitrile enables the formation of the Pc. Short of the Lewis basicity and acidity being a factor, the actual mechanism of the formation of a Pc is not established to date. SiCl4 has low Lewis acidity; therefore, to form a SiPc, the standard need is to react 1,3-diiminoisoindoline (1,3-DII) with SiCl4 at high temperature (Figure 1, point i). 1,3-DII is an alternative to and a derivative of phthalonitrile needed when the metallic source of a Pc has a low Lewis acid (such as SiCl4). 1,3-DII is derived from a phthalonitrile on reaction to NaOCH3 on reflux in methanol and bubbling ammonia (NH3) through the reactor.27 1,3-DII ultimately has a higher Lewis basicity due to its nitrogen atomic features and therefore enables the formation of Cl2-SiPc on reaction with SiCl4. Cl2-SiPc has low solubility and is a pigment, and its crystal structure has been established.7,28,29

One more specific method used for axial functionalization of SiPcs involves first the formation of (HO)2-SiPc on hydration of Cl2-SiPc (Figure 1, point iii). The reaction of chloro-tri(alkyl/aryl) silane with (HO)2-SiPc in pyridine at reflux under an inert atmosphere then enables the axial substituent and the associated physical properties to vary (Figure 1, point iv).21,23 This method is (relatively) limited by the availability of chloro-tri(alkyl/aryl) silane derivatives and is relatively simple chemistry with a HCl/pyridine-HCl byproduct.

The stimulation of this report resulted from our attempt to synthesize bis(tri-phenyl siloxy)-silicon phthalocyanine (3PS)2-SiPc using this methodology, the reaction of (HO)2-SiPc with an excess of chloro-triphenylsilane in refluxing pyridine (Figure 1, point iv). The unexpected results we observed were a mixture of both the desired product (3PS)2-SiPc and an unexpected side product. Each product was isolated by train sublimation.30 We observed that the product remaining in the boat (∼50%) had a different appearance from the material that sublimed and traveled down the tube (∼50%). We characterized both the product in the boat and the product that sublimed first by UV–vis absorption spectroscopy (Figure 2a, a direct point of comparison, (3HS)2-SiPc10 is included). The product that was sublimed has two characteristic peaks which are similar to those of (3HS)2-SiPc (636 and 675 nm), while the product that was left in the boat contains a similar absorption profile and has an additional absorption at 443 nm (Figure 2b). This new peak is consistent and characteristic of a ring contraction of the SiPc macrocycle, as has been reported by Zhang et al.,31,32 Kobayashi et al.,33,34 and Raboui et al.,35,36 forming a compound known as a tetrabenzotriazacorrole (Tbc, Figure 1), a ring-contracted Pc analogue; in this case, (tri-phenyl)silicon tetrabenzotriazacorrole (3PS-SiTbc, Figure 2). These observations of the formation of 3PS-SiTbc were not noted in the two previous reports of the synthesis of (3PS)2-SiPc.23,37 In the previous work and report of Raboui et al.,35,36 it was clear that a unique set of reagents, solvents, and temperatures is needed to firmly form a SiTbc derivative from (HO)2-SiPc: magnesium (Mg) and hydrochloride acid (HCl) in pyridine at reflux, with Mg being a requirement for complete conversion (Figure 1, point v). As Mg has a major impact, maybe it is not fully required for the formation of a SiTbc. Rather, as this reaction was held, it would generate HCl on reaction of (HO)2-SiPc with chloro-triphenylsilane (Figure 2), and therefore, the potential presence of pyridine-HCl during the reaction is a factor into the formation of SiTbcs.

Figure 2.

Figure 2

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(a) Reaction scheme for the formation of (3PS)2-SiPc and 3PS-SiTbc. (b) UV–vis absorption spectroscopy in toluene solution of (3PS)2-SiPc (isolated on sublimation), 3PS-SiTbc (left in the sublimation boat), and (3HS)2-SiPc (for reference).

We then considered how we might synthesize (3PS)2-SiPc without the significant formation of a Tbc. Piers–Rubinsztajn (PR) chemistry38 is one method to be considered. We have previously demonstrated the use of PR chemistry in coupling triarylamines to siloxane oligomers or polymers for the generation of new materials.39−44 This type of chemistry has also been used to make many other functional materials such as siloxane-based foams,45,46 surfactants,47 cross-linkers with lignin,48 elastomers,45,49 polymers,50−60 dendrons,57,61 and other unique cyclic macrocycles.62 The PR reaction uses tris(pentafluorophenyl)borane as an organic Lewis acid catalyst, coupling a Si–H bond to an oxygen-based nucleophile and then forming a Si–O bond.63−65 Examples of oxygen-based nucleophiles include hydroxy (−OH) and ether (−OR) groups and yield hydrogen (H2) or methane (CH4) as a byproduct.

To expand the scope of this reaction, it was hypothesized that the PR reaction could be used to (1) eliminate the formation of a Tbc when synthesizing the triphenyl derivatized SiPc and additionally (2) access unique, non-chlorosilane derivatives (i.e., siloxane oligomeric derivatives). The goal of this study was to do determine the feasibility of using the PR reaction specifically with the starting material (HO)2-SiPc yielding silyloxo-SiPcs, a broad class of SiPcs with high solubility that enables several unique applications as outlined above and can enable unique derivatives that are relevant to the field. We do also compare two other methods, the “BG” and “AQ” methods (outlined below), as for these, they will generate pyridine–HCl during reaction.

Results and Discussion

Reaction Scoping

As outlined above, the intention of this work had two goals: (1) to establish the PR reaction to functionalize SiPcs, without the generation of the Tbc side product and (2) to access unique SiPc derivatives. To start, the PR reaction was scoped to assess its potential for functionalizing SiPcs. To enable relative easy scoping/assessment, we used a molecular fragment known to give outstanding solubility: tri-n-hexylsilane (3HS), a derivative that would yield bis(tri-n-hexylsilyl oxide)silicon phthalocyanine, (3HS)2-SiPc.9,10,14,16,66,67 In this case, the Si–H bond was in tri-n-hexylsilane, the nucleophile was the hydroxyl group attached to the (HO)2-SiPc, and the volatile gas released was hydrogen (H2) gas (caution).

The impact of a variety of solvents, the number of catalyst doses, and temperature on reaction progress was investigated and is outlined in Table 1. The different solvents chosen for this reaction were to scope common organic solvents that were inert to this reaction. The number of catalyst doses (i.e., one or two) was also investigated to ensure the presence of a sufficient amount of catalyst during the reaction. Since previous work demonstrated the ability of triarylamines to be functionalized by the PR reaction at 25 °C,44 this temperature was selected to be studied for SiPc functionalization as well. The reaction rate at a higher temperature of 100 °C was also studied to assess temperature dependence on the PR reaction process.

Table 1. Scoping Conditions Explored for the PR Reactiona.

solvent calculated Hammett parameter68 catalyst dose 1 catalyst dose 2 temperature (°C) reaction resultb
toluene –0.170 5 mol %   100 (−)
        25 (−)
      5 mol % 100 (o)
        25 (−)
1,2-dichlorobenzene 0.454 5 mol %   100 (−)
        25 (−)
      5 mol % 100 (o)
        25 (−)
chlorobenzene 0.227 5 mol %   100 (−)
        25 (−)
      5 mol % 100 (−)
        25 (−)
nitrobenzene 0.778 5 mol %   100 (−)
        25 (−)
      5 mol % 100 (+)
        25 (−)
dichloromethane   5 mol %   100 (−)
      5 mol % 25 (−)
xylenes –0.247 5 mol %   100 (−)
        25 (−)
      5 mol % 100 (−)
        25 (−)
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a

(−)—No axial substituted bis(tri-n-hexylsilyl oxide)silicon phthalocyanine, (3HS)2-SiPc, formed; (o)—modest axial substituted (3HS)2-SiPc formed; (+)—full functionalization axial substitute (3HS)2-SiPc achieved.

b

(o) denotes a partially positive result.

Thin-layer chromatography (TLC) analysis was used to monitor the reaction progress with a solvent system of 1:1 hexanes/tetrahydrofuran (THF). The starting material, (HO)2-SiPc, has poor solubility in the TLC solvent system and adheres to the base of the TLC system, while the functionalized SiPc, (3HS)2-SiPc, is very soluble and has high TLC mobility, and the intermediate (3HS)-Cl-SiPc has modest solubility and mobility on a TLC. The reaction progress can be visualized by the intensity under visible light, relevant to the starting material spot at the baseline. On exploration of a significant matrix (Table 1), it was discovered that the conditions that led to complete conversion of the starting material were as follows: nitrobenzene, with two 5 mol % catalytic doses and a temperature of 100 °C over 6 h time. This result gave positive confirmation that the PR reaction can indeed be used to functionalize SiPcs.

In retrospect, it is not surprising that nitrobenzene is the best solvent based on a Hammett parameter assessment (Table 1). The Hammett parameter values can be summarized from a review by Hansch.68 Nitrobenzene has the highest positive Hammett parameter, indicating its π-acidity relative to the other aromatic solvents. Past results focusing on triarylamine44 and polysiloxane derivatization44 worked well in toluene and xylenes, respectively. However, the π-acidity of toluene and xylene relative to nitrobenzene is clearly a factor here whereby the molecular level interactions between nitrobenzene and tris(pentafluorophenyl)borane would be far less favorable (two π-acidic/Lewis-acidic materials). These results likely then set a parameter for less reactive nucleophilic species in the PR process to use a π-acidic solvent. The presumed low nucleophilicity of (HO)2-SiPc is likely attributable to the steric effect of its molecular size and positioning of the −OH group. In this process, nitrobenzene is also able to effectively solubilize all three reagents, thereby making it the solvent of choice moving forward.

Synthesis of (3PS)2-SiPc via the PR Methodology

After having confirmed PR chemistry as a viable means to functionalize SiPcs, one of the initial goals of using PR chemistry with SiPcs (as stated above) is to eliminate the formation of Tbcs while working to obtain certain derivatives. The PR methodology outlined above was then applied to generate the desired bis(tri-phenyl siloxy)-silicon phthalocyanine ((3PS)2-SiPc). This methodology worked and did not generate the undesired Tbc derivative, as confirmed by UV–vis absorption spectroscopy (Figure 3) and other characterization techniques [nuclear magnetic resonance (NMR), Figures S1, S8.5; mass spectrometry, Figure S2, S8.10]. This is therefore the first confirmation of the uniqueness of the PR methodology, which can be applied to Pcs and target unique and desirable derivatives.

Figure 3.

Figure 3

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UV–vis (dashed) and PL spectra (solid) of (3PS)2SiPc in DCM. PL excitation wavelength indicated in the top left and colored in the plot. The PL spectrum was generated on photoexcitation at 350, 610, 650, and 670 nm—peak absorption points.

The absorption spectrum of (3PS)2-SiPc has a strong Q-band transition at 676 nm and a Soret band transition at ∼350 nm, typical and characteristic of Pcs. Interestingly, the Q-band transition is red-shifted 8 nm as compared to a literature value for this compound obtained in toluene (668 nm23), demonstrating a potential solvatochromic effect. Figure 3 also shows the photoluminescence (PL) spectra of this compound at different excitation wavelengths. The PL excitation wavelengths were selected as the absorbance peaks in the UV–vis absorbance spectrum (350, 610, 650, and 670 nm). The material retains the same PL profile and thus the structure, regardless of the excitation wavelength. In addition, a Stokes shift of ∼10 nm can be observed. The Stokes shift, as obtained from literature values, in toluene is 4 nm.23 The larger Stokes shift observed in dichloromethane (DCM) again indicates the stabilizing nature of DCM on the excited state of this compound, such that its maximum emission wavelength is 6 nm red-shifted as compared to that in toluene.

To study the material morphology in detail, a thermal analysis [thermal gravimetric analysis/differential scanning calorimetry (TGA/DSC), Figures S3 and S4] was conducted. Based on the thermal analysis, (3PS)2-SiPc has a higher Tc and Tm than those observed with an alkyl derivative, for example, the bis(tri-butyl siloxy) SiPc derivative, (3BS)2SiPc.16 This would indicate a higher degree of structure and order to the solid state. This is confirmed by higher enthalpy of crystallization and melting values. (3PS)2-SiPc also has a higher 5% weight loss temperature than the 3BS derivatives, indicating a higher thermal stability.

As SiPcs are relevant to organic electronic applications, electrochemistry was also explored. Half-wave potentials, Ered and Eox, for (3PS)2-SiPc were also obtained via cyclic voltammetry (CV, Table 2, Figure S5) and were found to be typical of SiPc derivatives10,20 and are also consistent with the previously reported values for (3PS)2-SiPc, within 15 mV for both the oxidation and reduction potentials.

Table 2. Characterization Results of the Compound (3PS)2-SiPc.

characteristic (3PS)2SiPc via PR chemistry (3PS)2SiPc literature values
Ered,1 (half-wave) –0.82 V versus Ag/AgCl –0.88 (versus SCE)37
    –0.835 V (versus Ag/AgCl)a
Eox,1 (half-wave) 1.01 V versus Ag/AgCl 0.95 V (versus SCE)37or 0.995 V (versus Ag/AgCl)a
Td,5% 395 °C  
Tg/Tc./Tm -/274 °C/382 °C  
ΔHc./ΔHm 59.7 J/g/67.2 J/g  
λmax, abs., solution 676 nm (DCM) 668 nm (toluene)23
λmax, PL., solution 686 nm (DCM) 672 nm (toluene)23
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a

Converted to Ag/AgCl by adding 0.045 V versus SCE values.

Other Derivatives via the PR Methodology

We then explored the PR methodology to enable the use of unique commercially available siloxane oligomers with silane-derivative points, which are unavailable as chlorosilanes analogues to yield unique SiPc derivatives with siloxane oligomers in the axial position. The examples we considered were bis(tris(trimethylsiloxy) silyl oxide) silicon phthalocyanine, (TM3)2-SiPc, and bis(bis(trimethylsiloxy)methyl silyl oxide) silicon phthalocyanine, (MDM)2-SiPc (outlined in Scheme 1). With regard to the generation of (TM3)2-SiPc, using the PR method outlined above, upon MS characterization, it was found that there was a mixture of compounds, including a minor amount of a Tbc derivative, resulting from the (TM3)2-SiPc sample (Figure S6). The product mixture resulting from the MS analysis also contained a variety of different axially functionalized siloxane derivatives. It would appear that a significant amount of metathesis occurred among the TM3 molecular fragment on MS characterization. It should be noted, however, that a UV–vis spectrum of the mixture of compounds did not indicate Tbc formation by the lack of the characteristic peak of a Tbc at ∼440 nm (Figure 4). This therefore indicates the possibility of Tbc formation only during the MS technique. Therefore, this is to note that the formation of Tbcs may occur via varying ways of analysis and under varying analytical conditions. However, NMR analysis (Figure S7) also firmly indicated the lack of Tbc formation during the synthetic process. Three separate Pc-species peaks were observed, and more −O–Si–C–H protons (∼84 H) than would be expected of a tris(trimethylsiloxy)silane on a difunctional SiPc (54 H) were observed, thus confirming a mixture of products. Due to the structural similarities, it is difficult to distinguish which derivatives are present. Thus, PR chemistry does not yield a pure compound using TM3 and is clearly TM3-related. Additional characterization of the (TM3)2-SiPc mixture was done as the basic physical properties of a SiPc are dependent on the Pc core and the bond to Si and not the variations in the axial siloxane (Table 3; CV, TGA/DSC, PL, and UV–vis absorbance). (TM3)2-SiPc, with variations in the siloxane axial moiety, still has a relative thermal stability of Td,5% of 264 °C. This gives this derivative worthiness of application.

Scheme 1. Generic PR Reaction Conditions Applied to SiPcs to Yield Different Derivatives.

Scheme 1

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Bis(tri-n-hexylsilyl oxide)silicon phthalocyanine = (3HS)2-SiPc bis(tri-phenyl siloxy)-silicon phthalocyanine = (3PS)2-SiPc; bis(tris(trimethylsiloxy) silyl oxide) silicon phthalocyanine = (TM3)2-SiPc and bis(bis(trimethylsiloxy)methyl silyl oxide) silicon phthalocyanine = (MDM)2-SiPc.

Figure 4.

Figure 4

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UV–vis (dashed) and PL spectra (solid) of the (TM3)2-SiPc sample in DCM. PL excitation wavelength indicated in the top left and colored in the plot. The PL spectrum was generated on photoexcitation at 350, 610, 650, and 670 nm—peak absorption points.

Table 3. Characterization Results of the Compound (TM3)2-SiPc.

characteristic value
Ered,1 –0.95 V (irrev.)
Eox,1 (half-wave) 1.02 V
Td,5% 264 °C
Tg/Tc./Tm 223 °C/–/–
ΔHc./ΔHm –/–
λmax, abs., solution 670 nm
λmax, PL., solution 685 nm
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The reduction and oxidation potentials of (TM3)2-SiPc are similar to those observed with (3PS)2-SiPc (Figure S5, Table 3); however, the reduction potential here is irreversible, indicating the inability to oxidize the reduced sample back to neutral as a result of an electrochemical reaction. The lack of a crystallization or melting temperature in the thermal analysis is due to the flexibility, variation, and the rotational nature of the siloxane groups. The absorption spectrum (Figure 4) shows a strong Q-band transition at 670 nm and a Soret band transition at ∼350 nm, characteristic of Pcs. Figure 4 also shows the PL spectra of this compound at different excitation wavelengths. The PL excitation wavelengths were selected as the absorbance peaks in the UV–vis absorbance spectrum (350, 610, 650, and 670 nm), the same as those used with the (3PS)2-SiPc derivative. The material retains the same PL profile and thus the structure, regardless of the excitation wavelength. In addition, a Stokes shift of ∼15 nm can be observed.

Bis(bis(trimethylsiloxy) methyl silyl oxide) silicon Pc [(MDM)2-SiPc, Scheme 1] was also synthesized, but it was found that the thermal stability of this material was limited as its TGA profile (Figure S3) showed an uneven decline in mass above ∼160 °C, which could be associated with material decomposition (Td,5% = 161 °C). In comparison, the TGA profiles of (3PS)2-SiPc and (TM3)2-SiPc have a sharp decrease in weight loss, associated with material decomposition/sublimation. Therefore, due to the decreased thermal stability of (MDM)2-SiPc, it could not be purified through sublimation; thus, it could not be appropriately characterized via NMR, MS, PL, or electrochemistry to consider its organic electronic application. However, this did show the flexibility of the PR synthesis method and highlights some points to consider from a synthetic methodology point of view.

Evaluation of the PR Methodology via Direct Points of Comparison

While PR chemistry certainly can be applied to achieve siloxane and other axial derivatives of SiPcs, it was desirable to evaluate the PR methodology against other available methods for the axial functionalizing of SiPcs yielding silyloxy-SiPc derivatives that have been reported in the literature and patents and verified within our laboratory (Scheme 2). The goal was to report a process/chemistry choice of obtaining SiPc axial substituents based on the availability of the reagents for the axial substitution. The PR process outlined above and concluded will be referred to as the “PR” method in this section. The additional two methods that were investigated for points of comparison to PR chemistry were the so-called “Benoit-Grant (BG)”21 and “Aliquat (AQ)”23 methods. The “BG” method (Scheme 2) involves the reaction of a chloro-trialkyl/aryl silane with (HO)2-SiPc in pyridine at reflux.21 The (HO)2-SiPc precursor is generated via reaction of Cl2-SiPc with a nucleophilic −OH source which was developed as basic hydrolysis does not work for SiPc derivatives. The “AQ” method uses Cl2-SiPc as the starting material; circumvents the need to generate (HO)2-SiPc, with a mixture of reagents including chlorotrialkyl/aryl silane, sodium hydroxide, potassium carbonate, and an Aliquat phase-transfer catalyst in chlorobenzene; and presumably forms (HO)2-SiPc in situ.23

Scheme 2. (i) SiCl4, Quinoline, 4 h, 219 °C, under N2 (g); (ii) CsOH (50 wt % in H2O), DMF, 120 °C, 4 h under Ar; (g) (iii) “BG” Method—Chlorotri-n-butylsilane, Pyridine, 115 °C, 5 h under Ar (g); (iv) “PR” Method—Tri-n-butylsilane, B(C6F5)3, Nitrobenzene, 22 h under Ar; (v) “AQ” Method—Chlorotri-n-hexylsilane, Sodium Hydroxide, Aliquat HTA-1, Potassium Carbonate, Chlorobenzene, 132 °C under Ar.

Scheme 2

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As above, the trihexyl SiPc derivative (3HS)2-SiPc was targeted with each process to compare the yields of the three methods as the chloro and hydride derivative of trishexyl-silane is equally available. This derivative was also chosen as highly soluble and therefore easy to follow and characterize (as also outlined above). The materials made via each of the three pathways were purified using train sublimation. Table 4 notes the crude and sublimation yields of (3HS)2-SiPc using each method, with their purity confirmed. The sublimation yield was obtained by comparing the amount of the crude material that was introduced to the system to the amount of the purified material collected afterward.

Table 4. Summary of Yields of (3HS)2-SiPc Samplesa.

3HS AQ BG PR
crude yield 81% (4.32 g) 23% (0.868 g) 74% (0.733 g)
sublimation yield 80% (0.404 g) 50% (0.154 g) 83% (0.251 g)
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a

Crude yield is based on reaction. Sublimation went forward and may not have used 100% of the crude; therefore, the percentage (%) yield on sublimation and the mass (g) outlined are based on alternative amounts of crude going forward with sublimation.

Directly comparing the crude yields, the AQ method has the highest yielding process at 81%. This is followed by the PR method at 74% yield and the BG method with 23%. This would initially indicate the superiority of the AQ or PR methods, in that order, over the BG method. The sublimation yield of the BG method also has the lowest yield of the three processes, at 50%. Assuming the consistent sublimation methodology and no loss of material due to the apparatus setup, this would indicate that there was less impurity present in the PR crude sample than in the samples of the other two methods. The similarity in yield of the AQ method product also indicates a high degree of crude sample purity. Thus, in terms of (3HS)2-SiPc material yield, the BG method does not compete with the PR and AQ methods. This approach also validates the PR method equally relative to the AQ method as additional chemists, researchers, engineers, developers, etc., are considering SiPc molecular designs and process consideration.

(3BS)2-SiPc Derivative Synthesis and Characterization

Beyond yield, it was desired to study the consequential characteristics of the SiPc derivatives synthesized via the three methods (BG, AQ, and PR) to establish any process variations leading to differences in detailed material properties, despite having the same structure. For this, the tri-n-butylsilane derivative bis(tri-n-butyl silyl oxide) silicon phthalocyanine ((3BS)2-SiPc) was synthesized via the three methods due to a growing potential interest in this molecule for applications (Scheme 2). Most notably, it has potential to apply as a non-fullerene electron-accepting material within a bulk-heterojunction (BHJ) organic photovoltaic (OPV).17

The established PR methodology was used with slight modifications to accommodate the decreased solubility of the 3BS derivative as compared to the (3HS)2-SiPc. The synthesis of (3BS)2-SiPc also achieved full conversion using the PR process (as established by TLC). The (3BS)2-SiPc derivative was then also synthesized using the BG and AQ processes and purified using a train sublimation. Their crude and sublimation yields are listed in Table 5. The three samples were characterized by NMR analysis (Figures S8–S10), MS analysis (Figures S11–S13), and thermal analysis.

Table 5. Summary of Yields and Properties of (3BS)2-SiPc Samples.

3BS AQ BG PR
crude yield 57% (2.61 g) 81% (1.69 g) ≪50% (0.86 g)
sublimation yield 91% (0.29 g) 59% (0.2 g) 48% (0.139 g)
Td, 5% 293 °C 281 °C 289 °C
Tm,1/Tm,2 63 °C/234 °C 63 °C/234 °C 63 °C/234 °C
ΔHm,1/ΔHm,2 (J/g) 29.7/40.4 35.4/23.7 38.6/38.6
Tc,1/Tc,2 63 °C/212 °C 61 °C/200 °C 62 °C/196 °C
ΔHc,1/ΔHc,2 (J/g) 25.6/44.2 33.5/38.6 33.9/39.4
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Based on the collected data on the synthesis of (3BS)2-SiPc, the BG process now has the highest crude yield, compared to the 3HS derivative results. The AQ process has a lower yield at 57%, while the PR process crude yield is under 50%. The PR crude yield is under 50% as the workup procedure did not remove all the excess tri-butyl-silane. The sublimation purification process yields indicate that the AQ process has the highest material purity, with a 91% sublimation yield. Both the BG process and PR process materials were less pure as 59 and 48%, respectively, of the material were collected from sublimation. This indicates that in both cases with 3HS and 3BS, the AQ method produces a higher-purity material over the BG and PR methods. Additionally, it can be surmised that the yield of the PR method depends on the solubility of the derivative (3HS more soluble than 3BS).

The thermal properties of these three samples were studied to examine the effect of the synthetic process on morphology. The TGA results (Figure 5a) reveal different 5% mass loss temperatures (Td,5%). The AQ sample is modestly most thermally stable, closely followed by the PR and then BG samples. All three compounds have virtually identical degradation profiles.

Figure 5.

Figure 5

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(a) TGA trace of three (3BS)2SiPc compounds synthesized by different methods; (b) DSC trace of all three (3BS)2SiPc samples on the first cooling ramp of a heat/cool/heat cycle; (c) DSC trace of all three (3BS)2SiPc samples on the second heating ramp of a heat/cool/heat cycle.

The DSC results (Figure 5b,c) yield additional information on the melting and crystallization properties of these SiPc derivatives, including their melting temperature (Tm), crystallization temperature (Tc), enthalpy of melting (ΔHm), and enthalpy of crystallization (ΔHc). The enthalpy values were obtained by integrating the DSC traces at the identified temperatures. For all three compounds, two melt/crystallization transitions were observed. The first transition occurred at approximately 63 °C and was consistent between heating and cooling curves across all three compounds. The enthalpies associated with this transition point were also very similar in each series but slightly different across the series (AQ – ΔHc,1 ≈ ΔHm,1 ≈ 28 J/g, BG – ΔHc,1 ≈ ΔHm,1 ≈ 34 J/g, PR – ΔHc,1 ≈ ΔHm,1 ≈ 36 J/g).

The second transition temperature was more varied between heating and cooling curves across all series (ranging as much as 38 °C in the PR series between heating and cooling curves), indicating a path-dependent (i.e., heating vs cooling) effect on the melting transition. The enthalpies associated with this transition point were similar in AQ and PR series but widely differing for BG (AQ – ΔHc,2 ≈ ΔHm,2 ≈ 42 J/g, BG – ΔHc,2 ≈ 39 J/g & ΔHm,2 ≈ 24 J/g, PR – ΔHc,2 ≈ ΔHm,2 ≈ 39 J/g). The disparity observed with BG can possibly be explained by potential impurities present in the sample or structural defects, thus lowering the energy required for a melt transition, at elevated temperatures.

Based on this thermal characterization study, the PR method generates a batch of (3BS)2SiPcs that is very similar to batches generated by the other two methods and thus can be considered a comparable method for SiPc functionalization. The main differences being observed between the three batches were in their enthalpies and second crystallization temperatures.

Conclusions

This study outlines the first ever use of PR chemistry to axially functionalize a silicon phthalocyanine (SiPc). This method has been shown to be applicable to a variety of alkyl/aryl axial substituent derivatives, without the byproduct formation of a Tbc derivative. The triphenylsilane derivative, (3PS)2-SiPc, being the first example was synthesized and characterized by CV, TGA/DSC, NMR, MS, UV–vis, and PL spectroscopy.

In addition, PR chemistry has been shown here to enable the synthesis of siloxane-functionalized derivatives via commercially available silanes. However, the synthesis of a tris(trimethylsiloxy) derivative, (TM3)2-SiPc, resulted in a mixture of products and the synthesis of a bis(dimethylsiloxy)methyl derivative. Now, this mixture formed was not clear but is just an observation to note. The formation of (MDM)2-SiPc, was successful; the compound was however thermally unstable and unable to be purified and is just another observation to note as one considers the PR process for Pc derivatives.

A PR process-derived SiPc was also compared against two other SiPc functionalization methods (BG and AQ). The comparison demonstrated that the PR reaction is capable of synthesizing a derivative that has very similar thermal characteristics to the same derivative synthesized via the two other methods. This ascertains PR chemistry as a viable means to functionalize SiPcs. This also brings out the hidden potential of PR chemistry to access certain Pc products/derivatives that are whether derivatives that have been previously obtainable by alternative processes or derivatives that are now only accessible via the PR method.

Experimental Section

Materials

All materials were obtained from Sigma-Aldrich, except 1,3-diiminoisoindoline, which was obtained from Xerox Corp. (Mississauga, ON, Canada). Chlorotri-n-hexylsilane, chlorotri-n-butylsilane, tri-n-hexylsilane, tri-n-butylsilane, and triphenylsilane were obtained from Gelest, Inc. (Pennsylvania, USA), and tris(pentaphenylfluoro)borane was obtained from Strem Inc. (Massachusetts, USA). Solvents were obtained from Caledon (Caledon, Ontario, Canada). All materials were used as received without further purification.

TLC was performed on aluminum plates coated with silica (a pore size of 60 Å) and a fluorescent indicator, obtained from Whatman Ltd., and visualized under UV (254 nm) light.

Dichloro-Silicon Phthalocyanine (Cl2-SiPc)

Cl2-SiPc was synthesized according to the literature.69 For example, to an oven-dried three-neck round-bottom flask were added 1,3-diiminoisoindoline (12.00 g, 0.082 mol) and quinoline (94.6 mL). The mixture was heated to 50 °C for 15 min under N2, and then, SiCl4 (9.46 mL, 0.082 mol) was added via a syringe. The reaction mixture was then heated to 219 °C for 4 h. The reaction mixture was then cooled to 185 °C and vacuum-filtered hot. The residue was then washed with 50 mL of quinoline, 150 mL of toluene, 250 mL of methanol, and 150 mL of acetone. The material was vacuum-oven-dried overnight at 80 °C to yield a shiny purple powder (crude yield = 82%).

Bis(hydroxy)-Silicon Phthalocyanine ((HO)2-SiPc)

(HO)2-SiPc was synthesized according to the literature.10 To an oven-dried three-neck round-bottom flask were added Cl2-SiPc (2.5 g, 4.09 mmol), dimethylformamide (25 mL), and cesium hydroxide (50 wt % solution in H2O) (1.50 g, 10.0 mmol) under argon. The reaction mixture was heated to 120 °C for 4 h. The crude product was precipitated into methanol and filtered to give a dark-blue powder (crude yield = 94%), which was used without further purification. LRMS (EI) m/z: [M] calcd for 574.15; found, 574.1.

Bis(tri-n-hexylsilyl Oxide) Silicon Phthalocyanine, “PR” Method, PR-(3HS)2-SiPc

To an oven-dried pressure vessel flask were added (HO)2SiPc (0.5 g, 0.86 mmol) and nitrobenzene (28 mL). Argon gas was bubbled through the solution for 2 min. Tri-n-hexylsilane (2.41 g, 8.63 mmol) and tris(pentaphenylfluoro)borane (30.7 mg, 0.06 mmol) via the stock solution were added, and the vessel was submerged into an oil bath at 100 °C. A dose of 30.7 mg of tris(pentaphenylfluoro)borane (via the stock solution) and 2.41 g of tri-n-hexylsilane were added after 2.5 h and 5 h of reaction time. The reaction progress was monitored via silica TLC plates using a 1:1 hexanes/THF system. The reaction was then cooled to room temperature. Nitrobenzene was removed via rotary evaporation, and then, the residual solid was washed with 20 mL of pentane. The solid was then collected and dried in a vacuum oven overnight at 80 °C to yield a dark-blue shimmery powder (crude yield = 74%). The material was purified via train sublimation prior to use.

Bis(triphenyl Silyl Oxide) Silicon Phthalocyanine, (3PS)2-SiPc

To an oven-dried pressure vessel flask were added (HO)2SiPc (0.3 g, 0.52 mmol) and nitrobenzene (17 mL). Argon gas was bubbled through the solution for 2 min. Triphenylsilane (1.35 g, 5.2 mmol) and tris(pentaphenylfluoro)borane (18.9 mg, 0.037 mmol) via the stock solution were added, and the vessel was submerged into an oil bath at 100 °C. A dose of 18.9 mg of tris(pentaphenylfluoro)borane (via the stock solution) and 1.35 g of triphenylsilane were added after 2.5, 5, and 7.5 h of reaction time. The reaction was monitored via silica TLC plates using a 1:1 hexanes/THF system. The reaction was then left for an additional 15 h before cooling to room temperature. Nitrobenzene was removed via rotary evaporation, and then, the residual solid was washed with 10 mL of pentane. The solid was then collected and dried in a vacuum oven overnight at 80 °C to yield a dark-aquamarine-blue powder (crude yield, incl. excess, unremoved triphenylsilane = 178%). The material was purified via train sublimation prior to use. LRMS (EI) m/z: [M] calcd, for 1092.32; found, 1092.3. 1HNMR (500 MHz, CDCl3): δ 9.45 ppm(8 H, s), 8.29 (8H, s), 6.68 (6 H, m), 6.28(12H, m), 4.78(12H, m).

Bis(tris(trimethylsiloxy) Silyl Oxide) Silicon Phthalocyanine, (TM3)2-SiPc

To an oven-dried pressure vessel flask were added (HO)2SiPc (0.3 g, 0.52 mmol) and nitrobenzene (17 mL). Argon gas was bubbled through the solution for 2 min. Tris(trimethysiloxy)silane (1.55 g, 5.2 mmol) and tris(pentaphenylfluoro)borane (18.9 mg, 0.037 mmol) via the stock solution were added, and the vessel was submerged into an oil bath at 100 °C. A dose of 18.9 mg of tris(pentaphenylfluoro)borane (via the stock solution) and 1.55 g of tris(trimethylsiloxy)silane were added after 2.5, 5, and 7.5 h of reaction time. The reaction was monitored via silica TLC plates using a 1:1 hexanes/THF system. The reaction was then left for an additional 15 h before cooling to room temperature. The solution was then rotovapped to dryness. The solid was then collected and dried in a vacuum oven overnight at 80 °C to yield a dark-blue powder (crude yield = 80%). The material was purified via train sublimation prior to use. LRMS (EI) m/z: [M] calcd, for 1092.32; found, 1092.3. 1HNMR (500 MHz, C6D6): δ 9.77 ppm (4 H, q), 9.74 (8H, q), 9.71 (8H, q), 7.96 (4H, q), 7.93 (4H, q), 7.91(4H, q), −0.91 (m, 42 H), −0.97 (m, 42 H).

Bis((bis(trimethylsiloxy)methyl) Silyl Oxide) Silicon Phthalocyanine, (MDM)2-SiPc

To an oven-dried pressure vessel flask were added (HO)2SiPc (0.3 g, 0.52 mmol) and nitrobenzene (17 mL). Argon gas was bubbled through the solution for 2 min. Bis(trimethysiloxy)methylsilane (1.17 g, 5.2 mmol) and tris(pentaphenylfluoro)borane (18.9 mg, 0.037 mmol) via the stock solution were added, and the vessel was submerged into an oil bath at 100 °C. A dose of 18.9 mg of tris(pentaphenylfluoro)borane (via the stock solution) and 1.55 g of bis(trimethylsiloxy)methylsilane were added after 2.5, 5, and 7.5 h of reaction time. The reaction was monitored via silica TLC plates using a 1:1 hexanes/THF system. The reaction was then left for an additional 15 h before cooling to room temperature. The solution was then rotovapped to dryness. The solid was then collected and dried in a vacuum oven overnight at 80 °C to yield shiny purple-blue crystalline shards (crude yield = 86%). LRMS (EI) m/z: [M] calcd, for 1016.30; found, 1014.3.

Bis(tri-n-hexyl Silyl Oxide) Silicon Phthalocyanine, “AQ” Method, AQ-(3HS)2-SiPc

AQ-(3HS)2-SiPc was synthesized according to the literature.23 For example, 2.87 g (4.7 mmol) of Cl2-SiPc, 4.93 g (5.0 mmol) of chlorotri-n-hexylsilane, 1.00 g (25.0 mmol) of sodium hydroxide (crushed pellets), 0.04 g of Aliquat HTA-l (Cognis), and 25 mL of chlorobenzene were heated to 132 °C under reflux. After 1 h and 2 h, respectively, another 1.64 g (5.0 mmol) of chlorotri-n-hexylsilane and 1.64 g (5.0 mmol) of chlorotri-n-hexylsilane and 0.40 g (10 mmol) of sodium hydroxide (crushed pellets) were added. After reaction for an additional 4 h, the solution was cooled to room temperature. The solution was filtered, and the filtrate was concentrated to dryness and then precipitated into methanol. The precipitate was filtered via vacuum filtration, washed with methanol and water, and dried at 50 °C under reduced pressure to yield a shiny blue powder (crude yield = 81%). The material was purified via train sublimation prior to use.

Bis(tri-n-hexyl Silyl Oxide) Silicon Phthalocyanine, “BG” Method, BG-(3HS)2-SiPc

BG-(3HS)2-SiPc was synthesized according to the literature.10,23 For example, 2.24 g (3.9 mmol) of (HO)2-SiPc, 13.06 g (39.7 mmol) of chlorotri n-hexylsilane, and 225 mL of pyridine were combined in an oven-dried round-bottom flask and heated to 115 °C for 5 h. After cooling to room temperature, the solution was filtered, and the filtrate was concentrated and mixed with pentane. The precipitate was then washed with pentane, acetone, and water and dried at 50 °C under reduced pressure overnight to yield a dark-blue powder (crude yield = 23%). The material was purified via train sublimation prior to use.

Bis(tri-n-butyl Silyl Oxide) Silicon Phthalocyanine, “AQ” Method, AQ-(3BS)2-SiPc

AQ-(3BS)2SiPc was synthesized according to the literature.23 For example, a solution of 3.63 g (15.0 mmol) of tri-n-butylchlorosilane, 0.94 g (23.5 mmol) of sodium hydroxide (crushed pellets), and 0.04 g of Aliquat HTA-l (Cognis) in 25 mL of chlorobenzene was stirred at room temperature. After 3 h, 2.87 g (4.7 mmol) of Cl2-SiPc and 1.63 g (11.8 mmol) of potassium carbonate were added. The reaction mixture was heated to 132 °C under reflux. After additional 1 and 2 h, 1.21 g (5.0 mmol) of tri-n-butylchlorosilane was added in each case. After the second addition of tri-n-butylchlorosilane, the reaction was left for an additional 4 h. The solution was cooled to room temperature and gravity-filtered. The filtrate was concentrated, and the residue was stirred with 10 mL of methanol, filtered with suction, washed with methanol and water, and dried at 50 °C under reduced pressure overnight to obtain a shiny blue powder (crude yield = 57%). The material was purified via train sublimation prior to use. LRMS (EI) m/z: [M] calcd, for 972.51; found, 972.5. 1HNMR (500 MHz, C6D6): δ 9.74 ppm (8 H, m), 7.90 (8H, m), 0.28(30 H, m), −0.99(12 H, m), −2.09(12H, m).

Bis(tri-n-butyl Silyl Oxide) Silicon Phthalocyanine, “BG” Method, BG-(3BS)2-SiPc

BG-(3BS)2SiPc was synthesized according to the literature.10,23 For example, to an oven-dried three-neck round-bottom flask were added (HO)2SiPc, tri-n-butylchlorosilane, and pyridine under nitrogen. The mixture was stirred and heated to 115 °C for 5 h and then cooled to room temperature. The mixture was gravity-filtered. The filtrate was concentrated and precipitated into methanol. The precipitate was collected and dried overnight in a vacuum oven to yield a dark-blue, dull powder (crude yield = 81%). LRMS (EI) m/z: [M] calcd, for 972.51; found, 972.5. 1HNMR (500 MHz, C6D6): δ 9.74 ppm (8 H, m), 7.90 (8H, m), 0.28(30 H, m), −0.99(12 H, m), −2.09(12H, m).

Bis(tri-n-butyl Silyl Oxide) Silicon Phthalocyanine, “PR” Method, PR-(3BS)2-SiPc

To an oven-dried pressure vessel flask were added (HO)2SiPc (0.5 g, 0.86 mmol) and nitrobenzene (28 mL). Argon gas was bubbled through the solution for 2 min. Tri-n-butylsilane (1.73 g, 8.63 mmol) and tris(pentafluorophenyl)borane (30.7 mg, 0.06 mmol) via the stock solution were added, and the vessel was submerged into an oil bath at 100 °C. A dose of 30.7 mg of tris(pentafluorophenyl)borane (via the stock solution) and 1.73 g of tri-n-butylsilane were added after 2.5, 5, and 7.5 h of reaction time. The reaction was monitored via silica TLC plates using a 1:1 hexanes/THF system. The reaction was then left for an additional 15 h before cooling to room temperature. Nitrobenzene was removed via rotary evaporation, and then, the residual solid was washed with 10 mL of pentane. The solid was then collected and dried in a vacuum oven overnight at 80 °C to yield a dark-blue shimmery powder (crude yield = 102%). The material was purified via train sublimation prior to use. LRMS (EI) m/z [M] calcd, for 972.51; found, 972.5. 1HNMR (500 MHz, C6D6): δ 9.74 ppm (8 H, m), 7.90 (8H, m), 0.28(30 H, m), −0.99(12 H, m), −2.09(12H, m).

Methods

NMR spectra were recorded on an Agilent DD2 500 spectrometer at 23 °C in CDCl3, operating at 500 MHz for 1H NMR. Spin multiplicities are designated by the following abbreviations: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), and br (broad). Low-resolution mass spectroscopy (LRMS) was performed on a GC Premier TOF mass spectrometer (Waters Corporation, Milford, Massachusetts, USA) with EI/CI sources or an AccuTOF model JMS-T1000LC mass spectrometer (JEOL USA Inc., Peabody, Massachusetts, USA) equipped with a Direct Analysis in Real Time (DART) ion source.

Ultraviolet–visible (UV–vis) absorption spectra were recorded on a PerkinElmer Lambda 25 UV–vis spectrometer using a PerkinElmer quartz cuvette with a 10 mm path length in DCM. PL spectra were recorded on a PerkinElmer LS55 fluorescence spectrometer in DCM.

Electrochemistry was performed in a deoxygenated solvent (DCM) using a platinum wire counter electrode and a Ag/AgCl reference electrode. Tetrabutylammonium perchlorate (1 M) was used as the supporting electrolyte, and decamethylferrocene was used as an internal reference.

TGA (Q50 TA Instruments) was used to characterize the thermal properties under a blanket of nitrogen with a platinum boat. A heating rate of 5 °C min–1 was used with the Ramp method until the desired temperature was reached. DSC was performed using a DSC Q1000 (TA Instruments) and was performed in the Heat Cool Heat mode, with a heating rate of 10 °C min–1.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.1c02738.

  • TGA/DSC traces, CV traces, UV–vis absorbance spectrum, NMR, and MS data (PDF)

T.B. and B.L. would like to acknowledge the Natural Sciences and Engineering Research Council of Canada for their funding support through the Discovery Grant program.

The authors declare no competing financial interest.

Supplementary Material

ao1c02738_si_001.pdf (1.2MB, pdf)

References

  1. de la Torre G.; Claessens C. G.; Torres T. Phthalocyanines: old dyes, new materials. Putting color in nanotechnology. Chem. Commun. 2007, 20, 2000–2015. 10.1039/b614234f. [DOI] [PubMed] [Google Scholar]
  2. Plint T.; Lessard B. H.; Bender T. P. Assessing the potential of group 13 and 14 metal/metalloid phthalocyanines as hole transport layers in organic light emitting diodes. J. Appl. Phys. 2016, 119, 145502. 10.1063/1.4945377. [DOI] [Google Scholar]
  3. Zysman-Colman E.; Ghosh S. S.; Xie G.; Varghese S.; Chowdhury M.; Sharma N.; Cordes D. B.; Slawin A. M. Z.; Samuel I. D. W. Solution-Processable Silicon Phthalocyanines in Electroluminescent and Photovoltaic Devices. ACS Appl. Mater. Interfaces 2016, 8, 9247–9253. 10.1021/acsami.5b12408. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Melville O. A.; Grant T. M.; Mirka B.; Boileau N. T.; Park J.; Lessard B. H. Ambipolarity and Air Stability of Silicon Phthalocyanine Organic Thin-Film Transistors. Adv. Electron. Mater. 2019, 5, 1900087. 10.1002/aelm.201900087. [DOI] [Google Scholar]
  5. Melville O. A.; Grant T. M.; Lessard B. H. Silicon phthalocyanines as N-type semiconductors in organic thin film transistors. J. Mater. Chem. C 2018, 6, 5482–5488. 10.1039/c8tc01116h. [DOI] [Google Scholar]
  6. Lessard B. H.; Grant T. M.; White R.; Thibau E.; Lu Z.-H.; Bender T. P. The position and frequency of fluorine atoms changes the electron donor/acceptor properties of fluorophenoxy silicon phthalocyanines within organic photovoltaic devices. J. Mater. Chem. A 2015, 3, 24512–24524. 10.1039/c5ta07173a. [DOI] [Google Scholar]
  7. Lessard B. H.; White R. T.; AL-Amar M.; Plint T.; Castrucci J. S.; Josey D. S.; Lu Z.-H.; Bender T. P. Assessing the Potential Roles of Silicon and Germanium Phthalocyanines in Planar Heterojunction Organic Phtovoltaic Devices and How Pentafluoro Phenoxylation Can Enhance pi-pi interactions and Device Performance. ACS Appl. Mater. Interfaces 2015, 7, 5076–5088. 10.1021/am508491v. [DOI] [PubMed] [Google Scholar]
  8. Ke L.; Min J.; Adam M.; Gasparini N.; Hou Y.; Perea J. D.; Chen W.; Zhang H.; Fladischer S.; Sale A.-C.; Spiecker E.; Tykwinski R. R.; Brabec C. J.; Ameri T. A Series of Pyrene-Substituted Silicon Phthalocyanines as Near-IR Sensitizers in Prganic Ternary Solar Cells. Adv. Energy Mater. 2016, 6, 1502355. 10.1002/aenm.201502355. [DOI] [Google Scholar]
  9. Honda S.; Nogami T.; Ohkita H.; Benten H.; Ito S. Improvement of the Light-Harvesting Efficiency in Polymer/Fullerene Bulk-Heterojunction Solar Cells by Interfacial Dye Modification. ACS Appl. Mater. Interfaces 2009, 1, 804–810. 10.1021/am800229p. [DOI] [PubMed] [Google Scholar]
  10. Lessard B. H.; Dang J. D.; Grant T. M.; Gao D.; Seferos D. S.; Bender T. P. Bis(tri-n-hexylsilyl oxide) Silicon Phthalocyanine: A Unique Additive in Ternary Bulk Heterojunction Organic Photovoltaic Devices. ACS Appl. Mater. Interfaces 2014, 6, 15040–15051. 10.1021/am503038t. [DOI] [PubMed] [Google Scholar]
  11. Grant T. M.; Gorisse T.; Dautel O.; Wantz G.; Lessard B. H. Multifunctional ternary additive in bulk heterojunction OPV: increased performance and stability. J. Mater. Chem. A 2017, 5, 1581–1587. 10.1039/c6ta08593h. [DOI] [Google Scholar]
  12. Ke L.; Gasparini N.; Min J.; Zhang H.; Adam M.; Rechberger S.; Forberich K.; Zhang C.; Spiecker E.; Tykwinski R. R.; Brabec C. J.; Ameri T. Panchromic ternary/quaternary polymer/fullerene BHJ solar cells based on novel silicon napthalocyanine and silicon phthalocyanine dye sensitizers. J. Mater. Chem. A 2017, 5, 2550–2562. 10.1039/c6ta08729a. [DOI] [Google Scholar]
  13. Do Kim H.; Ohkita H.; Benten H.; Ito S. Dye Sensitization in Polymer/ZnO/Dye Ternary Hybrid Solar Cells. Chem. Lett. 2013, 42, 825–827. 10.1246/cl.130265. [DOI] [Google Scholar]
  14. Honda S.; Ohkita H.; Benten H.; Ito S. Selective Dye Loading at the Heterojunction in Polymer/Fullerene Solar Cells. Adv. Energy Mater. 2011, 1, 588–598. 10.1002/aenm.201100094. [DOI] [Google Scholar]
  15. Xu H.; Ohkita H.; Tamai Y.; Benten H.; Ito S. Interface Engineering for Ternary Blend Polymer Solar Cells with a Heterostructured Near-IR Dye. Adv. Mater. 2015, 27, 5868–5874. 10.1002/adma.201502773. [DOI] [PubMed] [Google Scholar]
  16. Dang M.-T.; Grant T. M.; Yan H.; Seferos D. S.; Lessard B. H.; Bender T. P. Bis(tri-n-alkylsilyl oxide) silicon phthalocyanines: a start to establishing a structure property relationship as both ternary additives and non-fullerene electron acceptors in bulk heterojunction organic photovoltaic devices. J. Mater. Chem. A 2017, 5, 12168–12182. 10.1039/c6ta10739g. [DOI] [Google Scholar]
  17. Vebber M. C.; Grant T. M.; Brusso J. L.; Lessard B. H. Bis(trialkylsilyl oxide) Silicon Phthalocyanines: Understanding the Role of Solubility in Device Performance as Ternary Additives in Organic Photovoltaics. Langmuir 2020, 36, 2612–2621. 10.1021/acs.langmuir.9b03772. [DOI] [PubMed] [Google Scholar]
  18. Lim B.; Margulis G. Y.; Yum J.-H.; Unger E. L.; Hardin B. E.; Grätzel M.; McGehee M. D.; Sellinger A. Silicon-Napthalo/Phthalocyanine-Hybrid Sensitizer for Efficient Red Response in Dye-Sensitized Solar Cells. Org. Lett. 2013, 15, 784–787. 10.1021/ol303436q. [DOI] [PubMed] [Google Scholar]
  19. Martín-Gomisa L.; Barea E. M.; Fernández-Lázaroa F.; Bisquert J.; Sastre-Santos Á. Dye sensitized solar cells using non-aggregated silicon phthalocyanines. J. Porphyrins Phthalocyanines 2011, 15, 1004–1010. 10.1142/s1088424611003914. [DOI] [Google Scholar]
  20. Xu H.; Wada T.; Ohkita H.; Benten H.; Ito S. Dye sensitization of polymer/fullerene solar cells incorporating bulky phthalocyanines. Electrochim. Acta 2013, 100, 214–219. 10.1016/j.electacta.2012.05.155. [DOI] [Google Scholar]
  21. Wheeler B. L.; Nagasubramanian G.; Bard A. J.; Schechtman L. A.; Kenney M. E.; Kenney M. E. A Silicon Phthalocyanine and a Silicon Napthalocyanine: Synthesis, Electrochemistry, and Electrogenerated Chemiluminescence. J. Am. Chem. Soc. 1984, 106, 7404–7410. 10.1021/ja00336a019. [DOI] [Google Scholar]
  22. Chen Y.; Gao L.; Feng M.; Gu L.; He N.; Wang J.; Araki Y.; Blau W.; Ito O. Photophysical and Optical Limiting Properties of Axially Modified Phthalocyanines. Mini-Rev. Org. Chem. 2009, 6, 55–65. 10.2174/157019309787316166. [DOI] [Google Scholar]
  23. Gessner T.; Sens R.; Ahlers W.; Vamvakaris C.. Preparation of Silicon Phthalocyanines and Germanium Phthalocyanines and Related Substances. U.S. Patent 20,100,113,767 A12010.
  24. Furuyama T.; Ishii T.; Ieda N.; Maeda H.; Segi M.; Uchiyama M.; Nakagawa H. Cationic axial ligands on sulfur substituted silicon(iv) phthalocyanines: improved hydrophilicity and exceptionally red-shifted absorption into the NIR region. Chem. Commun. 2019, 55, 7311–7314. 10.1039/c9cc03022k. [DOI] [PubMed] [Google Scholar]
  25. Lau J. T. F.; Jiang X.-J.; Ng D. K. P.; Lo P.-C. A disulfide-linked conjugate of ferrocenyl chalcone and silicon(iv) phthalocyanine as an activatable photosensitiser. Chem. Commun. 2013, 49, 4274–4276. 10.1039/c2cc37251g. [DOI] [PubMed] [Google Scholar]
  26. Guilleme J.; Martínez-Fernández L.; Corral I.; Yáñez M.; González-Rodríguez D.; Torres T. Direct Access to Axially Substituted Subphthalocyanines from Trimethylsilyl-Protected Nucleophiles. Org. Lett. 2015, 17, 4722–4725. 10.1021/acs.orglett.5b02213. [DOI] [PubMed] [Google Scholar]
  27. Ciliberto E.; Doris K. A.; Pietro W. J.; Reisner G. M.; Ellis D. E.; Fragala I.; Herbstein F. H.; Ratner M. A.; Marks T. J. The .pi.-.pi. interactions and bandwidths in molecular metals. A chemical, structural, photoelectron spectroscopic, and Hartree-Fock-Slater study of monomeric and cofacially joined dimeric silicon phthalocyanines. J. Am. Chem. Soc. 1984, 106, 7748–7761. 10.1021/ja00337a018. [DOI] [Google Scholar]
  28. Silver J.; Frampton C. S.; Fern G. R.; Davies D. A.; Miller J. R.; Sosa-Sanchez J. L. Novel Seven Coordination Geometry of Sn(IV): Crystal Structures of Phthalocyaninato Bis(undecylcarboxylato)Sn(IV), Its Si(IV) Analogue, and Phthalocyaninato Bis(chloro)silicon(IV). The Electrochemistry of the Si(IV) Analogue and Related Compounds. Inorg. Chem. 2001, 40, 5434–5439. 10.1021/ic001120a. [DOI] [PubMed] [Google Scholar]
  29. Miao P.; Robinson A. W.; Palmer R. E.; Kariuki B. M.; Harris K. D. M. Structural Properties of Self-Organized Organo-Silicon Macromolecular Films Investigated by Scanning Tunneling Microscopy and X-ray Diffraction. J. Phys. Chem. B 2000, 104, 1285–1291. 10.1021/jp993167r. [DOI] [Google Scholar]
  30. Wagner H. J.; Loutfy R. O.; Hsiao C.-K. Purification and characterization of phthalocyanines. J. Mater. Sci. 1982, 17, 2781–2791. 10.1007/BF00644652. [DOI] [Google Scholar]
  31. Zhang X.-F. Tetrabenzotriazacorrole: Its synthesis, reavitivty, physical properties, and applications. Coord. Chem. Rev. 2015, 285, 52–64. 10.1016/j.ccr.2014.11.002. [DOI] [Google Scholar]
  32. Zhang X.-F.; Rong Y. Silicon tetrabenzotriaza corrole and silicon phthalocyanine: Synthesis, photophysics and singlet oxygen generation. J. Photochem. Photobiol., A 2011, 222, 141–145. 10.1016/j.jphotochem.2011.05.013. [DOI] [Google Scholar]
  33. Kobayashi N.; Furuya F.; Yug G.-C.; Wakita H.; Yokomizo M.; Ishikawa N. Synthesis and Characterization of Phthalocyanines with Direct Si–Si Linkages. Chem.—Eur. J. 2002, 8, 1474–1484. . [DOI] [PubMed] [Google Scholar]
  34. Kobayashi N.; Yokoyama M.; Muranaka A.; Ceulemans A. Formation of silicon triazacorrole and tetrabenzotriazacorrole by the ring contraction of the corresponding tetraazaporphyrin ligands. Tetrahedron Lett. 2004, 45, 1755–1758. 10.1016/j.tetlet.2003.12.083. [DOI] [Google Scholar]
  35. Raboui H.; Lough A. J.; Szawiola A. M.; Bender T. P. Versatile synthesis of siloxy silicon tetrabenzotriazacorroles and insight into the mode of the macrocycle formation. Inorg. Chem. 2018, 57, 5174–5182. 10.1021/acs.inorgchem.8b00181. [DOI] [PubMed] [Google Scholar]
  36. Raboui H.; Thibau E. S.; Josey D. S.; Lu Z.-H.; Bender T. P. Oxy phosphorus tetrabenzotriazacorrole: firming up the chemical structure and identifying organic photovoltaic functionality to leverage its unique dual absorbance. J. Mater. Chem. A 2017, 5, 10978–10985. 10.1039/c7ta02496g. [DOI] [Google Scholar]
  37. Daziano J. P.; Steenken S.; Chabannon C.; Mannoni P.; Chanon M.; Julliard M. Photophysical and Redox Properties of a Series of Phthalocyanines: Relation wiht Their Photodynamic Activities on TF-1 and Daudi Leukemic Cells. Photochem. Photobiol. 1996, 64, 712–719. 10.1111/j.1751-1097.1996.tb03129.x. [DOI] [PubMed] [Google Scholar]
  38. Brook M. A. New Control Over Silicone Synthesis using SiH Chemistry: The Piers-Rubinsztajn Reaction. Chem.—Eur. J. 2018, 24, 8458–8469. 10.1002/chem.201800123. [DOI] [PubMed] [Google Scholar]
  39. Gretton M. J.; Kamino B. A.; Bender T. P. Extension of the Application of Piers-Rubinsztajn Conditions to Produce Triarylamine Pendant Dimethylsiloxane Copolymers. Macromol. Symp. 2013, 324, 82–94. 10.1002/masy.201200071. [DOI] [Google Scholar]
  40. Gretton M. J.; Kamino B. A.; Brook M. A.; Bender T. P. The Use of Piers-Rubinsztajn Conditions for the Placement of Triarylamines Pendant to Silicone Polymers. Macromolecules 2012, 45, 723–728. 10.1021/ma202041u. [DOI] [Google Scholar]
  41. Kamino B. A.; Szawiola A. M.; Plint T.; Bender T. P. Formation and application of electrochemically active cross-linked triarylamine-siloxane films using the Piers-Rubinsztajn reaction. Can. J. Chem. 2019, 97, 378–386. 10.1139/cjc-2018-0071. [DOI] [Google Scholar]
  42. Kamino B. A.; Bender T. P. The use of siloxanes, silsesquioxanes, and silicones in organic semiconducting materials. Chem. Soc. Rev. 2013, 42, 5119–5130. 10.1039/c3cs35519e. [DOI] [PubMed] [Google Scholar]
  43. Kamino B. A.; Grande J. B.; Brook M. A.; Bender T. P. Siloxane-Triarylamine Hybrids: Discrete Room Temperature Liquid Triarylamines via the Piers-Rubinsztajn Reaction. Org. Lett. 2011, 13, 154–157. 10.1021/ol102607v. [DOI] [PubMed] [Google Scholar]
  44. Kamino B. A.; Mills B.; Reali C.; Gretton M. J.; Brook M. A.; Bender T. P. Liquid Triarylamines: The Scope and Limitations of Piers–Rubinsztajn Conditions for Obtaining Triarylamine–Siloxane Hybrid Materials. J. Org. Chem. 2012, 77, 1663–1674. 10.1021/jo2020906. [DOI] [PubMed] [Google Scholar]
  45. Gale C. B.; Chin B.; Tambe C.; Graiver D.; Brook M. A. Silicone Structurants for Soybean Oil: Foams, Elastomers, and Candles. ACS Sustainable Chem. Eng. 2019, 7, 1347–1352. 10.1021/acssuschemeng.8b05047. [DOI] [Google Scholar]
  46. Grande J. B.; Fawcett A. S.; McLaughlin A. J.; Gonzaga F.; Bender T. P.; Brook M. A. Anhydrous formation of foamed silicone elastomers using the Piers-Rubinsztajn reaction. Polymer 2012, 53, 3135–3142. 10.1016/j.polymer.2012.05.033. [DOI] [Google Scholar]
  47. Zhang J.; Liang S.; Yu L.; Ladegaard Skov A.; Etmimi H. M.; Mallon P. E.; Adronov A.; Brook M. A. Silicone-Modified Graphene Oxide Fillers via the Piers-Rubinsztajn Reaction. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2379–2385. 10.1002/pola.28112. [DOI] [Google Scholar]
  48. Zhang J.; Chen Y.; Sewell P.; Brook M. A. Utilization of softwood lignin as both crosslinker and reinforcing agent in silicone elastomers. Green Chem. 2015, 17, 1811–1819. 10.1039/c4gc02409e. [DOI] [Google Scholar]
  49. Peng J.; Bai Y.; Li J. Piers-Rubinsztajn Reaction and the Application in Siloxane/Polysiloxane Chemistry. Lett. Org. Chem. 2019, 16, 525–530. 10.2174/1570178615666181016114942. [DOI] [Google Scholar]
  50. Szawiola A. M.; de Melo Souza N.; Lessard B. H.; Bender T. P. Phenoxylated siloxane-based polymers via the Piers-Rubinsztajn process. Polym. Int. 2017, 66, 1324–1328. 10.1002/pi.5396. [DOI] [Google Scholar]
  51. Chen X.; Fang L.; Wang J.; He F.; Chen X.; Wang Y.; Zhou J.; Tao Y.; Sun J.; Fang Q. Intrinsic High Refractive Index Siloxane-Sulfide Polymer Networks Having High Thermostability and Transmittance via Thiol-Ene Cross-Linking Reaction. Macromolecules 2018, 51, 7567–7573. 10.1021/acs.macromol.8b01586. [DOI] [Google Scholar]
  52. Tao Y.; Zhou J.; Fang L.; Wang Y.; Chen X.; Chen X.; Hou J.; Sun J.; Fang Q. Fluoro-containing Polysiloxane Thermoset with Good Thermostability and Acid Resistance Based on the Renewable Multifunctional Vanillin. ACS Sustainable Chem. Eng. 2019, 7, 7304–7311. 10.1021/acssuschemeng.9b00370. [DOI] [Google Scholar]
  53. Temnikov M. N.; Vasil’ev V. G.; Buzin M. I.; Muzafarov A. M. Synthesis and comparison of the rheological and thermal properties of acyclic and polycyclic forms of polyphenylsilsesquioxane. Eur. Polym. J. 2020, 130, 109676. 10.1016/j.eurpolymj.2020.109676. [DOI] [Google Scholar]
  54. Zhang X.; Yu M.; Laine R. M. An Approach to Epoxy Resins: Oxysilylation of Epoxides. Macromolecules 2020, 53, 2249–2263. 10.1021/acs.macromol.9b02676. [DOI] [Google Scholar]
  55. Zhang H.; Xue L.; Li J.; Ma Q. Hyperbranched Polycarbosiloxanes: Synthesis by Piers-Rubinsztajn Reaction and Application as Precursors to Magnetoceramics. Polymers 2020, 12, 672. 10.3390/polym12030672. [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Drozdov F. V.; Milenin S. A.; Gorodov V. V.; Demchenko N. V.; Buzin M. I.; Muzafarov A. M. Crosslinked polymers based on polyborosiloxanes: Synthesis and properties. J. Organomet. Chem. 2019, 891, 72–77. 10.1016/j.jorganchem.2019.04.016. [DOI] [Google Scholar]
  57. Morgan J.; Chen T.; Hayes R.; Dickie T.; Urlich T.; Brook M. A. Facile synthesis of dendron-branched silicone polymers. Polym. Chem. 2017, 8, 2743–2746. 10.1039/c7py00260b. [DOI] [Google Scholar]
  58. Schneider A. F.; Laidley E.; Brook M. A. Facile Synthesis of C-x(AB)(y)C-x Triblock Silicone Copolymers Utilizing Moisture Mediated Living-End Chain Extension. Macromol. Chem. Phys. 2019, 220, 1800575. 10.1002/macp.201800575. [DOI] [Google Scholar]
  59. Chen X.; Yi M.; Wu S.; Tan L.; Ge X.; He M.; Yin G. Synthesis of Structurally Precise Polysiloxanes via the Piers-Rubinsztajn Reaction. Materials 2019, 12, 304. 10.3390/ma12020304. [DOI] [PMC free article] [PubMed] [Google Scholar]
  60. Yi M.; Chen X.; Wu S.; Ge J.; Zhou X.; Yin G. Fabrication of Reactive Poly(Phenyl-Substituted Siloxanes/Silsesquioxanes) with Si-H and Alkoxy Functional Groups via the Piers-Rubinsztajn Reaction. Polymers 2018, 10, 1006. 10.3390/polym10091006. [DOI] [PMC free article] [PubMed] [Google Scholar]
  61. Grande J. B.; Urlich T.; Dickie T.; Brook M. A. Silicone dendrons and dendrimers from orthogonal SiH coupling reactions. Polym. Chem. 2014, 5, 6728–6739. 10.1039/c4py00680a. [DOI] [Google Scholar]
  62. Yu J.; Liu Y. Cyclic Polysiloxanes with Linked Cyclotetrasiloxane Subunits. Angew. Chem., Int. Ed. Engl. 2017, 56, 8706–8710. 10.1002/anie.201703347. [DOI] [PubMed] [Google Scholar]
  63. Parks D. J.; Piers W. E. Tris(pentafluorophenyl)boron-Catalyzed Hydrosilation of Aromatic Aldehydes, Ketones and Esters. J. Am. Chem. Soc. 1996, 118, 9440–9441. 10.1021/ja961536g. [DOI] [Google Scholar]
  64. Schneider A. F.; Brook M. A. High-Throughput Synthesis and Characterization of Aryl Silicones by Using the Piers-Rubinsztajn Reaction. Chem.—Eur. J. 2019, 25, 15367–15374. 10.1002/chem.201903658. [DOI] [PubMed] [Google Scholar]
  65. Schneider A. F.; Chen Y.; Brook M. A. Trace water affects tris(pentafluorophenyl)borane catalytic activity in the Piers-Rubinsztajn reaction. Dalton Trans. 2019, 48, 13599–13606. 10.1039/c9dt02756d. [DOI] [PubMed] [Google Scholar]
  66. Honda S.; Ohkita H.; Benten H.; Ito S. Multi-coloured Dye Sensitization of Polymer/Fullerene Bulk Heterojunction Solar Cells. Chem. Commun. 2010, 46, 6596–6598. 10.1039/c0cc01787f. [DOI] [PubMed] [Google Scholar]
  67. Honda S.; Yokoya S.; Ohkita H.; Benten H.; Ito S. Light-Harvesting Mechanisms in Polymer/Fullerene/Dye Ternary Blends Studied by Transient Absorption Spectroscopy. J. Phys. Chem. C 2011, 115, 11306–11317. 10.1021/jp201742v. [DOI] [Google Scholar]
  68. Hansch C.; Leo A.; Taft R. W. A survey of Hammett substituent constants and resonance and field parameters. Chem. Rev. 1991, 91, 165–195. 10.1021/cr00002a004. [DOI] [Google Scholar]
  69. Lowery M. K.; Starshak A. J.; Esposito J. N.; Krueger P. C.; Kenney M. E. Dichloro(phthalocyanino)silicon. Inorg. Chem. 1965, 4, 128. 10.1021/ic50023a036. [DOI] [Google Scholar]

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