Abstract
In this study, cyanine cations with various counter anions were prepared as examples of ionic materials constructed using charged π-conjugated systems. A series of ion pairs was obtained by anion exchange reactions using iodide salts of carbocyanine dyes. The optical properties were measured by UV/vis absorption and fluorescence spectroscopy; measurements performed in CHCl3 (less-polar solvent) were altered by the influence of the counter anions. The packing structures of nine crystals were determined by single-crystal X-ray analysis. Moreover, the locations of the anions relative to the cations were stabilized by hydrogen bonding and categorized into two types. In addition, delocalization of the negative charge of the anions on cyanine cations was explained by density functional theory calculations. Furthermore, it was concluded that the stack formation of cyanine cations depends on the size and structure of the anions.
Introduction
Ionic materials constructed using charged π-conjugated systems have attracted much attention because of their ability to control the properties by a combination of cations and anions.1−3 By using monovalent ions, cations and anions are crystallized in a 1:1 ratio based on electrostatic interactions, and crystals with high melting point and hardness are provided with the strong Coulomb force. Moreover, the crystal structures and electronic states can be influenced by the location and structure of the counter ions as cations and anions are sufficiently close to each other.4−7 Cyanine cations, one of the polymethines, have recently been studied as photoswitching materials with photoisomerization properties and as near-infrared light-emitting materials with an increased Stokes shift.8−10 A symmetrically N-substituted cyanine cation has a long-conjugated resonance hybrid structure expressed using two asymmetrical resonance forms. However, the electronic state can be asymmetrically modified by varying the location of the counter anion (Figure 1a).11−17 Such asymmetric polar π-electronic states are useful for piezoelectric, pyroelectric, and second-order nonlinear optical materials. In addition, ferroelectricity may be achieved by selectively controlling the positions of counter anions at one of two asymmetric stable positions, such as the upper and lower formulae in Figure 1a, by applying an external electric field. However, there are few reports on the systematic investigations of the effects of counter anions on the assembled structure of cyanine cations.11 Moreover, a sulfonate group is one of the stable anionic substituents, possessing a delocalized negative charge on three oxygens, and can be introduced into π-electronic systems to provide π-electronic anions with large polarity. For example, p-toluenesulfonate tends to form polar crystals with stilbazolium derivatives, and its application to second-order nonlinear materials has been reported.18−20 In this study, cyanine cations with various counter anions, including sulfonate anions, were prepared, and the positional relationship of ion pairs and their assembled structures was revealed by single-crystal X-ray analysis.
Figure 1.
(a) Chemical structures of 1,1′-dialkyl-2,2′-carbocyanine cations (dmcc and decc) and their polar transfer depending on the location of the counter anion (X–) and (b) chemical structures of anions.
Results and Discussion
Iodide salts of carbocyanine cations (dmcc-I and decc-I) were prepared by the condensation reaction of the corresponding 1-alkyl-2-methylquinolinium iodide and triethyl orthoformate in pyridine. Chloride (Cl), p-toluensulfonate (TS), 4-nitrobenzenesulfonate (NS), aminobenzenesulfonate (AS), (+)-10-camphorsulfonate (CS), and 1-pyrenesulfonate (PS) salts of carbocyanine cations were prepared by anion exchange reactions using dmcc-I and decc-I (Figure 1b). Their identifications were performed using 1H and 13C NMR spectra. All ion pairs exhibited high thermal stabilities with thermal decomposition temperatures of >250 °C.
UV/vis absorption and fluorescence spectra in methanol and chloroform were investigated using ethyl-substituted decc salts as the solubility of these derivatives in organic solvents is relatively higher than that of dmcc salts (Figure 2 and Table 1). In methanol (10–5 M), the maxima of UV/vis absorption and fluorescence spectra were observed at 604 and 614 nm, respectively, for all compounds derived from decc, regardless of the counter anion. Thus, the effect of counter anions for the π-electronic systems was not observed in methanol as polar solvent, in which the interaction within an ion pair is weak due to solvation. However, the absorption and fluorescence maxima were slightly altered in a less polar solvent, such as chloroform using different counter anions, and red-shifted from those in methanol. Such bathochromic shifts could be attributed to the effects of solvation and the counter ions both, depending on solvent polarities. The absorption maxima (λmax) of decc-I and decc-Cl were the same (604 nm) in methanol, whereas they were 610 and 614 nm for decc-I and decc-Cl, respectively, in chloroform. This indicates that the contribution of the counter ion to the λmax in chloroform was larger than that in methanol. Furthermore, the solid-state diffuse reflectance spectra were investigated using the ground powder on filter papers. The maximum bands were observed at ca. 615 nm (Figure S17), and the difference in the absorption maxima depending on the counter anion was small (∼3 nm).
Figure 2.
UV/vis absorption (solid line) and fluorescence spectra (dashed line) of decc-I (red) and decc-Cl (blue) in (a) methanol and (b) chloroform (10–5 M).
Table 1. Details of the Absorption and Fluorescence Emission Maxima of decc-I, decc-Cl, decc-TS, decc-NS, decc-AS, decc-CS, and decc-PS in MeOH and CHCl3 (10–5 M)a.
| λabs [nm] (ε 105 L/mol cm) |
λem [nm] |
|||
|---|---|---|---|---|
| in MeOH | in CHCl3 | in MeOH | in CHCl3 | |
| decc-I | 604 (1.8) | 614 (1.4) | 614 | 622 |
| decc-Cl | 604 (1.7) | 610 (1.4) | 613 | 618 |
| decc-TS | 604 (1.7) | 609 (1.5) | 614 | 618 |
| decc-NS | 604 (1.6) | 611 (1.6) | 614 | 622 |
| decc-AS | 604 (1.6) | 609 (1.2) | 614 | 620 |
| decc-CS | 604 (1.9) | 609 (1.4) | 614 | 621 |
| decc-PS | 604 (1.8) | 611 (1.4) | 614 | 621 |
The emission maxima were obtained by excitation at the respective absorption maxima.
All synthesized compounds were screened using several crystallization methods (e.g., slow evaporation, vapor diffusion, and slow cooling), and nine single crystals ([dmcc][I], [decc][I]-i and ii (two pseudopolymorphs), [decc][Cl], [decc][TS], [decc][NS], [decc][AS], [decc][CS], and [decc][PS]) appropriate for X-ray crystallographic analysis were obtained.
First, we compared the crystal structures of the ion pairs, including spherical I and Cl anions. The ion pair of dmcc-I was crystallized in the monoclinic C2/c space group, and the ion pair decc-I gave two pseudopolymorphs including acetonitrile ([decc][I]-i) and methanol ([decc][I]-ii) that crystallized in the orthorhombic Pbcm space group and monoclinic P21/c space group, respectively. The ion pair decc-Cl was crystallized in the monoclinic P21/n space group, and four independent ion pairs and H2O were included. To understand the interaction between the cation and anion, the location of the nearest anion relative to the cation was studied. The location of the anion is categorized into site A, where the anion is stabilized by three hydrogen bonds with the bridged CH and the quinoline CH, and site B, where the anion is stabilized by two hydrogen bonds with bridged CH (Figure 3a). In crystals [dmcc][I] and [decc][I]-i, the anions are coplanar with cations and stabilized at site A (Figure 4a,b) with C(−H)···I average distances of 4.20 and 4.10 Å, respectively. Especially in [decc][I]-i, one of the two independent anions is stabilized by two decc cations, both at site A, to form an in-plane dimer and the other anion exists in a free state without interaction with the cation (Figure S19). On the other hand, in crystal [decc][I]-ii, the anion is located at site B (Figure 4c) with a C(−H)···I average distance of 4.14 Å. Thus, the aggregation form depends on the solvent molecules included. In crystal [decc][Cl], four independent structures were observed and one of four Cl anions (Cl1) is located at site A with a C(−H)···Cl average distance of 3.72 Å. On the other hand, another Cl anion (Cl2) located at sites A and B of two cations with C(−H)···Cl average distances of 3.93 and 3.75 Å, respectively (Figure 4d), stabilized the stacking formation. The other two Cl anions have only a partial interaction between the anions and cyanine, and the hydrogen bonding network was constructed by Cl anions and water molecules.
Figure 3.
(a) Schematic illustration for the two kinds of anion-located sites of the cyanine cation; (b) definitions of the stacking distance (d) and the longitudinal offset (L) of the cation dimers.
Figure 4.
Single-crystal X-ray structures of (a) [dmcc][I], (b) [decc][I]-i, (c) [decc][I]-ii, and (d) [decc][Cl]: (i) stick representations of ion pairs and (ii) space filling models of stacking dimers (top and side views). Atom color code: gray, blue, purple, green, and pink refer to carbon, nitrogen, iodide, chloride, and hydrogen, respectively.
In the stacking structures of cations, a dimerized structure with the same (syn-) directional stacking was obtained in [decc][I]-i, where the dipole moments along the short axes of cations strengthened each other [Figure 4b(ii)]. In contrast, opposite (anti-) directional stacking was observed in [dmcc][I] and [decc][I]-ii, which resulted in the dipole moments canceling each other [Figure 4a,c(ii)]. The stacking distances (d) and the longitudinal offsets (L) of the cation dimers, defined in Figure 3b, were 3.53 and 0.9 Å for [dmcc][I], 3.47 and 4.3 Å for [decc][I]-i, and 3.52 and 1.6 Å for [decc][I]-ii, respectively. On the other hand, in [decc][Cl], two kinds of anti-directional stacking dimers were obtained, and d and L were 3.51/3.60 and 0.8/<0.1 Å, respectively. Thus, similar stacking distances were observed, regardless of the counter anions and the stacking conformation, whereas the longitudinal offsets of the syn-type dimer tended to be smaller than those of the anti-type dimer. These results indicate that the dipole–dipole interactions stabilize the dimeric forms of the anti-type dimer. Moreover, the stacking structures of the cations were observed in [dmcc][I], [decc][I]-i, and [decc][I]-ii. In [dmcc][I], a stacking structure was constructed using a sequence of cation dimers. On the other hand, in [decc][I]-i and [decc][I]-ii, the columnar structures along the a axis were constructed by the syn- and anti-type stacking of decc, respectively, and decc in [decc][I]-i formed a herringbone structure.
The crystal structures of the ion pairs with anisotropic sulfonate derivatives were studied (Figure 5). Ion pair of decc-NS was crystallized in the triclinic P1̅ space group, decc-PS was crystallized in the monoclinic P21/n, and decc-TS and decc-AS were crystallized in the monoclinic P21/c space group. The decc-CS ion pair using a chiral anion was crystallized in the monoclinic P21 space group. The anti-directional stacking of cations was observed in all the sulfonate ion pairs. Focusing on the interaction between cations and anions, location of one of the three oxygen atoms of the sulfonates is coplanar with the cyanine cation plane with C–H···O hydrogen bonding at sites A and B (Figure 5). In particular, a one-dimensional hydrogen bonding network is formed via sites A and B in [decc][PS] (Figure S26). In addition, the least-squares planes of the cations and aromatic groups of the counter anions are nearly orthogonal (85–92°) because of the C–S–O angles (103.9–106.7°) in the sulfonate derivatives. Therefore, π–π interactions between cations and anions can be ignored.
Figure 5.
Single-crystal X-ray structures of (a) [decc][TS], (b) [decc][NS], (c) [decc][AS], (d) [decc][CS], and (e) [decc][PS]: (i) stick representations of ion pairs (top and side views), (ii) space filling models of dimers (top and side views), and (iii) packing diagrams (views along the a, b, and c axes) of ion pairs, wherein the magenta- and cyan-colored parts represent the anion and cation species, respectively. The atom color code for (i) and (ii) is as follows: gray, blue, red, and pink refer to carbon, nitrogen, oxygen, and hydrogen, respectively.
In all ion pairs of decc with sulfonate derivatives, decc constructed anti-directional stacking dimers. The stacking distances (d) and the longitudinal offsets (L) of cation dimers were 3.38 and 5.3 Å for [decc][TS], 3.44 and 1.3 Å for [decc][NS], 3.65 and 2.8 Å for [decc][AS], and 3.52 and 7.3 Å for [decc][PS]. These results indicate that the longitudinal offset increases when the long axis of the anion approaches parallel to the long axis of the cation, as in the cases of [decc][TS] and [decc][PS]. However, cyanine cations formed an identical anti-directional dimer in [decc][CS] constructed with a bulky sulfonate, which is stabilized by the two hydrogen-bonded bridges via one sulfonate. The stacking distance (d) and the longitudinal offset (L) were 3.73 and 0.8 Å, respectively. It should be noted that the packing structure of [decc][TS] exhibits a charge-segregated assembly, wherein both positively and negatively charged components form layered structures of identically charged species [Figure 5a(iii)]. The cations in [decc][TS] are packed in a herringbone structure along the a axis, whereas the TS forms a sheet-like structure parallel to the (110) plane. Furthermore, the intermolecular N–H···O hydrogen bonding between ASs [N(−H)···O = 3.00 Å] provided a two-dimensional undulated network parallel to the (110) plane in [decc][AS] [Figure 5c(iii)]. Thus, cation-to-cation stacking was observed in all crystals, whereas anion-to-anion stacking was not observed because of the electron-rich character of the π-electronic system bearing anionic substituents and relatively smaller π-planes.
To discuss the effect of the variety and location of counter anions on the polarization of cyanine cations, the bond length alternation (BLA) was estimated (Figure S28). As shown in Table 2, all crystal structures gave small BLA values (∼0.021), indicating the symmetrical delocalization of the positive charge on the cyanine cations. These results can be explained by the location of the counter anion, which is near the center line of the cyanine cations, regardless of site A or B. The relatively large BLA in [decc][CS] may be a result of the noncentrosymmetric structure of [decc][CS].
Table 2. Structural Data and Calculated Properties of [dmcc][I], [decc][I]-i, [decc][I]-ii, [decc][Cl], [decc][TS], [decc][NS], [decc][AS], [decc][CS], and [decc][PS].
| [dmcc][I] | [decc][I]-i | [decc][I]-ii | [decc][Cl] | [decc][TS] | [decc][NS] | [decc][AS] | [decc][CS] | [decc][PS] | |
|---|---|---|---|---|---|---|---|---|---|
| solvate | MeCN | MeOH | H2O | ||||||
| coordination site | A | A (dimer) | B | A/B | A/B | A | A | A/B | A/B |
| BLA | 0.006 | 0.013 | 0.006–0.014 | 0, 0.004 | 0.011 | 0.007 | 0.021, 0.015 | 0.008 | |
| stacking typea | D | H | P | D | H | P | P | D | P |
P, H, and D implying the columnar parallel structure, columnar herringborn-type structure, and dimer structure, respectively (see Figure S27).
We calculated the electrostatic potential (ESP) mapping of the cyanine cation and sulfonate derivatives (Figure 6). In decc, the positive charge at sites A and B was slightly larger than that on the other parts, although the positive charge was delocalized on the π-electronic systems. This result is consistent with the crystal structures, in which most anions formed hydrogen bonding at sites A or B. Moreover, the ESP mapping for ion pairs was estimated from the crystal structures of [decc][I]-i, [decc][I]-ii, [decc][NS], and [decc][AS], and the delocalization of the negative charge of the anion on the cyanine cation through hydrogen bonding was observed, regardless of the location and the type of anions (Figure 6b). The effect of anions at sites A and B was compared with decc-I in [decc][I]-i and [decc][I]-ii, and more efficient delocalization of the negative charge on the cyanine cation was found in [decc][I]-i, wherein the anion was located at site A. By comparing [decc][NS] and [decc][AS], the negative charge on SO3– was determined to be relatively smaller in the NS with electron withdrawing substituents, and consequently, the electron density on decc was also lower.
Figure 6.
(a) ESPs mapped on the electron density isosurfaces (δ = 0.01) calculated for the optimized structure of decc, (i) top view and (ii) side views from two directions and (b) ESP mapped on the electron density isosurfaces (δ = 0.005) (top and side views) calculated as ion pairs for (i) [decc][I]-i, (ii) [decc][I]-ii, (iii) [decc][NS], and (iv) [decc][AS] from the single-crystal X-ray structures. The calculation was performed at B3LYP/6-31G(d,p) for H, C, N, and O and B3LYP/LANL2DZ for I.
Conclusions
Several ion pairs based on 1,1′-dialkyl-2,2′-carbocyanine cations were prepared by ion exchange using iodide salts of 1,1′-dialkyl-2,2′-carbocyanine cations. The absorption and fluorescence spectra in polar solvents such as methanol were not changed, regardless of the type of the counter anions. However, the spectra were altered due to the influence of the counter anion in a less polar solvent such as chloroform. Nine ionic crystals were obtained, and the assembled structures were revealed by single-crystal X-ray analysis. In all ionic crystals, the anions were stabilized via hydrogen bonding with the cyanine cations, and their locations could be categorized into two sites near the center of the cyanine cations. In the ion pairs, the delocalization of the negative charge of anions on cyanine cations was observed by density functional theory calculations. In the packing structures, syn- or anti-type cation–cation stack formations were observed for all crystals. There was no change in the distances between the cations; however, the offset distances were controlled by the type of stacking or the size of the anions. Moreover, a charge-segregated assembly was obtained. Among nine crystal structures, eight were centrosymmetric and one polar structure was obtained only for the ion pair with a chiral anion. To break the centrosymmetry of this series of ion pair crystals, a larger deviation of the anion positions from the center of cyanine cations is necessary. Future work could involve elongation of the π-conjugated bridge between heterocyclic rings and the introduction of bulky N-alkyl groups. Thus, we demonstrated the potential of the 1,1′-dialkyl-2,2′-carbocyanine cation as a component for the fascinating ionic crystals. Furthermore, the research on determination of novel ionic crystals and their applications in organic materials, including NLO materials, ferroelectric materials, and solar cell devices, is ongoing in our laboratory.
Experimental Section
General Information
Starting materials were purchased from Kanto Chemical, TCI, and Sigma-Aldrich and used without further purification unless otherwise stated. 1H and 13C nuclear magnetic resonance (NMR) spectroscopies were investigated on JEOL ECX-400 400 MHz and JEOL ECZ-600 600 MHz spectrometers using DMSO-d6 (δ 2.50 and 39.5 for 1H and 13C NMR, respectively) as the internal standards. UV–vis absorption and diffuse reflectance spectra were recorded on a JASCO V-570 spectrometer. Fluorescence spectra were recorded on a JASCO FP-8600 fluorescence spectrometer.
Synthesis
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine Iodide, dmcc-I
A mixture of 1,2-dimethylquinolinium iodide (0.982 g and 3.44 mmol) and triethyl orthoformate (1.02 g and 6.88 mmol) in dry pyridine (15 mL) was refluxed overnight. The reaction mixture was cooled to r.t., and dmcc-I was obtained as a blue precipitate (0.815 g, quant). M.p.: 273 °C. 1H NMR (400 MHz, DMSO-d6, δ): 3.92 (6H, s), 6.53 (2H, d, J = 12.7 Hz), 7.46 (2H, dd, J = 7.7, 6.8 Hz), 7.75 (2H, dd, J = 8.2, 6.8 Hz), 7.84 (2H, d, J = 7.7 Hz), 7.89 (2H, d, J = 8.2 Hz), 8.01 (2H, d, J = 9.5 Hz), 8.28 (2H, d, J = 9.5 Hz), 8.66 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 36.11, 106.14, 116.39, 119.82, 124.38, 124.78, 128.81, 132.18, 135.42, 139.60, 146.61, 153.05.
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine Chloride, dmcc-Cl
A column containing Amberlite resin (Amberlite IRA400J Cl) was thoroughly washed with 1 M HCl aq. A solution of dmcc-I (300 mg and 0.663 mmol) in acetone and water was slowly added from the top of the column and passed through. After removing the solvent from the eluent, the residue was recrystallized from a mixture of acetone and MeOH to afford dmcc-Cl (200 mg, 0.615 mmol, and 93%) as a black powder. M.p.: 258 °C. 1H NMR (400 MHz, DMSO-d6, δ): 3.89 (6H, s), 6.50 (2H, d, J = 13.1 Hz), 7.42 (2H, dd, J = 7.7, 7.1 Hz), 7.71 (2H, dd, J = 9.1, 7.1 Hz), 7.81 (2H, d, J = 7.7 Hz), 7.86 (2H, d, J = 9.1 Hz), 7.99 (2H, d, J = 9.5 Hz), 8.28 (2H, d, J = 9.5 Hz), 8.64 (1H, t, J = 13.1 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 36.14, 106.21, 116.43, 119.90, 124.41, 124.79, 128.85, 132.18, 135.42, 139.60, 146.63, 153.01.
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine p-Toluenesulfonate, dmcc-TS
A solution of silver p-toluenesulfonate (0.148 g and 0.530 mmol) in methanol (20 mL) was added to dmcc-I (0.240 g and 0.530 mmol) in methanol (50 mL), and the mixture was stirred overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salt were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford dmcc-TS (0.177 g, 0.356 mmol, and 67%) as a green powder. M.p.: 288 °C. 1H NMR (400 MHz, DMSO-d6, δ): 2.28 (3H, s), 3.90 (6H, s), 6.50 (2H, d, J = 12.7 Hz), 7.10 (2H, d, J = 8.4 Hz), 7.43 (2H, dd, J = 7.7, 6.8 Hz), 7.48 (2H, d, J = 8.4 Hz), 7.72 (2H, ddd, J = 9.1, 6.8, 1.3 Hz), 7.81 (2H, dd, J = 7.7, 1.3 Hz), 7.86 (2H, d, J = 9.1 Hz), 7.99 (2H, d, J = 9.5 Hz), 8.27 (2H, d, J = 9.5 Hz), 8.63 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 20.61, 36.04, 106.11, 116.33, 119.78, 124.34, 124.70, 125.39, 127.83, 128.75, 132.09, 135.35, 137.30, 139.54, 145.91, 146.54, 152.97.
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine 4-Nitrobenzenesulfonate, dmcc-NS
A solution of silver 4-nitrobenzenesulfonate (69.8 mg and 0.225 mmol) in methanol (20 mL) was added to dmcc-I (102 mg and 0.225 mmol) in methanol (100 mL), and the mixture was stirred overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford dmcc-NS (84.0 mg, 0.159 mmol, and 71%) as a green powder. M.p.: 292 °C. 1H NMR (400 MHz, DMSO-d6, δ): 3.91 (6H, s), 6.51 (2H, d, J = 12.7 Hz), 7.44 (2H, dd, J = 7.7, 7.3 Hz), 7.73 (2H, ddd, J = 8.6, 7.3, 1.6 Hz), 7.80–7.86 (4H, m) 7.87 (2H, d, J = 8.6 Hz), 7.99 (2H, d, J = 9.5 Hz), 8.18 (2H, d, J = 9.1 Hz), 8.26 (2H, d, J = 9.5 Hz) 8.64 (1H, t, J = 12.7 Hz). 13C NMR (150 MHz, DMSO-d6, δ): 36.04, 106.09, 116.33, 119.78, 123.11, 124.34, 124.71, 126.78, 128.76, 132.11, 135.35, 139.55, 146.55, 147.13, 152.99, 154.40.
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine Sulfanilate, dmcc-AS
The solution of silver sulfanilate (36.4 mg and 0.130 mmol) in water (20 mL) was added to dmcc-I (58.7 mg and 0.130 mmol) in methanol (80 mL), and the mixture was stirred overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford dmcc-AS (55.0 mg, 0.111 mmol, and 85%) as a green powder. M.p.: 301 °C. 1H NMR (400 MHz, DMSO-d6, δ): 3.92 (6H, s), 5.11 (2H, br s), 6.43 (2H, d, J = 8.3 Hz), 6.53 (2H, d, J = 13.1 Hz), 7.24 (2H, d, J = 8.3 Hz), 7.46 (2H, dd, J = 8.2, 6.6 Hz), 7.75 (2H, ddd, J = 8.6, 6.6, 1.4 Hz), 7.84 (2H, dd, J = 8.2, 1.4 Hz), 7.90 (2H, d, J = 8.6 Hz), 8.01 (2H, d, J = 9.5 Hz), 8.29 (2H, d, J = 9.5 Hz), 8.67 (1H, t, J = 13.1 Hz). 13C NMR (150 MHz, DMSO-d6, δ): 36.06, 106.11, 112.13, 116.37, 119.80, 124.36, 124.74, 126.49, 128.78, 132.14, 135.38, 136.68, 139.58, 146.59, 148.45, 153.03.
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine (+)-10-Camphorsulfonate, dmcc-CS
The solution of dmcc-I (85.3 mg and 0.189 mmol) and silver oxide (21.9 mg and 0.0945 mmol) in methanol (50 mL) was stirred 5 h at 0 °C. After removing the precipitates, (+)-10-camphorsulfonic acid monohydrate (43.9 mg and 0.189 mmol) was added to the reaction mixture, and it was stirred overnight at r.t. The solution was concentrated, and the precipitates produced by adding Et2O were collected by filtration to obtain dmcc-CS (72.0 mg, 0.129 mmol, and 69%) as a green powder. M.p.: 284 °C. 1H NMR (400 MHz, DMSO-d6, δ): 0.74 (3H, s), 1.06 (3H, s) 1.21–1.32 (2H, m), 1.78 (1H, d, J = 18.1 Hz), 1.85 (1H, m) 1.93 (1H, dd, J = 4.6, 4.6 Hz), 2.23 (1H, ddd, J = 18.1, 4.6, 3.5 Hz), 2.37 (1H, d, J = 14.9 Hz), 2.72 (1H, m), 2.87 (1H, d, J = 14.9 Hz), 3.91 (6H, s), 6.51 (2H, d, J = 12.7 Hz), 7.43 (2H, dd, J = 7.7, 7.3 Hz), 7.72 (2H, ddd, J = 8.6, 7.3, 1.4 Hz), 7.81 (2H, dd, J = 7.7, 1.4 Hz), 7.87 (2H, d, J = 8.6 Hz), 7.99 (2H, d, J = 9.5 Hz), 8.27 (2H, d, J = 9.5 Hz), 8.64 (1H, t, J = 12.7 Hz). 13C NMR (150 MHz, DMSO-d6, δ): 19.43, 20.06, 24.09, 26.29, 36.03, 42.14, 42.17, 46.61, 46.82, 58.21, 106.07, 116.29, 119.77, 124.33, 124.69, 128.74, 132.09, 135.35, 139.55, 146.54, 153.01, 216.15.
Preparation of 1,1′-Dimethyl-2,2′-carbocyanine 1-Pyrenesulfonate, dmcc-PS
A solution of silver 1-pyrenesulfonate (0.100 g and 0.257 mmol) in water (50 mL) was added to dmcc-I (0.116 g and 0.257 mmol) in methanol (100 mL), and the mixture was stirred overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford dmcc-PS (55.0 mg, 0.111 mmol, and 85%) as a green powder. M.p.: >280 °C. 1H NMR (400 MHz, DMSO-d6, δ): 3.88 (6H, s), 6.48 (2H, d, J = 12.7 Hz), 7.42 (2H, dd, J = 7.7, 7.1 Hz), 7.71 (2H, dd, J = 8.6, 7.1 Hz), 7.78 (2H, d, J = 7.7 Hz), 7.84 (2H, d, J = 8.6 Hz), 7.96 (2H, d, J = 9.5 Hz), 8.06 (1H, dd, J = 7.7, 7.7 Hz), 8.12–8.21 (4H, m), 8.24 (2H, d, J = 9.5 Hz), 8.26–8.31 (2H, m), 8.52 (1H, d, J = 8.0 Hz), 8.61 (1H, t, J = 12.7 Hz), 9.20 (1H, d, J = 9.5 Hz). 13C NMR (150 MHz, DMSO-d6, δ): 36.02, 106.08, 116.30, 119.77, 123.58, 123.64, 124.11, 124.32, 124.69, 124.73, 125.08, 125.11, 126.04, 126.46, 126.77, 126.83, 127.15, 127.44, 128.74, 130.04, 130.59, 131.08, 132.08, 135.32, 139.53, 142.10, 146.51, 152.95.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine Iodide, decc-I
A mixture of 1-ethyl-2-methylquinolinium iodide (0.899 g and 3.01 mmol) and triethyl orthoformate (0.892 g and 6.02 mmol) in dry pyridine (14 mL) was refluxed overnight. The reaction mixture was cooled to r.t., and decc-I was obtained as a blue precipitate (0.707 g, 1.47 mmol, and 98%). M.p.: 271 °C. 1H NMR (400 MHz, DMSO-d6, δ): 1.43 (6H, t, J = 7.2 Hz), 4.47 (4H, br m), 6.58 (2H, d, J = 12.7 Hz), 7.45 (2H, dd, J = 7.7, 7.3 Hz), 7.74 (2H, ddd, J = 8.6, 7.3, 1.4 Hz), 7.83 (2H, dd, J = 7.7, 1.4 Hz), 7.87 (2H, d, J = 8.6 Hz), 8.00 (2H, d, J = 9.8 Hz), 8.30 (2H, d, J = 9.8 Hz), 8.70 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.47, 42.83, 105.34, 115.97, 119.97, 124.60, 124.77, 129.06, 132.38, 135.48, 138.47, 147.33, 151.84.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine Chloride, decc-Cl
A column containing Amberlite resin (IRA400J Cl) was thoroughly washed with 1 M HCl aq. A solution of decc-I (49.9 mg and 0.104 mmol) in acetone and water was slowly added from the top of the column and passed through. After removing the solvent from the eluent, the residue was recrystallized from acetone and MeOH to afford decc-Cl (39.0 mg, 0.100 mmol, and 98%) as a black powder. M.p.: 265 °C. 1H NMR (400 MHz, DMSO-d6, δ): 1.43 (6H, t, J = 7.2 Hz), 4.47 (4H, br m), 6.57 (2H, d, J = 12.7 Hz), 7.43 (2H, dd, J = 7.7, 6.9 Hz), 7.73 (2H, dd, J = 8.6, 6.9 Hz), 7.83 (2H, d, J = 7.7 Hz), 7.86 (2H, d, J = 8.6 Hz), 7.98 (2H, d, J = 9.5 Hz), 8.32 (2H, d, J = 9.5 Hz), 8.70 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.42, 42.79, 105.36, 115.97, 120.03, 124.60, 124.76, 129.04, 132.35, 135.46, 138.46, 147.45, 151.87.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine p-Toluenesulfonate, decc-TS
A solution of silver p-toluenesulfonate (53.6 mg and 0.192 mmol) in methanol (30 mL) was added to decc-I (0.092 g and 0.192 mmol) in methanol (100 mL), and the mixture was stirred overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford decc-TS (83.0 mg, 0.158 mmol, and 82%) as a green powder. M.p.: 300 °C. 1H NMR (400 MHz, DMSO-d6, δ): 1.43 (6H, t, J = 6.8 Hz), 2.28 (3H, s), 4.46 (4H, br m), 6.56 (2H, d, J = 12.7 Hz), 7.11 (2H, d, J = 8.0 Hz), 7.44 (2H, dd, J = 7.7, 7.1 Hz), 7.49 (2H, d, J = 8.0 Hz), 7.74 (2H, ddd, J = 8.6, 7.1, 1.4 Hz), 7.82 (2H, d, J = 7.7 Hz), 7.86 (2H, d, J = 8.6 Hz), 7.98 (2H, d, J = 9.5 Hz), 8.28 (2H, d, J = 9.5 Hz), 8.68 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.44, 20.74, 42.82, 105.34, 116.01, 119.99, 124.63, 124.83, 125.48, 128.00, 129.09, 132.43, 135.53, 137.53, 138.50, 146.38, 147.42, 151.91.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine 4-Nitrobenzenesulfonate, decc-NS
A solution of silver 4-nitrobenzenesulfonate (37.5 mg and 0.121 mmol) in water (20 mL) was added to decc-I (58.0 mg and 0.121 mmol) in methanol (120 mL), and the mixture was stirred overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford decc-NS (56.0 mg, 0.101 mmol, and 83%) as a green powder. M.p.: 267 °C. 1H NMR (400 MHz, DMSO-d6, δ): 1.44 (6H, t, J = 7.2 Hz), 4.48 (4H, br m), 6.57 (2H, d, J = 12.7 Hz), 7.46 (2H, dd, J = 7.9, 6.5 Hz), 7.76 (2H, dd, J = 8.7, 6.5 Hz), 7.84 (2H, d, J = 8.9 Hz), 7.84 (2H, d, J = 7.9 Hz), 7.88 (2H, d, J = 8.7 Hz), 8.00 (2H, d, J = 9.5 Hz), 8.19 (2H, d, J = 8.9 Hz), 8.30 (2H, d, J = 9.5 Hz), 8.71 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.42, 42.82, 105.34, 116.02, 119.99, 123.26, 124.64, 124.84, 126.87, 129.09, 132.44, 135.53, 138.51, 147.45, 148.53, 151.93, 154.35.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine Sulfanilate, decc-AS
A solution of silver sulfanilate (60.0 mg and 0.214 mmol) in water (30 mL) was added to decc-I (0.103 g and 0.214 mmol) in methanol (80 mL), and the mixture was heated at 80 °C for 2 h followed by stirring overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford decc-AS (94.1 mg, 0.179 mmol, and 84%) as a green powder. M.p.: 280 °C. 1H NMR (400 MHz, DMSO-d6, δ): 1.43 (6H, t, J = 6.8 Hz), 4.47 (4H, br m) 5.12 (2H, s), 6.44 (2H, dd, J = 8.2, 1.4 Hz), 6.57 (2H, d, J = 12.6 Hz), 7.25 (2H, dd, J = 8.2, 1.4 Hz), 7.45 (2H, dd, J = 7.7, 7.3 Hz), 7.75 (2H, dd, J = 8.6, 7.3 Hz), 7.84 (2H, d, J = 7.7 Hz), 7.87 (2H, d, J = 8.6 Hz), 7.99 (2H, d, J = 9.3 Hz), 8.30 (2H, d, J = 9.3 Hz), 8.70 (1H, t, J = 12.6 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.42, 42.81, 105.34, 112.20, 116.01, 119.99, 122.63, 124.63, 124.83, 126.59, 129.09, 132.42, 135.52, 138.50, 146.38, 147.42, 151.92.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine (+)-10-Camphorsulfonate, decc-CS
A solution of decc-I (51.9 mg and 0.108 mmol) and silver oxide (12.5 mg and 0.0540 mmol) in methanol (35 mL) and water (35 mL) was stirred for 5 h at 0 °C. After removing the precipitates, (+)-10-camphorsulfonic acid monohydrate (25.1 mg and 0.108 mmol) was added to the reaction mixture, and it was stirred overnight at r.t. The solution was concentrated, and the precipitates produced by adding Et2O were collected by filtration to obtain decc-CS (42.0 mg, 0.0718 mmol, and 66%) as a green powder. M.p.: 277 °C. 1H NMR (400 MHz, DMSO-d6, δ): 0.74 (3H, s), 1.05 (3H, s), 1.21–1.30 (2H, m), 1.44 (6H, t, J = 7.2 Hz), 1.78 (1H, d, J = 18.0 Hz), 1.86 (1H, m) 1.92 (1H, d, J = 4.6, 4.6 Hz), 2.23 (1H, ddd, J = 18.1, 4.7, 3.6 Hz), 2.36 (1H, d, J = 14.5 Hz), 2.71 (1H, m), 2.86 (1H, d, J = 14.5 Hz), 4.48 (4H, br m), 6.57 (2H, d, J = 12.7 Hz), 7.46 (2H, dd, J = 7.7, 7.1 Hz), 7.76 (2H, ddd, J = 8.6, 7.1, 1.4 Hz), 7.84 (2H, dd, J = 7.7, 1.4 Hz), 7.88 (2H, d, J = 8.6 Hz), 8.00 (2H, d, J = 9.5 Hz), 8.30 (2H, d, J = 9.5 Hz), 8.71 (1H, t, J = 12.7 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.49, 19.60, 20.23, 24.15, 26.43, 42.16, 42.29, 42.87, 46.66, 47.06, 58.30, 105.39, 116.08, 120.05, 124.69, 124.90, 129.14, 132.49, 135.59, 138.55, 147.50, 151.96, 216.47.
Preparation of 1,1′-Diethyl-2,2′-carbocyanine 1-Pyrenesulfonate, decc-PS
A solution of silver 1-pyrenesulfonate (0.100 g and 0.257 mmol) in water (70 mL) was added to decc-I (0.123 g and 0.257 mmol) in methanol (50 mL), and the mixture was heated at 80 °C for 2 h followed by stirring overnight at r.t. The reaction mixture was filtered through a pad of Celite with methanol as eluent, and the inorganic salts were removed. After removing the solvent from the filtrate, the residue was recrystallized from MeOH to afford decc-PS (0.153 g, 0.241 mmol, and 94%) as a green powder. M.p.: 288 °C. 1H NMR (400 MHz, DMSO-d6, δ): 1.41 (6H, t, J = 7.2 Hz), 4.44 (4H, br m), 6.53 (2H, d, J = 12.7 Hz), 7.42 (2H, dd, J = 7.7, 7.2 Hz), 7.72 (2H, ddd, J = 8.6, 7.2, 1.4 Hz), 7.80 (2H, dd, J = 7.7, 1.4 Hz), 7.83 (2H, d, J = 8.6 Hz), 7.95 (2H, d, J = 9.5 Hz), 8.06 (1H, dd, J = 7.7, 7.7 Hz), 8.12–8.22 (4H, m), 8.26 (2H, d, J = 9.5 Hz), 8.27–8.31 (2H, m), 8.53 (1H, d, J = 8.2 Hz), 8.66 (1H, t, J = 12.7 Hz), 9.20 (1H, d, J = 9.3 Hz). 13C NMR (100 MHz, DMSO-d6, δ): 12.42, 42.81, 105.31, 115.95, 119.96, 123.73*, 124.21, 124.60, 124.78*, 125.28*, 126.21, 126.68, 126.85*, 127.27, 127.64, 129.07, 130.12, 130.69, 131.25, 132.39, 135.46, 138.47, 141.96, 147.36, 151.86. Asterisks indicate overlapped peaks.
X-ray Crystallography
The crystallographic data for the ion pairs are summarized in Table 3. A single crystal of dmcc-I ([dmcc][I]) was obtained by the slow evaporation of the methanol solution. Single crystals of decc-I ([decc][I]-i) and decc-PS ([decc][PS]) were obtained by the slow evaporation of the acetonitrile solutions. Single crystals of decc-I ([decc][I]-ii) were obtained by the slow evaporation of the methanol solution. Single crystals of decc-Cl ([decc][Cl]) and decc-NS ([decc][NS]) were obtained by the vapor diffusion of acetone into the methanol solutions. A single crystal of decc-TS ([decc][TS]) was obtained by the vapor diffusion of acetone into the ethanol solution. A single crystal of decc-AS ([decc][AS]) was obtained by the vapor diffusion of ether into the acetone solution. A single crystal of decc-CS ([decc][CS]) was obtained by the vapor diffusion of acetone into the acetonitrile solution. The data for [dmcc][I], [decc][I]-ii, [decc][Cl], and [decc][PS] were collected at r.t. on a Rigaku RAPID-II diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71075 Å). The data for [decc][TS] and [decc][AS] were collected at 90 K on a Rigaku Saturn724 diffractometer with graphite-monochromated synchrotron radiation (λ = 0.78228 Å). The data for [decc][I]-i and [decc][NS] were collected at 90 K on DECTRIS EIGER with monochromated synchrotron radiation (λ = 0.78255 and 0.78192 Å) at BL40XU (SPring-8),21,22 and the data for [decc][CS] were collected at 100 K on Rigaku PILATUS3 with Si(111)-monochromated synchrotron radiation (λ = 0.4299 Å) at BL02B1 (SPring-8). The structures were refined by a full-matrix least-squares method by using SHELXL 201423 (Yadokari-XG).24 In each structure, the non-hydrogen atoms were refined anisotropically. In this paper, the π-plane distances out of parallel orientations have been defined as the average lengths between non-hydrogen atoms of π units and the mean planes of their neighboring π units. The CIF files (CCDC-2107030–2107038) can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Table 3. Crystallographic Details for [dmcc][I], [decc][I]-i, [decc][I]-ii, [decc][Cl], [decc][TS], [decc][NS], [decc][AS], [decc][CS], and [decc][PS].
| [dmcc][I] | [decc][I]-i | [decc][I]-ii | [decc][Cl] | |
|---|---|---|---|---|
| formula | C23H21N2I | C25H25N2I·0.5CH3CN | C25H25N2I·CH3OH | C25H25N2Cl·H2O |
| fw | 452.32 | 500.90 | 512.41 | 404.92 |
| crystal size, mm | 0.28 × 0.25 × 0.10 | 0.060 × 0.0005 × 0.0005 | 0.41 × 0.10 × 0.08 | 0.68 × 0.35 × 0.19 |
| crystal system | monoclinic | orthorhombic | monoclinic | monoclinic |
| space group | C2/c (no. 15) | Pbcm (no. 57) | P21/c (no. 14) | P21/n (no. 14) |
| a, Å | 17.8673(7) | 5.5329(2) | 7.7512(5) | 17.6674(2) |
| b, Å | 12.4033(4) | 23.3656(7) | 35.350(2) | 20.4329(3) |
| c, Å | 18.5217(7) | 33.5452(12) | 17.2582(14) | 24.7550(3) |
| α, deg | 90 | 90 | 90 | 90 |
| β, deg | 109.5131(9) | 90 | 101.3040(19) | 108.276(2) |
| γ, deg | 90 | 90 | 90 | 90 |
| V, Å3 | 3868.9(2) | 4336.7(3) | 4637.1(6) | 5422(2) |
| ρcalcd, g cm–3 | 1.553 | 1.302 | 1.422 | 1.268 |
| Z | 8 | 8 | 8 | 16 |
| T, K | 299(2) | 90(2) | 300(2) | 302(2) |
| μ, mm–1 | 1.664 (Mo Kα) | 1.907 (synchrotron) | 1.398 (Mo Kα) | 0.199 (Mo Kα) |
| no. of reflns | 18 488 | 21 871 | 66 690 | 128 521 |
| no. of unique reflns | 4397 | 3964 | 10 591 | 24 327 |
| variables | 237 | 276 | 569 | 1129 |
| λ, Å | 0.71075 (Mo Kα) | 0.78255 (synchrotron) | 0.71075 (Mo Kα) | 0.71075 (Mo Kα) |
| R1 [I > 2σ(I)] | 0.0291 | 0.0313 | 0.0663 | 0.0449 |
| wR2 [I > 2σ(I)] | 0.0693 | 0.0667 | 0.1320 | 0.1213 |
| GOF | 1.108 | 1.045 | 1.016 | 1.099 |
| [decc][TS] | [decc][NS] | [decc][AS] | [decc][CS] | |
|---|---|---|---|---|
| formula | C32H32N2O3S | C31H29N3O5S | C31H31N3O3S | C35H40N2O4S |
| fw | 524.65 | 555.63 | 525.65 | 584.75 |
| crystal size, mm | 0.080 × 0.010 × 0.010 | 0.200 × 0.020 × 0.010 | 0.030 × 0.010 × 0.010 | 0.100 × 0.080 × 0.070 |
| crystal system | monoclinic | triclinic | monoclinic | monoclinic |
| space group | P21/c (no. 14) | P1̅ (no. 2) | P21/c (no. 14) | P21 (no. 4) |
| a, Å | 12.5134(6) | 6.9225(4) | 8.4283(3) | 10.484(3) |
| b, Å | 20.2976(11) | 12.6080(7) | 12.7194(4) | 23.392(6) |
| c, Å | 20.5065(7) | 15.2450(7) | 24.0128(8) | 13.186(3) |
| α, deg | 90 | 77.178(4) | 90 | 90 |
| β, deg | 90.120(3) | 88.607(4) | 93.708(3) | 105.978(7) |
| γ, deg | 90 | 89.549(4) | 90 | 90 |
| V, Å3 | 5208.5(4) | 1297.00(12) | 2568.85(15) | 3109.0(13) |
| ρcalcd, g cm–3 | 1.338 | 1.423 | 1.359 | 1.249 |
| Z | 8 | 2 | 4 | 4 |
| T, K | 90(2) | 90(2) | 90(2) | 100(2) |
| μ, mm–1 | 0.162 (synchrotron) | 0.174 (synchrotron) | 0.166 (synchrotron) | 0.051 (synchrotron) |
| no. of reflns | 28 220 | 10 876 | 13 798 | 67 796 |
| no. of unique reflns | 9142 | 4637 | 4646 | 13 930 |
| variables | 691 | 363 | 345 | 781 |
| λ, Å | 0.78228 (synchrotron) | 0.78192 (synchrotron) | 0.78228 (synchrotron) | 0.4299 (synchrotron) |
| R1 [I > 2σ(I)] | 0.0631 | 0.0549 | 0.0488 | 0.0719 |
| wR2 [I > 2σ(I)] | 0.1503 | 0.1374 | 0.1086 | 0.2013 |
| GOF | 1.101 | 1.126 | 1.187 | 1.050 |
| [decc][PS] | |
|---|---|
| formula | C41H34N2O3S·CH3OH |
| fw | 666.80 |
| crystal size, mm | 0.30 × 0.22 × 0.10 |
| crystal system | monoclinic |
| space group | P21/n (no. 14) |
| a, Å | 14.4690(15) |
| b, Å | 14.4551(12) |
| c, Å | 18.1193(17) |
| α, deg | 90 |
| β, deg | 104.764(3) |
| γ, deg | 90 |
| V, Å3 | 3664.5(6) |
| ρcalcd, g cm–3 | 1.345 |
| Z | 4 |
| T, K | 287(2) |
| μ, mm–1 | 0.132 (Mo Kα) |
| no. of reflns | 35 126 |
| no. of unique reflns | 8334 |
| variables | 445 |
| λ, Å | 0.71075 (Mo Kα) |
| R1 [I > 2σ(I)] | 0.0971 |
| wR2 [I > 2σ(I)] | 0.2389 |
| GOF | 0.921 |
Computation Detail
Ab initio calculations at B3LYP/6-31G(d,p) and B3LYP/LANL2DZ levels were carried out by using the Gaussian 16 program.25
Acknowledgments
Theoretical calculations were performed at the Research Center for Computational Science, Okazaki, Japan. The synchrotron radiation experiments were performed at the BL02B1 (2018B1714 and 2019A1704) and BL40XU (2019A1211) of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) with supports from Dr. Kunihisa Sugimoto, JASRI/SPring-8, Dr. Nobuhiro Yasuda, JASRI/SPring-8, and Kei Muzuguchi, Yamagata University.
Supporting Information Available
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.1c04986.
1H and 13C NMR spectra, UV/vis absorption and fluorescence spectra, diffuse reflectance spectra, and X-ray crystallographic data (PDF)
A part of this work was supported by the Advanced Next Generation Energy Leadership (ANGEL) project (2016–17), the Japan–Ukraine Bilateral Joint Research Project from the Japan Society for the Promotion of Science (JSPS), and JSPS KAKENHI for Early-Career Scientists (JP19K15616).
The authors declare no competing financial interest.
Supplementary Material
References
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