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. 2026 Sep 9;11(37):55939–55949. doi: 10.1021/acsomega.6c05779

Morphological Study on the Gelation-Induced Phosphorescence of All-Organic Phosphors Based on Substituted Benzil

Sae Hui Lee 1, Marco S Valverde Paredes 1, Paul M Forster 1, Dong-Chan Lee 1,*
PMCID: PMC13613408  PMID: 42798883

Abstract

We report gelation-induced phosphorescence at room temperature based on 4,4’-disubstituted benzils with alkyloxy and ester groups. The title compounds include five 4,4’-dialkyloxybenzils with varying alkyl chain lengths (from octyloxy to dodecyloxy) and two 4,4’-diesterbenzil (nonylester and phenyl ester). All of the title compounds showed excellent gelation properties in hydrocarbon, alcohol, and acetonitrile solvents. The room-temperature phosphorescence was turned on upon gelation, whereas no emission was observed in solution. The investigation of the photophysical properties of the dried gels (xerogels) revealed that the length of the alkyloxy side group significantly influenced the phosphorescence lifetime (τ) and quantum yield (Φp). BZL-OC8, -OC9, and -OC10 showed better phosphorescence performance than their longer chain counterparts (BZL-OC11 and -OC12). The maximum τ of 1.28 ms and Φp of 43% were achieved for 4,4’-dinonyloxybenzil (BZL-OC9). Powder X-ray diffraction patterns suggested that BZL-OC11 and -OC12 may adopt different molecular packing modes that may not facilitate the restriction of intramolecular motion as efficiently as in the shorter-chain molecules. The ester-substituted benzils showed inferior phosphorescence to BZL-OC9. Between the two ester-substituted benzils, nonylester (BZL-EstC10) outperformed phenylester (BZL-EstPh). Interestingly, the title compounds showed strong gelation solvent-dependent phosphorescence. This indicates that the appropriate choice of gelation solvent is crucial for efficient fiber growth. For BZL-OC8 and -OC9, ethanol and decane gels were superior to the acetonitrile gel. In the case of BZL-EstC10, ethanol was a better solvent than hexane. 1,1,1-Trichloroethane was found to be the best gelation solvent for phosphorescence in BZL-EstPh. Polarized optical microscopy and scanning electron microscopy confirmed the presence of fibers in the xerogels. In addition, the dependence of phosphorescence on the alkyloxy length and gelation solvent was strongly correlated with the fiber morphology. In general, longer and thicker fibers were associated with better phosphorescence performance. This study successfully proved that properly substituted benzils can turn on room-temperature phosphorescence via gelation, which could be used as an application-friendly processing method.

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Introduction

Crystallization-induced phosphorescence (CIP) has emerged as a promising approach to achieve room-temperature phosphorescence (RTP) of metal-free, all-organic phosphors. Typically, CIP-active molecules do not exhibit any emission in the solution state due to the loss of excited-state energy through molecular motion. In the crystalline state, molecular motions are restricted within the crystal lattice, enabling phosphorescence to be activated. Numerous CIP molecules have shown excellent phosphorescent performance without the need for an inert atmosphere, low temperatures, or a polymer matrix.

Despite the remarkable advancements, CIP requires a delicate, time-consuming recrystallization process. Controlling crystal quality and size depends on multiple parameters, such as nucleation density, concentration, temperature, cooling rate, etc. Consequently, the crystal quality and size can vary from operator to operator, making reproducibility a significant challenge. The rigid three-dimensional (3D) structures of crystals also make them inappropriate for practical applications. To enhance their utility, it is imperative to develop an alternative processing method that circumvents the stringent crystallization conditions of current RTP systems. Currently, non-CIP organic RTP materials are limited, and most instances of RTP are achieved through polymers, − carbon dots, − multicomponent host-guest systems, − or metal-organic frameworks. ,

As an alternative, organogelation could be an excellent approach to achieve RTP. Organogels are formed by solvent molecules being trapped and immobilized within a 3D network of 1D fibers. These 1D fibers are formed through various non-covalent interactions, such as hydrogen bonding, π-π interactions, and van der Waals interactions. Organogels are easy and quick to prepare through simple heating and cooling processes. They show flexible gel-sol transitions with thermoreversibility and reproducibility. Efficient organogelators should promote fiber growth in one direction more preferentially than in the other two. Therefore, the leading driving force (intermolecular interactions) should be present to encourage 1D fiber growth, while the other two directions should afford interactions with solvent molecules to impede growth. Multiple reviews are available regarding the structural requirements for inducing gelation. Among these, π-cores with alkyl substituents have proven to be an effective molecular platform for low-molecular-weight organogelators (LMOGs). π-LMOGs are of particular interest for their electronic and optical properties, including electron transfer, energy transfer, , charge transport, − electrical conductivity, , luminescence, tunable emission, etc. They have been applied in devices such as organic field-effect transistors (OFETs), organic solar cells (OSCs), and imaging and sensing applications. −

Considering the aforementioned benefits, organogelation could be a potentially promising approach to induce RTP as a facile and reproducible method suitable for a wide range of applications. Indeed, the utility of organogelation in achieving RTP, especially with single-component gelators, has been actively explored by a few research groups. − The rigidity of gel matrices has been confirmed to facilitate ultralong RTP. At the same time, the sensitive stimulus-responsiveness of organogels has enabled dynamic anti-counterfeiting applications. Most reported single-component RTP gelators are benzophenone derivatives with expanded π-surface, featuring non-conventional organogelator structures. In these structures, alkyl side groups, a typical structural component of LMOGs, are absent to avoid the non-radiative decay of excitons caused by flexible alkyl chains. Notably, gelation studies on all-organic phosphors with hydrocarbon side groups remain rare. Understanding the effect of such side groups on producing LMOGs that can induce gel-induced phosphorescence (GIP) would be highly beneficial for guiding future molecular design. In this work, as a proof of concept, we employed benzil as a phosphor and modified it with alkyloxy and ester side groups to investigate their efficacy as organogelators. Benzil exhibits prominent intersystem crossing (ISC), and its non-planar geometry is beneficial in preventing aggregation-caused quenching. Indeed, benzil has shown CIP properties as a result of the restriction of intramolecular motion. Interestingly, when benzil was substituted with methoxy groups at the 4 and 4’ positions (p-anisil), the phosphorescence lifetime and quantum yield were improved by 5- and 13-fold, respectively. Elongation in the alkyloxy chain length further improved phosphorescence performance. , Based on our earlier crystallographic study, octyloxy-substituted benzil exhibited greater alkyl-driven assembly compared to p-anisil. The enhanced van der Waals interactions between alkyl side groups can facilitate organogelation. Therefore, we believe that properly substituted benzil can function as an LMOG through synergistic intermolecular interactions. Five alkyloxy- and two ester-substituted benzils presented in this work demonstrated excellent gelation ability in various organic solvents. In-depth investigations of their gelation characteristics were performed and discussed along with their phosphorescence properties. Furthermore, correlations between phosphorescence performance and morphology were established based on scanning electron microscopy and optical microscopy characterization.

Results and Discussion

Figure shows the molecular structures of the title compounds. The synthetic procedures for BZL-OCn (n = 8–12) have been described in our earlier publication.

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Molecular structures of substituted benzil compounds.

BZL-EstC10 and -EstPh were prepared by the reactions of 4,4’-dihydroxybenzil with decanoyl chloride and benzoyl chloride, respectively, in the presence of triethylamine, giving high yields (80–90%). ,

The organogelation was tested in various organic solvents using an inverted-vial method. Four different categories of solvents were used for the gelation test: nonpolar hydrocarbons, polar solvents, aromatic solvents, and halogenated solvents. All the title compounds showed excellent gelation ability in select organic solvents. Gelation properties and critical gelation concentrations (CGCs) are summarized in Table . The CGCs are presented in both mM and wt %. BZL-OCn compounds formed gels in long straight-chain hydrocarbon solvents (decane and hexadecane), but not in hexane or cyclohexane. They also gelled polar solvents, including ethanol, 1-propanol, and acetonitrile. Halogenated solvents, aromatic solvents (toluene), and ethyl acetate did not form gels, presumably due to the high solubility of BZL-OCn compounds in those solvents. In all gelling solvents, BZL-OC8, -OC9, -OC10, OC11, and -OC12 were considered to be good gelators (CGC: 1–10 wt %). BZL-EstC10 gelled in all nonpolar hydrocarbon solvents tested except for toluene. It also gelled polar solvents, including short-chain alcohols and acetonitrile. Overall, its CGCs were higher than those of the other compounds. Nevertheless, BZL-EstC10 can be considered to be a good gelator for all gelling solvents. BZL-EstPh gelled in cyclohexane, decane, hexadecane, 1,1,1-trichloroethane (TCE), ethanol, 1-propanol, and acetonitrile. BZL-EstPh can be regarded as a supergelator (CGC < 1 wt %) in decane and ethanol and as a good gelator in all other gelling solvents.

1. Gelation Properties of the Title Compounds in Various Organic Solvents .

Solvent BZL-OC8 BZL-OC9 BZL-OC10 BZL-OC11 BZL-OC12 BZL-EstC10 BZL-EstPh
cyclohexane S S S S S G (72/5.09) G (48/2.78)
hexane S S S S S G (80/6.69) NS
decane G (40/2.50) G (40/2.69) G (25/1.78) G (25/1.87) G (16/1.26) G (104/7.79) G (12/0.68)
hexadecane G (40/2.41) G (40/2.56) G (40/2.71) G (30/2.14) G (25/1.86) G (80/5.70) G (32/1.83)
toluene S S S S S S S
ethyl acetate S S S S S S S
THF S S S S S S S
TCE S S S S S S G (48/1/64)
DCE S S S S S S S
methanol NS NS NS NS NS G (64/4.46) NS
ethanol G (50/2.96) G (30/1.88) G (20/1.33) G (20/1.40) G (20/1.47) G (64/4.47) G (12/0.69)
propanol G (50/2.65) G (40/2.47) G (29/1.89) G (27/1.85) G (25/1.80) G (64/4.39) G (24/1.35)
acetonitrile G (63/3.78) G (30/1.91) G (20/1.35) G (20/1.42) G (25/1.86) G (80/5.67) G (48/2.78)
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a

Abbreviations: G, gel; PPT, precipitation upon cooling; S, soluble after cooling (solubility was tested up to 100 mM); THF, tetrahydrofuran; TCE, 1,1,1-trichloroethane; and DCE, 1,2-dichloroethane. The critical gelation concentration (CGC) is shown in parentheses (mM/wt %).

All the title compounds exhibited emission in gel form but not in solution. For example, there was no emission for BZL-EstC10 in solution (Figure a and c); however, it became emissive in the gel state (Figure b and d). BZL-OC8, BZL-OC9 (Figure e), BZL-OC10, and BZL-OC11 formed blue-emissive gels, while BZL-OC12 (Figure f) formed a green-emissive gel. Both BZL-EstC10 and BZL-EstPh gels emitted a green color.

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BZL-EstC10 in DCM solution (a and c) and ethanol gel (b and d). BZL-OC9 ethanol gel (e) and BZL-OC12 ethanol gel (f). c–f are under a handheld UV lamp (365 nm). Gels were made at their respective CGC.

To characterize the photophysical properties, a dried form of the title compound’s gel (xerogel) was prepared. Xerogels of all title compounds were prepared from ethanol gels to allow proper comparison.

As shown in Figure , λem’s of all the blue gels (BZL-OC8, -OC9, -OC10, and -OC11) were identical at 478 nm. BZL-OC12 showed a red-shifted λem at 503 nm, along with a shoulder at ca. 550 nm. In the case of BZL-EstC10, λem was further red-shifted to 516 nm, while the λem of BZL-EstPh was the longest, at 538 nm. To understand the origin of the emission, emission spectra were recorded as a function of delay time (T d) from 0 to 1 ms. Any emission with T d longer than 0.1 ms excludes a fluorescence contribution, and therefore emission at T d longer than 0.1 ms reveals the presence of phosphorescence. As shown in Figure , BZL-OC8, BZL-EstC10, and BZL-EstPh showed negligible spectral changes, including λem regardless of T d. There was only a slight decrease in emission intensity up to T d = 0.1 ms, and the degree of decrease was ca. 5%, 11%, and 4% for BZL-OC8, BZL-EstC10, and BZL-EstPh, respectively. This confirms that the origin of the title compound’s emission is mostly due to phosphorescence, with a minor contribution from fluorescence.

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Prompt emission of the title compounds as xerogels. All xerogels were prepared from EtOH gels, except for BZL-EstPh (TCE).

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Emission spectra of the xerogels of (a) BZL-OC8, (b) BZL-EstC10, and (c) BZL-EstPh under various delay times (T d).

Two major parameters of the xerogels for phosphorescence performance, lifetime (τ) and quantum yield (Φp) were measured and summarized in Table and Figure . For adequate comparison, the xerogels of the title compounds prepared from ethanol (EtOH) will be discussed first. In the case of BZL-OCn, the dependence of τ and Φp on the length of the alkyloxy side group was clearly observed. BZL-OC8 showed τ and Φp of 1.06 ms and 38%, respectively. When the side group was changed to nonyloxy (BZL-OC9), those values increased to 1.28 ms and 43%. These are the highest among the BZL-OCn compounds. A further increase in the carbon number (BZL-OC10) decreased τ and Φp to levels similar to those of BZL-OC8. For BZL-OC11 and -OC12, phosphorescent performance deteriorated significantly. Presumably, the higher conformational freedom of the longer side groups impeded efficient solid-state assembly and triggered greater non-radiative dissipation of triplet excitons. The study verified that there was an optimal alkyl chain length to achieve good phosphorescence performance. Note that a similar trend was observed in BZL-OCn crystals. Xerogels of ester-substituted benzil showed relatively diminished phosphorescence performance compared with BZL-OCn xerogels with n = 8, 9, and 10. For both τ and Φp, BZL-EstC10 outperformed BZL-EstPh.

2. Lifetime (τ) and Quantum Yield (Φp) of the Xerogels of the Title Compounds from EtOH Gels.

  τ (ms) Φp (%)
BZL-OC8 1.06 38
BZL-OC9 1.28 43
BZL-OC10 1.09 37
BZL-OC11 0.45 16
BZL-OC12 0.43 14
BZL-EstC10 1.13 25
BZL-EstPh 0.73 11
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Lifetime (τ) and phosphorescence quantum yield (Φp) of BZL-OCn xerogels (from EtOH).

Interestingly, the phosphorescence characteristics of both alkoxy- and ester-substituted benzils depended strongly on the gelation solvent. To study the solvent dependence, we prepared acetonitrile (AN) and decane xerogels of BZL-OC8 and compared them with the EtOH xerogel. As shown in Figure S10a, the AN xerogel had the shortest τ value of 0.6 ms. The decane xerogel showed a slightly increased τ of 0.88 ms. These values are shorter than the τ of the EtOH xerogel (1.06 ms). In the case of Φp, the AN xerogel was again the lowest at 18%. However, the decane xerogel showed a slightly higher Φp of 41% than the EtOH xerogel (38%). We note that the BZL-OC9 xerogels exhibited a very similar trend of solvent dependence (Figure S10b). Interestingly, the decane xerogel of BZL-OC9 showed a Φp of 60%, which was 1.4 times higher than that of the EtOH xerogel (43%).

In the case of BZL-EstC10, xerogels were prepared from EtOH, AN, and hexane (Figure S13a). Unlike BZL-OCn, BZL-EstC10 did not gel decane, and therefore hexane was chosen as a hydrocarbon gelation solvent. In this case, the hexane xerogel showed the shortest τ of 0.4 ms and the lowest Φp of 8%. Polar AN improved both parameters (τ = 0.97 ms and Φp = 21%), and more polar EtOH produced the highest values. BZL-EstPh xerogels were prepared from EtOH, AN, cyclohexane, and TCE (Figure S13b). Among the four xerogels, the TCE xerogel exhibited the highest performance, with a τ of 1.44 ms and a Φp of 25%. The other three xerogels showed reduced τ (1.04 ms for AN, 0.86 ms for cyclohexane, and 0.73 ms for the EtOH xerogel) and Φp (14% for AN and 11% for both cyclohexane and EtOH xerogels). The solvent-dependent phosphorescence suggests that solid-state assembly to maximize phosphorescence performance can be controlled by selecting an appropriate gelation solvent.

To gain deeper insight into the relationship between the xerogel’s phosphorescence performance and morphology, the xerogels were characterized by polarized optical microscopy (POM) and scanning electron microscopy (SEM). The optical micrographs of EtOH xerogels of the BZL-OCn compounds with and without cross-polarization are shown in Figure S14. The SEM images of these xerogels are shown in Figure . Since both characterization methods showed very similar morphological features, we will focus on the SEM results for the BZL-OCn xerogels. BZL-OC8 (Figure a) and BZL-OC9 (Figure b) both showed a belt-like morphology, with BZL-OC9 showing significantly thicker, straighter, and longer fibers than BZL-OC8. Also, more bundling was observed from BZL-OC8 while BZL-OC9 formed individual fibers. BZL-OC10 also showed a long fibrous morphology (Figure c). The fibers were thinner and flatter compared with the BZL-OC9 fibers. Then, a dramatic transition in morphology was observed in BZL-OC11, which had an extremely thin, flat, and torn, paper-like morphology (Figure d). The growth of BZL-OC11 fibers was extensive in both the length and width directions, generating two-dimensional flat sheets. The striking transition in fiber growth in BZL-OC11 manifests an obvious shift in the molecular assembly pattern compared with its shorter alkyl-chain counterparts. In the case of BZL-OC12, belt-like fibrous features were regained (Figure e). However, the fibers were significantly shorter and thinner and exhibited more nucleation than the BZL-OC8, -OC9, and -OC10 counterparts. The general trend observed from the POM and SEM images is that a side group longer than decyloxy may hamper proper intermolecular interactions in the thickness direction and impede proper fiber growth. More SEM images at lower magnification are also provided in Figure S15.

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SEM images of BZL-OCn ethanol xerogels. (a) BZL-OC8, (b) BZL-OC9, (c) BZL-OC10, (d) BZL-OC11, and (e) BZL-OC12. Scale bar: 10 μm.

The phosphorescence performance of the title compounds was clearly associated with the fiber morphology. Compounds with shorter alkyl chain lengths, such as BZL-OC8, -OC9, and -OC10 xerogels, which showed outstanding phosphorescence performance, exhibited effective fiber growth. On the other hand, compounds with longer alkyl chain lengths, such as the BZL-OC11 and -OC12 xerogels, which showed relatively poor phosphorescence performance, exhibited ineffective fiber growth. It was found that the main driving force for BZL-OC8 assembly was alkyl–alkyl interactions, as determined by single-crystal crystallography. Octyloxy, nonyloxy, and decyloxy groups may have provided appropriate alkyl–alkyl interactions, which allowed for better molecular assembly upon gelation. For longer side chains, the crucial alkyl–alkyl interactions may have been significantly limited because of the increased conformational freedom.

BZL-OC8 xerogels showed solvent-dependent phosphorescence; therefore, we examined their morphologies as a function of the gelation solvent. As shown in Figure a, the AN xerogel exhibited shorter fibers with twisting and braiding. The fibers, although not uniform, had lengths of approximately 100 μm. The fiber widths varied from ca. 0.3 μm to 1.2 μm. Noticeably enhanced fiber growth was observed in the decane xerogel (Figure b), with fibers even longer and thicker than those in the EtOH xerogel.

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SEM images of a) BZL-OC8 xerogel from AN, b) BZL-OC8 xerogel from decane, c) BZL-EstC10 xerogel from EtOH, and d) BZL-EstPh xerogel from TCE. Scale bar: 50 μm.

For BZL-EstC10, xerogels were prepared from hexane (Figure S16a), AN (Figure S16b), and ethanol (Figure S16c) to investigate morphological differences. The optical micrograph of the hexane xerogel showed short and narrow fibers with irregular sizes throughout. In the case of the AN xerogel, thin fibers were absent, and the morphology resembled thin, plate-like flakes. The EtOH xerogel showed a similar morphology to the AN xerogel but with a smaller flake size. The SEM image of the EtOH xerogel (Figure c) confirmed the morphology observed in the POM study. Note that the BZL-EstC10 xerogel from hexane showed the lowest phosphorescence performance, while xerogels from AN and EtOH showed relatively high performance. In the case of BZL-EstPh, all the xerogels prepared from EtOH (Figure S17a), cyclohexane (Figure S17b), AN (Figure S17c), and TCE (Figure d and S16d) showed 1D fiber morphologies, and the major difference was the size of the fibers. Among them, the TCE xerogel formed longer, thicker, and more rigid fibers.

Powder X-ray diffraction (PXRD) was performed on the EtOH xerogels of the BZL-OCn molecules. Our approach to sample preparation was to minimize any handling that might affect crystallinity; some preferred orientations are likely, given the fibrous morphology of the materials. Comparison of the PXRD data for BZL-OC8 with a simulated diffraction pattern based on the previously published single-crystal X-ray diffraction (SCXRD) structure revealed similar diffraction patterns, with slightly larger d-spacings in the xerogel, indicating that the two crystal structures are closely related (Figure S18). The structure measured previously was not solvated. The larger unit cell observed in the PXRD data for the EtOH xerogel suggests that some solvent may be incorporated into a similar packing arrangement of the BZL-OC8 molecules. The experimental PXRD patterns of BZL-OC9 and -OC10 xerogels were quite similar to those of the BZL-OC8 xerogel (Figure ). This result supports similar molecular arrangements for BZL-OC9 and -OC10 xerogels as are seen in the BZL-OC8 SCXRD structure. For the BZL-OC11 and -OC12 xerogels, the PXRD pattern is substantially different, suggesting that the molecular packing is different from that of the shorter-chain molecules. The molecular packing for BZL-OC11 and -OC12 may not facilitate the restriction of intramolecular motion as efficiently as in the shorter-chain counterparts, which may result in a deterioration in phosphorescence performance.

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PXRD patterns of BZL-OCn xerogels from EtOH.

Although the phosphorescence performance and morphology were affected by the gelation solvent, PXRD patterns showed the same crystal structure regardless of the gelation solvent, as shown in Figure S19 for BZL-EstC10 (EtOH and hexane xerogels) and Figure S20 for BZL-EstPh (EtOH and TCE xerogels). The PXRD results suggest that the gelation solvent does not change the molecular packing mode of the fibers formed. On the basis of the morphology study, different gelation solvents may facilitate the growth of self-assembled clusters to different degrees. For example, the structural similarity of decane to the octyl side group in BZL-OC8 may have induced local interactions between the solvent and the alkyl side group, which could help align the side group, resulting in greater fiber growth. However, in the case of BZL-EstC10, perhaps due to a length mismatch between the nonyl side group and hexane, the gelation solvent may not promote efficient fiber growth.

Conclusions

In this work, we have successfully prepared purely organic RTP organogelators using benzil as a molecular platform. All the title compoundsfive alkyloxy-substituted benzils (BZL-OCn) with different alkyl lengths (octyloxy to dodecyloxy) and two ester-substituted benzils (BZL-EstC10 and -EstPh)showed excellent gelation capabilities in various organic solvents with different polarities. All the gelators can be classified as good or supergelators. The gelation turned on RTP, whereas no emission was observed in solution. Photophysical characterization of the BZL-OCn EtOH xerogels showed that there was a strong correlation between τ and Φp and the alkyl length. The nonyloxy group (BZL-OC9) was found to be the optimal length to achieve the highest Φp and τ values, 43% and 1.28 ms, respectively. Further increases in the alkyl length deteriorated the phosphorescence performance. EtOH xerogels from the ester substituted benzils showed inferior phosphorescence performance compared to BZL-OC8, -OC9, and -OC10.

The phosphorescence performance was strongly dependent on the type of gelation solvent. For BZL-OC8 and -OC9, the AN xerogel had the shortest τ and lowest Φp, while the EtOH and decane xerogels had much improved performances. For BZL-EstC10 and -EstPh, EtOH and TCE, respectively, proved to be the best gelation solvents for phosphorescence.

The morphological study using POM and SEM proved that the gelation involves fibrillation. Besides, the effect of alkyl length and gelation solvent on the phosphorescence performance was strongly correlated with the fiber morphology. In general, thicker, straighter, and longer fibers were associated with better Φp and τ, as shown by the EtOH xerogel of BZL-OC9 compared to other BZL-OCn xerogels. PXRD patterns showed that BZL-OC8, -OC9, and -OC10 xerogels have a similar molecular packing mode to that of the single crystal of BZL-OC8. However, BZL-OC11 and -OC12 adopted different molecular packing modes compared to shorter alkyloxy counterparts. A similar morphological effect on phosphorescence performance was observed when gelation solvents with different polarities and sizes were employed (e.g., decane vs AN for BZL-OC8, EtOH vs hexane for BZL-EstC10, and TCE vs EtOH for BZL-EstPh). The type of gelation solvent seems to have a great impact on fiber growth without altering the molecular packing mode, as revealed by PXRD characterization. Unlike all other BZL-based organogelators, BZL-EstC10 grew two-dimensional, flaky, thin plates. These results indicate that properly substituted phosphors and appropriate gelation solvents are key to producing desired phosphorescence performance.

The current study provides an in-depth investigation of side-group effects on gelation capabilities and the resulting phosphorescent properties. We also verified that GIP is an effective tool, allowing rigid solid-state assembly to turn on phosphorescence. The fact that GIP is facile and reproducible will encourage further development of purely organic RTP gelators with improved molecular designs to enhance phosphorescent properties.

Supplementary Material

ao6c05779_si_001.pdf (2.5MB, pdf)

Acknowledgments

The authors gratefully acknowledge Mr. Jung Jae Koh in the Department of Chemistry & Biochemistry at the University of Nevada, Las Vegas, for assistance with mass spectrometry. The authors also thank Dr. Daniel Koury in the Department of Chemistry & Biochemistry at the University of Nevada, Las Vegas, for providing access to the powder X-ray diffractometer.

All data supporting the findings of this work are included in the article and its Supporting Information.

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.6c05779.

  • Detailed synthetic procedures and characterizations of BZL-EstC10 (Figures S1–S3) and BZL-EstPh, (Figures S4–S6), time-resolved PL decay curves of BZL-OCn xerogels from EtOH (Figure S7), time-resolved PL decay curves of BZL-OC8 (Figure S8) and BZL-OC9 (Figure S9) xerogels from different solvents, lifetimes and quantum yields of BZL-OC8 and BZL-OC9 xerogels from different solvents (Figure S10), time-resolved PL decay curves of BZL-EstC10 (Figure S11) and BZL-EstPh xerogels (Figure S12) from different solvents, lifetimes and quantum yields of BZL-EstC10 and BZL-EstPh xerogels from different solvents (Figure S13), POM (Figure S14) and additional SEM images (Figure S15) of BZL-OCn EtOH xerogels, optical micrographs of BZL-EstC10 (Figure S16) and BZL-EstPh xerogels (Figure S17) from different solvents, simulated and experimental PXRD patterns of BZL-OC8 (Figure S18), and PXRD patterns of BZL-EstC10 (Figure S19) and BZL-EstPh (Figure S20) from different gelation solvents (PDF)

The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

The authors declare no competing financial interest.

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