State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, 2699#, Qianjin Street, Changchun, China.
Chemistry. 2009 Sep 28;15(38):9824-35. doi: 10.1002/chem.200900732.
Glutamine derivative 1 with two-photon absorbing units has been synthesized and was found to show gelation ability in some solvents. Its self-assembly in the gel phase could be controlled by the solvent and speed of gelation. For example, in DMSO the organogelator self-assembled into H-aggregates with weak exciton coupling between the aromatic moieties. On the other hand, in DMSO/diphenyl ether (1:9, v/v) the molecules formed 1D aggregates, but with strong exciton coupling due to the small distance between the chromophores. Moreover, the formation of these two kinds of aggregates could be adjusted by the ratio of DMSO to diphenyl ether. In DMSO/toluene, DMSO/butanol, DMSO/butyl acetate, and DMSO/acetic acid systems similar results were observed. Therefore, conversion of the packing model occurs irrespective of the nature of the solvent. Notably, a unique sign inversion in the CD spectra could be realized by controlling the speed of gelation in the DMSO/diphenyl ether (1:9, v/v) system. It was found that a low speed of gelation induces the gelator to adopt a packing model with strong pi-pi interactions between the aromatic units. Moreover, the gels, when excited at 800 nm, emit strong green fluorescence and the quantum chemical calculations suggest that intramolecular charge transfer leads to two-photon absorption of the gelator molecule.
合成了具有双光子吸收单元的谷氨酰胺衍生物 1，发现其在一些溶剂中具有凝胶能力。其在凝胶相中的自组装可以通过溶剂和凝胶化速度来控制。例如，在 DMSO 中，有机凝胶剂自组装成具有弱芳构单元间激子耦合的 H-聚集体。另一方面，在 DMSO/二苯醚（1:9，v/v）中，分子形成了 1D 聚集体，但由于发色团之间的距离较小，具有强激子耦合。此外，通过 DMSO 与二苯醚的比例可以调节这两种聚集体的形成。在 DMSO/甲苯、DMSO/丁醇、DMSO/乙酸丁酯和 DMSO/乙酸体系中也观察到了类似的结果。因此，无论溶剂的性质如何，包装模型的转换都会发生。值得注意的是，通过控制 DMSO/二苯醚（1:9，v/v）体系中凝胶的凝胶速度，可以实现 CD 光谱中独特的符号反转。研究发现，凝胶速度较低会促使凝胶剂采用具有芳构单元之间强π-π相互作用的包装模型。此外，当在 800nm 激发时，这些凝胶会发出强烈的绿色荧光，量子化学计算表明，分子内电荷转移导致凝胶剂分子的双光子吸收。
