Emission Enhancement and Chromism in a Salen-Based Gel System

Abstract

A new salicylideneaniline-based organogelator has been synthesized, and it can gelatinize organic solvents, including cyclohexane, toluene, benzene, and some mixed solvents. SEM images show that it has self-assembled into 1-D nanofibers, which further cross-link to form 3-D network. On the basis of the results of small-angle XRD and the optimized molecular length by semiempirical quantum calculations, the gelators are supposed to pack into a unimolecular lamellar structure with a period of 3.01 nm. Significantly, reversible chromism is realized with respect of the tautomerism between the NH and OH forms during the sol-gel freezing repetition. Furthermore, the gel can emit intense green light, and the fluorescent quantum yield of the gel is approximately 600 times higher than that of the solution. The aggregation-induced emission enhancement is ascribed to the formation of J aggregation and the inhibition of intramolecular rotation in the gel state.

Photoisomerization of a Maleonitrile‐Type Salen Schiff Base and Its Application in Fine‐Tuning Infinite Coordination Polymers

“…Many salen Schiff bases with intramolecular hydrogen bonds undergo excitedstate intramolecular proton transfer (ESIPT). [10] However, ESIPT was not observed in either 1Z or 1E, plausibly due to the dominant intramolecular charge-transfer (ICT) effect, such that solvent dipole relaxation greatly stabilizes 1Z* (or 1E*) in the equilibrium polarization and hence prevents ESIPT. Several relevant cases have been reported recently.…”

Copper(ii)-responsive gel–sol phase transition in supramolecular gel systems of salen-appended sorbitol

“…So far the salicylideneaniline moiety has become a useful building block for 35 the construction of supramolecular architectures. [21][22][23][24][25] For example, it has been found that the crystals of salen (N,Nbis(salicylidene)-o-phenylenediamine) were thermochromic, nearly colorless at 77 K but orange at room temperature, and gave strong fluorescence emission as a result of the formation of J 40 aggregates in the crystals. 22 Herein, we have designed and synthesised a salen-linked gelator 1 (Scheme 1), composed of naphthalene-based 45 salicylideneaniline segment (salen) and a sorbitol group that can form intermolecular extended H-bonging and accordingly is widely employed as one of gelating groups.…”

Self‐Assembly of Schiff Base Organogelator with Enhanced Fluorescence Emission

“…[9][10][11][12][13][14][15][16][17][18][19] Recently, there has been increasing interest in the development of fluorescent organogels constructed from π-conjugated low molecular weight gelators due to their academic importance and promising applications in optoelectronics, fluorescence sensors, etc. [20][21][22][23][24][25][26] However, most π-conjugated molecules, employed as building blocks to fabricate nanostructures, lose their fluorescence when assembled into the condensed phase owing to the formation of detrimental excimers or exciplexes, although they emit efficiently in the solution state.…”

“…Datta et al [31] synthesized a gallic acid derived salicylideneaniline gelator. Lu et al [32,34] reported two organogels based on cholesterol connected salicylideneaniline derivatives. Most Schiff bases gelators reported contain ortho-hydroxy substituents in the aromatic ring, namely salicylideneanilines.…”