Photochromism of supramolecular assemblies based on benzenecarboxylate donors and viologen acceptors

Abstract

Similar viologen acceptors, a regular change in donor moieties and photochromism provide an ideal model for elucidating D–A matching rules.

Multifunctional Viologen-Derived Supramolecular Network with Photo/Vapochromic and Proton Conduction Properties

“…The electron transfer process was verified by solid-state UV-vis adsorption spectra and electron paramagnetic resonance (EPR). As shown in Figure 3 b, two new characteristic absorption bands around 420 and 630 nm appear after UV irradiation [ 17 , 36 , 37 , 38 ]. Moreover, an intensive signal with g = 2.00 occurs, indicating the generation of viologen radicals in 1 during the photochromic process ( Figure 3 c).…”

“…In contrast to the large number of chromic MOFs, supramolecular networks containing bipyridinium carboxylate unit are still rare [ 16 , 17 ], and the further research to understand the chromic mechanism and enhance the chromic properties of supramolecular networks is highly desirable [ 18 ]. On the other hand, supramolecular networks possessing hydrophilic groups (such as -COOH, -SO 3 H and -PO 3 H 2 ) and well-defined hydrogen bond paths may be eligible proton conductors for hydrogen fuel-cell applications [ 19 , 20 ].…”

The photochromic behaviour of two viologen salts modulated by the distances between the halide anions and the cationic N atoms of viologen

“…The zigzag chains are zippered into two-dimensional (2D) wave-like layers through hydrogen-bond interactions (C2-H2Á Á ÁCl1 i , C10-H10Á Á Á N3 ii and C11-H11BÁ Á ÁCl1 iii ). The 2D layers are further assembled into a three-dimensional (3D) supramolecular structure throughinteractions involving the pyridine rings [the centroid-centroid distance is 3.7182 (16) Å ], C-HÁ Á ÁCl interactions (C2-H2Á Á ÁCl1 i , C11-H11AÁ Á ÁCl1 and C11-H11BÁ Á ÁCl1 iii ) and electrostatic forces (Liu et al, 2019). It should be noted that the distances between alkylated pyridinium N + cations and neighbouring Cl À anions are 3.931 (18) and 4.083 (17) Å , which have been considered to be important parameters for the formation of radicals through stimuliinduced electron transfer.…”

Metal–organic framework bearing new viologen ligand for ammonia and Cr2O72− sensing

“…At the same time, MOFs designed based on viologen have advantages in chemical sensing/switching and other elds, and their response characteristics can be adjusted by the organization of the D-A block. 1,2,14,15,17,[28][29][30][31][32][33][34][35][36] Ammonia (NH 3 ) is an important industrial raw material with a wide range of uses, but it is also a highly toxic chemical. And even at low concentrations, there is a certain degree of toxicity.…”