Two new multi-functional coordination polymers exhibiting photochromic behavior and amine-selective sensing capability

The self-assembly of Cd(II) ions with two kind of viologen ligands 1-(3,5-dicarboxybenzyl)-4,4'-bipyridinium chloride (H(2)L1(+)Cl(-)), 1-(3-carboxybenzyl)-4,4'-bipyridinium chloride (HL2(+)Cl(-)) and 1,3,5-benzenetricarboxylic acid (H3BTC) under solvothermal and hydrothermal conditions results in two coordination polymers, namely, {[Cd(L1)OH]}(n) (1) and {[Cd(L2)(HBTC)H2O]center dot 2H(2)O} n (2). Due to the formation of viologen radicals, they exhibit reversible photochromism through electron transfer, and the order of light response time is 2 > 1. The time-dependent density functional theory (TDDFT)-B3LYP/lanl2dz method was used to deeply understand the donor-acceptor structures, the matching rules between L and acid parts, and the intermolecular/intramolecular atom- atom close contact based on the fraction of intercontact. Compound 1 exhibit intramolecular electron transfer. Compound 2 exhibits two electron transfer modes: intramolecular and intermolecular electron transfer. In addition, when exposed to various amines (NH3, TEA = triethylamine, MA = o-methylaniline, aniline), compound 1 displays significantly different visual color changes.

Automated summary

The self-assembly of Cd(II) ions with viologen ligands under different conditions resulted in two coordination polymers. These polymers exhibited reversible photochromism through electron transfer and showed different light response times. The study also analyzed the donor-acceptor structures and the atom-atom close contacts between molecules.