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

Compounds 1 and 2 were synthesized and characterized based on different viologen ligands. They showed different structures, photochromism and applications. [Display omitted] • Two novel multifunctional Cd-viologen coordination polymers have been synthesized. • Compounds 1 and 2 exhibit high sensitivity to UV light. • Compound 2 has the ability to detect amines. 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 (H 3 BTC) under solvothermal and hydrothermal conditions results in two coordination polymers, namely, {[Cd(L1)OH]} n (1) and {[Cd(L2)(HBTC)H 2 O]·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 (NH 3 , TEA = triethylamine, MA = o-methylaniline, aniline), compound 1 displays significantly different visual color changes. [ABSTRACT FROM AUTHOR]