Photochromism of two 1D coordination polymers constructed by two ligands of 1-carboxyethyl-4,4′-bipyridinium and N,N′-bis(carboxyethyl)-4,4′-bipyridinium

Abstract

In this paper, two one-dimensional (1D) coordination polymers were designed and prepared by 1-carboxyethyl-4,4′-bipyridinium (CEbpy) and N,N′-bis(carboxyethyl)-4,4′-bipyridinium (BCEbpy) ligands, i.e. {[Cu0.5(CEbpy)]·(1,2,4-H2BTC)·H2O}n (1) and {[Mn0.5(CEbpy)(H2O)]·[Mn(1,2,4-BTC)(H2O)5]·0.5(BCEbpy)·DMF·4H2O}n (2), indicating superior photochromic behavior and photoresponse properties. The crystal structures and electronic transport behaviors of two compounds were studied. Single crystal X-ray analyses reveal that compounds 1 and 2 crystallize in the triclinic space group P-1. Compound 1 exhibits intramolecular electron transport, whereas compound 2 exhibits both intramolecular and intermolecular electron transport, with a photo-response sequence that is 1 less than 2. The non-covalent interactions were investigated by the DFT method, demonstrating pi−pi interactions greatly promote the photoresponsive electron transfer for compounds 1 and 2.