Achieving Different Color Changes for Photochromic Compounds by Controlling Coordination Modes

Abstract

Photochromic materials with different color changes are highly desirable for color indicators, anticounterfeiting marks, decoration, and other applications. Group modification and coordination with metals are common methods to obtain such materials. This work demonstrates that different coordination modes can acquire different color changes. Two known compounds, [Zn(suc)(bipy)]n (1) and [Zn2(mal)2(μ-bipy)(H2O)2·2(H2O)0.25]n (2) (suc = succinate, mal = malonate, bipy = 4,4′-bipyridine), exhibit different photochromic behaviors: compound 2 with dicoordinated bipy groups shows significant red-shift absorption compared to 1 with monocoordinated bipy groups after illumination. This discovery provides a new idea to develop photochromic materials with tailored color changes.