Reversible photo/thermal solid-state transformation of a coordination polymer

A 2D coordination polymer, 1, was synthesized, characterized, and investigated with single-crystal-to-single-crystal photoreaction and thermal pyrolysis. It could undergo two-step photoaddition upon UV irradiation: at the first step, the parallel polycatenated 2D topology of the structure changed into 4-fold interpenetrating 3D nets; at the second step, a new compound with an unreported 3D net topology was formed. Upon heating, the cyclobutanes in the photoreaction product underwent a ring opening reaction. The photoluminescence of 1 was determined by its structure; it emitted green fluorescence, and after photoaddition and photopolymerization, it emitted blue fluorescence. 1 may be a photo/thermo-switchable dual-color green-to-blue fluorescence material.