Synthesis and Luminescence of Optical Memory Active Tetramethylammonium Cyanocuprate(I) 3D Networks

摘要

The structures of three tetramethylammonium cyanocuprate(I) 3D networks [NMe4]2[Cu(CN)2]2•0.25H2O (>1), [NMe4][Cu3(CN)4] (>2), and [NMe4][Cu2(CN)3] (>3), (Me4N = tetramethylammonium), and the photophysics of >1 and >2 are reported. These complexes are prepared by combining aqueous solutions of the simple salts tetramethylammonium chloride and potassium dicyanocuprate. Single-crystal X-ray diffraction analysis of complex >1 reveals {Cu2(CN)2(μ2-CN)4} rhomboids crosslinked by cyano ligands and D_3h {Cu(CN)₃} metal clusters into a 3D coordination polymer, while >2 features independent 2D layers of fused hexagonal {Cu₈(CN)₈} rings where two Cu(I) centers reside in a linear C_∞v coordination sphere. Metallophilic interactions are observed in >1 as close Cu⋯Cu distances, but are noticeably absent in >2. Complex >3 is a simple honeycomb sheet composed of trigonal planar Cu(I) centers with no Cu^…Cu interactions. Temperature and time-dependent luminescence of >1 and >2 have been performed between 298 K and 78 K and demonstrate that >1 is a dual singlet/triplet emitter at low temperatures while >2 is a triplet-only emitter. DFT and TD-DFT calculations were used to help interpret the experimental findings. Optical memory experiments show that >1 and >2 are both optical memory active. These complexes undergo a reduction of emission intensity upon laser irradiation at 255 nm although this loss is much faster in >2. The loss of emission intensity is reversible in both cases by applying heat to the sample. We propose a light-induced electron transfer mechanism for the optical memory behavior observed.