Copper(I) Thiocyanate-Amine Networks: Synthesis, Structure, and Luminescence Behavior

A series of metal-organic networks of CuSCN were prepared by direct reactions with substituted pyridine and aliphatic amine ligands, L. Thiocyanate bridging is seen in all but 1 of 11 new X-ray structures. Structures are reported for (CuSCN)L sheets (L = 3-chloro- and 3-bromopyridine, N-methylmorpholine), ladders (L = 2-ethylpyridine, N-methyl-piperidine), and chains (L = 2,4,6-collidine). X-ray structures of (CuSCN)L-2 are chains (L = 4-ethyl- and 4-t-butylpyridine, piperidine, and morpholine). A unique N-thiocyanato monomer structure, (CuSCN)(3-ethylpyridine)(3), is also reported. In most cases, amine ligands are thermally released at temperatures <100 degrees C. Strong yellow-to-green luminescence at ambient temperature is observed for the substituted pyridine complexes. High solid state quantum efficiencies are seen for many of the CuSCN-L complexes. Microsecond phosphorescence lifetimes seen, for CuSCN-L are in direct contrast to the nanosecond-lifetime emission of CuSCN. MLCT associated with pyridine pi* orbitals is proposed as the excitation mechanism.