Second-Harmonic Generation in Organic-Inorganic Hybrid Cadmium Thiocyanates Containing Terminal Amino Acids.

Using chiral amino acids as terminal ligands, colorless crystals of Cd3(SCN)6(l-C5H9NO3)2(H2O)2·0.5CH3OH (1) and Cd(SCN)2(l-C6H14N4O2)2 (2) were obtained by a solvent evaporation method. Compound 1 has a layered structure with a moderate second harmonic generation (SHG) efficiency (0.2 × KH2PO4) and a large birefringence (0.301 at 546 nm). Compound 2 features a molecular structure with a strong SHG efficiency (2.67 × KH2PO4) and a wide band gap (4.84 eV). Theoretical calculations were performed to elucidate the origin of the large SHG response of compound 2.