Phase-Matching Second-Harmonic Generation in Zero-Dimensional Zinc Thiocyanates Ligated with Chiral Amino Acids.

Two organic-inorganic hybrid solids, namely, Zn(SCN)2(L-C9H11NO2)2 (1) and Zn4(SCN)4(L-C5H8NO3)4(H2O)4 (2), were synthesized by incorporating chiral amino acids into the zinc thiocyanate system. Compound 1 crystallizes as a monomeric complex in the noncentrosymmetric space group P21, while compound 2 features a circular tetrameric structure crystallized in the noncentrosymmetric space group P21212. Both compounds exhibit phase-matching second-harmonic generation (SHG) responses, which are 1.4 and 3.1 times that of KH2PO4, respectively. Theoretical calculations were conducted to determine the source of their SHG responses.