Explorations of Second-Order Nonlinear Optical Materials in the Monovalent Trithiocyanurate System
Xia Hao, Chensheng Lin, Ning Ye, Donghong Lin, Dan Zhao, Yuqiao Zhou, Enbo Shangguan, Min Luo
Abstract
Two π-conjugated trithiocyanurates A(H2C3N3S3) (A = NH4, Cs) were successfully synthesized via a mild aqueous solution method or hydrothermal technique, and the ammonium bicarbonate and cesium hydroxide were used as deprotonation agents. NH4(H2C3N3S3) crystallizes in a symmetric space group P1̅ with flat [H2C3N3S3]∞ chain separated by NH4+, whereas Cs(H2C3N3S3) belongs to an asymmetric space group Cc [Z = 4, a = 5.405(6) Å, b = 21.263(3) Å, c = 14.996(2) Å, β = 92.408(10)°] with wavy [H2C3N3S3]∞ chain separated by Cs+. More importantly, Cs(H2C3N3S3) displays a strong second-harmonic generation effect (4.6 × KH2PO4), a large birefringence (Δn = 0.196@1064 nm), and a thermal stability up to 271.3 °C. In addition, a theoretical study further reveals that the π-conjugated (H2C3N3S3)− group has made a primary contribution toward enhancing the linear and nonlinear optical properties in the above two compounds.