Two Chiral Nonlinear Optical Coordination Networks Based on Interwoven Two-Dimensional Square Grids of Double Helices

Two new chiral two-dimensional coordination networks, ZnL2(H2O)2 (1) and CdL2(H2O)2 (2) [L = 1,2,2-trimethyl-3-(pyridin-4-ylcarbamoyl)cyclopentanecarboxylic acid], have been synthesized and structurally characterized by single X-ray structure analysis, featuring very unusual interwoven (4,4) square grids of double helices. The frameworks exhibit high thermal stability as confirmed by thermogravimetric analysis and powder X-ray diffraction studies. The unique chiral networks attributed to the chiral organic linker have led to their nonlinear optical properties.