Two Thermostable Three-Dimensional Homochiral Metal−Organic Polymers with Quartz Topology

Two new homochiral metal−organic coordination polymers, M₂(TPOM)(d-Cam)₂(H₂O)₂ (M = Zn for 1, Cd for 2, d-H₂cam = d-camphoric acid, TPOM = tetrakis(4-pyridyloxymethylene)methane) have been prepared under solvothermal conditions and characterized by single crystal X-ray structure analyses, thermogravimetric analyses, circular dichroism, second-order nonlinear optical (NLO), and photoluminescent measurements. Compounds 1 and 2 are isostructural and crystallize in the chiral space group P2₁2₁2 (No. 18). In 1, Zn(II) is tetrahedrally coordinated, while Cd(II) in 2 is six-coordinated. Both possess a three-dimensional (3D) framework with a 4-connected node. Tetrahedral quadridentate linker TPOM connects four M(II) ions through its four peripheral pyridyl groups to form a wavelike two-dimensional (2D) sheet [M₂(TPOM)]_n. The chiral bidentate d-H₂cam ligand connects two M(II) ions to form a homochiral left-handed one-dimensional helical chain [M(d-cam)]_n. The homochiral helical chains interweave the 2D wavelike sheets via sharing the metal sites to form a 3D homochiral framework with 2-fold interpenetrating quartz (6⁴8²) topology. Both 1 and 2 are NLO-active materials and exhibit relatively high thermal stabilities.