Chiral and Achiral Copper(II) Carboxyphosphonates Supramolecular Structures: Synthesis, Structures, Surface Photovoltage, and Magnetic Properties

Five chiral and achiral copper­(II) carboxyphosphonates, namely, [Cu­(4-cppH)­(2,2′-bipy)­(H2O)] (1: R-1 and S-1), [Cu9(4-cpp)6(2,2′-bipy)6] (2), [Cu3(4-cpp)2(2,2′-bipy)2] (3), [Cu3(4-cpp)2(1,10-phen)2]·4H2O (4), and [Cu­(4-cppH)­(1,10-phen)]·H2O (5), had been hydrothermally synthesized. Among them, 1 showed an unexpected 1D chiral helical chain from achiral carboxyphosphonate ligand by spontaneous resolution. In 2, the interconnection of {CuN2O3}, {CuO4}, and {CPO3} polyhedra formed a 1D chain. Such chains were further connected to a 2D layer through the carboxyphosphonates ligands. Compounds 3 and 4 were isostructural and exhibited a 2D layer, which was constructed from {CuO3N2}/{CuO4} polyhedra and the carboxyphosphonate ligands. In 5, the interconnection of neighboring {CuN2O3} polyhedra formed a dimer. These dimers were connected with the carboxyphosphonate ligands to form a chain. Interestingly, the homochiral copper­(II) phosphonate (R-1 or S-1) could be obtained by utilizing the (+)-cinchonine or (−)-cinchonidine as a chiral-inducing agent, confirmed by CD spectra. Besides, the surface photovoltage (SPV) properties of 1–5 revealed that they had positive SPV responses. The magnetic data indicated that 1, 2, 4, and 5 showed the presence of ferromagnetic couplings between magnetic centers.