Metal-directed and ligand-distorted assembly of chiral/achiral one-dimensional coordination polymers: Syntheses, structures and physical properties

The hydrothermal reactions of 5-bromoisophthalic acid (H2BIPA) and metal salts in the presence of pyridine (py) result in three new coordination polymers, namely, M(BIPA)(py)3 [M = Co(II) (1), Ni(II) (2)] and Zn(BIPA)(py)2·H2O (3), all of which have been characterized by single-crystal X-ray, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. Compounds 1 and 2 are isostructural and contain 21 helical chains made up of metal ions and BIPA2− ligand, the chains are further formed to the supramolecular structures by the π⋯π interactions between the adjacent parallel py rings. Compound 3 has a 1D chiral left-handed helical chain structure. It is notable that 3 is obtained by second order spontaneous resolution using achiral starting materials. Moreover, the solid-state CD spectrum of single crystals and powder samples of 3 is investigated. The nonlinear optical measurement shows that 3 displayed a second-harmonic-generation (SHG) response of 0.7 times that for urea.