Syntheses, structures and properties of four Cd(II) coordination polymers induced by the pH regulator

Four new coordination polymers [Cd-2(CHDC)(2)(APYZ)(H2O)(2)](H2O) (1), [Cd(HCHDC)(2)(APYZ) (H2O)] (2), [Cd-2(CHDC)(2)(PYZ)(H2O)(2)](H2O) (3), and [Cd(HCHDC)(2)(PYZ)(H2O)] (4) (H2CHDC = 1,4-cyclohexanedicarboxylic acid, APYZ = 2-aminopyrazine, PYZ = pyrazine) have been synthesized under the hydrothermal conditions by changing the pH regulator and the N-containing ligands. The pH regulator impacted on the degree of deprotonation of the 1,4-cyclohexanedicarboxylic acid ligand and resulted in the formation of the two pairs of different networks. Polymers 1 and 3 crystallize in monoclinic, space group P2(1)/c, exhibit two dimensional 63 net, which further formed threedimensional supramolecular structure by the C-H...O hydrogen bond interactions. While polymers 2 and 4 possess one dimensional chain structures and further link into two dimensional layered supramolecular structures by intermolecular hydrogen bonding interactions. From all three conformers of H2CHDC, e,a-cis is consistently present in the Cd coordination polymers. Furthermore, photoluminescence properties of four polymers are also investigated, the luminescent intensity of polymer (or 2) with amino group in pyrazine is dramatically stronger than that of the similar structure of polymer 3 (or 4) without amino group in pyrazine, the results shown that the presence of the amino group from 2-aminopyrazine play a key role in increasing the luminescence properties. (C) 2017 Elsevier B.V. All rights reserved.