Temperature-controlled assembly of three Cd(II)-coordination polymers based on 2′-carboxybiphenyl-4-ylmethylphosphonic acid and 1,10-phenanthroline

Abstract

Hydrothermal reactions of 2′-carboxybiphenyl-4-ylmethylphosphonic acid (H3L) with Cd(CH3COO)2·2H2O and 1,10-phenanthroline (phen) under different reaction temperatures afforded three new compounds, namely [Cd(phen)(HL)]·H2O (1), [Cd3(phen)4(L)2(H2O)]·9H2O (2) and [Cd4(phen)5(HL)(L)2]·2.5H2O (3). Compounds 1–3 have the same component but different structures. Compound 1 synthesized at 100 °C displays a one-dimensional chain structure containing mononuclear Cd. Compounds 2 and 3 formed at 160 °C exhibit one-dimensional chain structure containing trinuclear Cd unit and zero-dimensional structure containing hexanuclear Cd unit, respectively. The compounds have been characterized by elemental analyses, infrared spectra (IR), UV–vis spectra, single-crystal X-ray diffraction analyses and thermogravimetric analyses. The optical band gaps and photoluminescent properties of compounds 2 and 3 have been investigated. Three compounds have been synthesized with the same reactant ratio and solvent system by varying the reaction temperatures, where the effects of the reaction temperatures on the structures have been discussed. Moreover, the optical band gaps and photoluminescent properties have also been studied.