Three novel transition metal coordination polymers based on (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid sodium salt: Hydrothermal syntheses, structures, and properties

Abstract

Three novel transition metal coordination polymers including [Cd2(Na2PPDA)2Cl4]n (I), [Zn(Na2PPDA)(ClO4)2·4H2O]n (II) and [Ni(Na2PPDA)(ClO4)2·4H2O]n (III) were prepared under hydrothermal conditions based on (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic acid sodium salt (Na2PPDA) and characterized by elemental analysis, infrared spectrometry and single crystal X-ray diffraction. The outstanding structural feature of I is that four cadmium atoms are linked into a zigzag-shaped polymeric chain in the sequence of Cd–(Cl)2–Cd–(Cl)2–Cd–(Cl)2–Cd by three μ2-Cl bridges. Findings indicate that I displays a three-dimensional (3D) network constructed via hydrogen bonds and C–H⋯π interactions. Both coordination polymers of II and III present isomorphous and isostructural characters, in which the adjacent metal centers in the same chain connected up and down through hydrogen bonds (generated through μ2-ClO4− anions) to construct the left- and right-handed helical chains which are further interconnected by hydrogen bonds, thereby affording a two-dimensional (2D) layer. Moreover, thermogravimetric (TG) analyses, the magnetic and luminescent properties of as-synthesized coordination polymers were also investigated.