Water-sulfate anion interplay in the evolution of solid state architectures and emission properties of Zn and Cd coordination networks with four azine ligands

Abstract

Reactions of zinc and cadmium sulfates with 1,2-bis(pyridin-3-ylmethylene)hydrazine (3-bphz), 1,2-bis(pyridin-4-ylmethylene)hydrazine (4-bphz), and two methylated derivatives, 1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine (3-bpmhz) and 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine (4-bpmhz) resulted in eight coordination compounds. For Zn(II) the structural landscape includes binuclear complexes and two-dimensional coordination polymers, [Zn2(3-bphz)(H2O)10](SO4)2.4H2O (1), [Zn2(SO4)2(3-bphz)(H2O)4]n (2), [Zn2(3-bpmhz)3(H2O)8](SO4)2 (3), and {[Zn(SO4)(4-bpmhz)(H2O)2].1.5(H2O)·0.25(4-bpmhz)}n (4). For Cd(II) two- and three-dimensional coordination networks, {[Cd(SO4)(4-bpmhz)(H2O)1.32]·1.2(H2O)}n (5), [Cd(SO4)(3-bpmhz)(H2O)]n (6), {[Cd(SO4)(4-bphz)(H2O)]·(H2O.C2H5OH)}n (7), and [Cd3(SO4)3(3-bphz)3(H2O)2]n (8) are reported. The extension of crystal structures up to two- and three-dimensional coordination networks has been achieved via bidentate bridging neutral azine ligands, and bi- and tridentate bridging sulfate anions that provide the metal-sulfate inorganic scaffolds in the forms of different one- and two-dimensional coordination arrays. The new crystalline solids were studied by X-ray single crystal and powder diffraction, spectroscopic and thermogravimetric analytical methods. The water-sulfate-anion interplay, similarities and dissimilarities in the coordination networks' topologies, the inherent chiralities of coordination networks, an impact of ligands’ methylation on solvent uptake, and the emission events accompanying the thermal stress are demonstrated and discussed.