Synthesis of a series of coordination polymers based on mixed ligands to tune the structural dimension

Abstract

Eight coordination polymers, namely, Mn(cob)(phen) (1), Co(cob)(phen)₂(H₂O)·5H₂O (2), Co(cob)(phen) (3), Cd(cob)(phen) (4), Mn(cob)(bpy)(H₂O)₂ (5), Co(cob)(bpy)(H₂O)₂ (6), Cu(Hcob)₂(bpy)(H₂O)₂·H₂O (7), Cd(cob)(bpy) (8) (H₂cob = 2-[(4′-carboxybenzyl)oxy]benzoic acid, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) have been synthesized under hydrothermal conditions by H₂cob, different N-donor ligands and transition metal salts. These eight complexes have been characterized by elemental analysis, infrared (IR) spectroscopy, thermogravimetric analysis (TGA), and single-crystal X-ray diffraction. Complexes 1, 3 and 4 are isostructural and feature two-dimensional (2D) wave-like layer networks, which are further interconnected by inter-layer π⋯π stacking interactions to form three-dimensional (3D) supramolecular structures. Complexes 2 and 7 are both mononuclear structures which are further self-assembled through hydrogen bonding and π⋯π stacking interactions to generate 3D supramolecular structures. Complexes 5 and 6 are isostructural and show one-dimensional (1D) zigzag chains, which are further connected by hydrogen bonding to form a 2D supramolecular structure. Complex 8 is an infinite 1D linear structure. Desorption of lattice water molecules in complexes 2, 5 and 6 was analyzed, and demonstrates that these water molecules may influence the construction of the final structures. The water sorption studies reveal that complexes 2, 5 and 6 exhibit good water vapor uptake (64.12 ml g⁻¹ for 2, 40.26 ml g⁻¹ for 5 and 55.34 ml g⁻¹ for 6). Furthermore, the fluorescence properties of 1–8 have been investigated. Magnetic susceptibility measurements indicate that complexes 1–3 show weak antiferromagnetic behavior, while 5–6 exhibit ferromagnetic behavior.