Doubly mononuclear cocrystal and oxalato-bridged binuclear copper compounds containing flexible 2-((3,5,6-trichloropyridin-2-yl)oxy)acetate tectons: Synthesis, crystal analysis and magnetic properties

Two new copper compounds, namely [Cu(3,5,6-tcpa)2(H2O)(4)]center dot[Cu(3,5,6-tcpa)(2)(H2O)(2)] (1) and [Cu-2(3,5,6-tcpa)(2)(2,2'-bipy)(2)(oxa)]center dot 2EtOH (2) (3,5,6-Htcpa = 2-((3,5,6-trichloro pyridin-2-yl)oxy)acetic acid, 2,2 '- bipy = 2,2'-bipyridine, oxa = oxalate dianion), have been synthesized by solvothermal method and system-atically characterized. Single-crystal X-ray diffraction analysis show that 1 is an interesting double mononuclear cocrystal and consists of two discrete and stereochemically different complexes: one octahedral, the other tet-rahedral about the copper centres. While for 2, two equivalent copper ions are in square pyramidal geometry and linked by oxalate anion forming a novel binuclear cluster. The OeH center dot center dot center dot O hydrogen bonds, Cl center dot center dot center dot Cl halogen bonds and/or pi center dot center dot center dot pi stacking interactions play an important part in construction of the 3D networks for 1 and 2. The magnetic measurements indicate that there is weak antiferromagnetic coupling between two copper ions in 1 and 2. Notably, compound 2 also can be obtained in a higher yield with 1 as one of the starting material and the driving force for this transition process have been carefully discussed.