One-pot solvothermal synthesis of mononuclear and oxalate-bridged binuclear nickel compounds: Structural analyses, conformation alteration and magnetic properties

Two new discrete compounds with the formula [Ni(3,5,6-tcpa)(2,2 & PRIME;-bipy)Cl] (1) and [Ni-2(3,5,6-tcpa)(2)(2,2 & PRIME;- bipy)(2)(ox)].2EtOH (2) (3,5,6-Htcpa = 2-((3,5,6-trichloro pyridin-2-yl)oxy)acetic acid, 2,2 & PRIME;-bipy = 2,2 & PRIME;-bipyridine, ox = oxalate dianion) have been co-synthesized under solvothermal conditions in the same medium. Single-crystal X-ray diffraction analysis shows that both 1 and 2 have crystallized in triclinic system, space group P(1) over bar and the central Ni-II ions are both in deformed square-pyramids. The Ni-II ion in 1 was bonded by one chloride ion (Cl-), one bidentate chelate 3,5,6-tcpa anion and one 2,2 & PRIME;-bipy to give a mononuclear complex 1. While for 2, the Ni-II ion was coodinated with one monodentate 3,5,6-tcpa, one oxalate anion and one 2,2 & PRIME;-bipy. The oxalate anion linked two equivalent NiII ions to form the binuclear cluster 2. The Cl...Cl halogen bonds, pi...pi stacking interactions and/or O-H...O hydrogen bonds play an important part in the crystal packing for 1 and 2. Their deeply structural analyses revealed that the similar structure features and conformation alteration of 3,5,6-tcpa may be responsible for the cocrystallization phenomenon of 1 and 2. The magnetic measurements indicated the presence of intramolecular weak ferromagnetic coupling with J = 1.02 cm(-1) in 2.