Diaquabis(2,2'-dipyridylamine) M(II) Terephthalate Dihydrates, M(II) = Ni, Co: Synthesis, Crystal Structures, Thermal and Magnetic Properties

Abstract

Two new isostructural M(II) (M = Ni, Co) complexes with 2,2'-dipyridylamine (dipya) and dianion of terephthalic acid (H-2 tpht), [M(dipya) (2)(H2O)(2)](tpht) center dot 2H(2)O, have been synthesized by ligand exchange reaction and characterized by single-crystal X-ray diffraction, FTIR spectroscopy, TG/DSC analysis and magnetic measurements. The crystal structures of [M(dipya)(2)(H2O)(2)](tpht) center dot 2H(2)O consist of discrete complex units in which M(II) adopts deformed octahedral geometries. Two dipya ligands and two water molecules are coordinated to M(II) atom, tpht acts as a counter ion, while additional two water molecules remained uncoordinated. By numerous hydrogen bonds, all structural fragments are connected in three different chains which extend along [100], [010] and [001] directions, giving as a result a complex 3D network. The stabilization of 3D structure is accomplished by non-covalent face to face pi-pi interactions among pyridyl ring of dipya and benzene ring of tpht from adjacent chains. Towards the applied magnetic field, the both complexes exhibited almost perfect paramagnetic behavior.