A dicobalt(III) complex containing triple helical N-N bridges: Synthesis, structure and property

A new dinuclear cobalt(III) complex, [Co₂L₃] ·8H₂O (1), (H₂L=N,N′-bis (2-picolinoyl)hydrazine), was synthesized by a hydrothermal method and characterized by UV, FT-IR, ESI-MS, TGA, EA and single crystal X-ray crystallography. The complex crystallizes in trigonal system with space group R3̄c, a=1.636 40(11) nm, α=48.52°, V=2.255 6 (3) nm³,Z=2, and final R=0.062. Each Co(III) has an octahedral [CoN₆] core. Each L^2- ligand binds simultaneously to two Co(III) cations in a bis(N,N′)-bridging coordination mode with a Co···Co distance of 0.349 7(2) nm. The hydrogen bonding interactions between carbonyl group and pyridyl ring link the molecules of into a 1D chain which was further connected by the lattice water to form a 3D supramolecular framework. The TG analysis shows that 1 loses lattice water at 90°C and is stable below 500°C. Magnetic measurement reveals that 1 is a low-spin species in the range of 1.8~375 K. CCDC: 744616.