New trinuclear metal string complexes containing rigid Hdzp ligands: synthesis, structure, magnetism and DFT calculation (Hdzp = 1,9-diazaphenoxazine)

The synthesis, crystal structure, magnetic properties, and single-molecule conductance of two new trinuclear metal string complexes, [Ni3(dzp)4(NCS)2] (2) and [Co3(dzp)4(NCS)2] (3), containing the rigid Hdzp ligand (1, 1,9-diazaphenoxazine) are reported. X-ray structural analyses show that compounds 2 and 3 exhibit smaller torsion angles and longer metal–metal distances than those exhibited by the corresponding dpa− analogues (dpa− = dipyridylamido anion) due to the rigidity of Hdzp ligands. The longer metal–metal distance observed for 2 and 3 results in variations in their magnetic properties. The exchange interaction (J = −160 cm−1) between two high spin (HS) Ni(II) ions in 2 decreases slightly in comparison with those of trinickel dpa− analogues. The doublet–quartet gap of 3 is smaller than that of [Co3(dpa)4(NCS)2] (4), which causes compound 3 to show spin-crossover behavior even at low temperature.