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

Abstract

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.