Pentacoordinate Co(II) complex based on bulky tridentate and bidentate ligands with field-supported slow magnetic relaxation

Abstract Reaction of cobalt(II) acetate with neocuproine ( neoc , 2,9-dimethyl-1,10-phenantroline) and Schiff base H 2 ( samphe ) (Schiff base formed by condensation of salicylaldehyde with 2-amino-4-methylphenol) afforded complex [Co( neoc )( samphe )] ( 1 ) which was chemically and spectroscopically characterized. Crystal structure of 1 is composed of neutral complex molecules in which the Co(II) atom is pentacoordinated and its coordination sphere is formed by one chelating neoc ligand and one tridentate dianionic chelating ligand samphe 2- (ONO-donor). Calculated τ 5 value of 0.435 indicates that the coordination polyhedron can be viewed as an intermediate shape between a square pyramid and a trigonal bipyramid. The complex 1 displays enhanced thermal stability up to 330 °C. The magnetic study of 1 has shown that Co(II) is in a high-spin state S = 3/2 and exhibits easy-axis magnetic anisotropy with parameters D = -48.7 cm -1 and E/D = 0.166. The AC magnetic study indicates the presence of field-supported slow magnetic relaxation with a maximum of the imaginary component above 10 kHz. The results of the magnetic study are supported by theoretical calculations. Graphical abstract