Two new series of each of four Cr(III) and Ni(II) imino nitroxide complexes with various kinds of β-diketonates, [Cr(β-diketonato)2(IM2py)]PF6, and [Ni(β-diketonato)2(IM2py)] (IM2py = 2-(2′-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy)) have been synthesized, and their structures and magnetic and optical properties have been examined. The X-ray analysis demonstrated that a IM2py ligand coordinated to Cr(III) and Ni(II) acts as a five-membered bidentate chelate. The variable-temperature magnetic susceptibility measurements indicated the antiferromagnetic and ferromagnetic interaction of Cr(III) and Ni(II) with IM2py, respectively, giving a variety of the magnetic coupling constant J values with varying the β-diketonato ligands. The UV-vis shoulders around (19-20) x 103 and (17-18) x 103 cm-1 for the Cr(III) and Ni(II) complexes, respectively, characteristic of the IM2py complexes were assigned to the metal-ligand charge-transfer transitions, Cr(t2g)-SOMO(π*) and Ni(eg)-SOMO(π*) MLCT in terms of the resonance Raman spectra and the variable-temperature absorption spectra. The absorption components centered around (13-14) x 103 cm-1 for the Cr(III) and Ni(II) complexes were due to the formally spin-forbidden d-d transition within the t2g and eg subshells, associated with the intensity enhancement. The spectroscopic behavior with varying the β-diketonato ligands is discussed in connection with the antiferromagnetic or ferromagnetic coupling constant J values on the basis of the exchange mechanism along with the coligand effect.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry