Structure, photochemistry and magnetic properties of tetrahydrogenated Schiff base chromium(III) complexes

Abstract

Four mononuclear chromium(III) complexes [Cr(L(1))(en)]Br0.3Cl0.7 (1), [Cr(L(1))(pr)]Cl (2), [Cr(L(2))(en)]ClO4 (3), [Cr(L(2))(pr)]Cl (4) along with one dinuclear μ-methoxo [Cr(μ-OMe)(L1)]2 (5) were synthesized (en=1,2-ethanediamine, pr=1,3-diaminopropane H2L(1)=Tetrahydrosalen=H2[H4]salen=N,N'-bis(2-hydroxybenzyl)-1,2-ethanediamine, H2L(2)=Tetrahydrosalpr=H2[H4]salpr=N,N'-bis(2-hydroxybenzyl)-1,3-diaminopropane). The competitive reactions in the presence of EDTA were carried out and the first-order rate constants k(1)=(5.2±0.2)×10(-3) h(-1)<k(2)=(6.7±0.3)×10(-3) h(-1)<k(3)=(8.0±0.1)×10(-3) h(-1)<k(4)=(9.5±0.2)×10(-3) h(-1) were obtained by spectroscopic measurements. In addition, photo-induced decomposition was monitored under irradiation of xenon lamp. The sequence of first-order rate constants is k'(1)=(4±0.1)×10(-4) s(-1)<k'(2)=(6±0.3)×10(-4) s(-1)<k'(3)=(1.1±0.2)×10(-3) s(-1)<k'(4)=(1.4±0.2)×10(-3) s(-1), which is in accordance with that of kinetics studies with EDTA. Dinuclear complex 5 exhibits a strong antiferromagnetic coupling with the J=-10.8 cm(-1).

Keywords: Chelate effect; Chromium(III); Kinetics; Magnetism; Photochemistry; Tetrahydrogenated Schiff base.