Charge distribution in bis-dioxolene radical metal complexes. Synthesis and DFT characterization of dinuclear Co(III) and Cr(III) complexes with a mixed-valent, S=1/2 semiquinone-catecholate ligand
A. Bencini et al., Charge distribution in bis-dioxolene radical metal complexes. Synthesis and DFT characterization of dinuclear Co(III) and Cr(III) complexes with a mixed-valent, S=1/2 semiquinone-catecholate ligand, INORG CHEM, 40(7), 2001, pp. 1582-1590
Bis-dioxolene bridged dinuclear metal complexes of general formula M-2(CTH)
(2)(diox-diox)(PF6)(n) (n = 2, 3; M = Co(III), Cr(III); CTH = tetraazamacro
cycle) have been synthesized using the bis-bidentate ligand 5,5'-di-tert-bu
tyl-3,3',3,4'-tetrahydroxybiphenyl. These complexes were characterized by m
eans of ESR, UV-vis, temperature dependent magnetic susceptibility,and cycl
ic voltammetry. Our results unambiguously suggest that the tripositive dime
tal cations can be described as containing a fully delocalized bis-dioxolen
e trinegative radical ligand (Cat-Sq) bridging two tripositive metal cation
s. In this frame the sextet electronic ground state characterizes the Cr-2(
CTH)(2)(Cat-SQ)(3+) as a result of the antiferromagnetic coupling of the ra
dical bridging ligand with the two equivalent paramagnetic metal centers. T
he electronic and geometrical structure: and the magnetic properties of Cat
-Sq and of its complexes have been studied with density functional theory.