Studies on complexes containing mixed-valence semiquinone-catecholate ligands. Synthesis and characterization of bis(o-quinone)(bipyridine)chromium(III) complexes

Synthesis, X-structure and solvent induced electronic states tuning of meso-tris(4-nitrophenyl)corrolato-copper complex

“…Thus, although +3 oxidation state of Cu is stable in nonpolar solvent, intramolecular electron transfer facilitated by polar medium (by favorable mixing of the d-orbitals of metal ion with the orbital of the corrole ring) made Cu(II)-corrole 2ÅÀ state to be stable in the polar solvent. [44][45][46][47][48].…”

Kinetics and mechanism of the reaction between chromium(III) and 3,4-dihydroxyphenylpropionic (dihydrocaffeic) acid in weak acidic aqueous solutions

“…In these cases the redox activity involves the ligands rather than the chromium ion. The synthesis and characterisation of bis(o-quinone)(bipyridine)chromium(III) complexes have been described [11], where the metal ion, chromium(III), is kinetically stable and not directly involved in the redox activity. Dissociation becomes significant only when the ligands are in a fully oxidized benzoquinone form [11].…”

“…The synthesis and characterisation of bis(o-quinone)(bipyridine)chromium(III) complexes have been described [11], where the metal ion, chromium(III), is kinetically stable and not directly involved in the redox activity. Dissociation becomes significant only when the ligands are in a fully oxidized benzoquinone form [11]. Studies on complexes containing mixed-valence semiquinone-catecholate ligands have also been reported [11].…”

“…Dissociation becomes significant only when the ligands are in a fully oxidized benzoquinone form [11]. Studies on complexes containing mixed-valence semiquinone-catecholate ligands have also been reported [11].…”

“…If oxidation of the ligand had taken place, charge-transfer bands with high intensities should be observed. It is very well established that the electronic spectra of complexes of the Cr(semiquinone) 3 and Cr(quinone) 2 (bpy) series are dominated by the charge-transfer bands with high-intensities [11] and it has been reported that the most prominent features of the spectra in both the above cases are the bands in the 500 nm region [11]. Such bands have not been observed in the present study, in the spectra of the complexes of dihydrocaffeic acid with Cr(III) under weak acidic conditions (Fig.…”