title: Syntheses, crystal structures, and spectroscopic and magnetic properties of [Mn2III(H2L1)(Cl4Cat)4.2H2O] and [Mn2III(H2L2)(Cl4Cat)4.2CH3CN.2H2O]infinity: temperature-dependent valence tautomerism in solution.
abstract: The synthesis, X-ray data, and electronic structures of two manganese(III) 1D polymers ligated by tetrachlorocatechol, [Mn(2)(III)(H(2)L(1))(Cl(4)Cat)(4).2H(2)O](infinity) (1) and [Mn(2)(III)(H(2)L(2))(Cl(4)Cat)(4).2CH(3)CN.2H(2)O](infinity) (2), are reported. The electronic structures of the complexes have been determined by UV-vis-near-IR, IR, electron paramagnetic resonance (EPR), and magnetic susceptibility measurements. Both 1 and 2 are air stable in the solid state and in solution, unlike most of the previously reported o-quinone-chelated transition-metal complexes. Electronic spectroscopy exhibits a strong near-IR band near 1900 nm for both, suggesting the presence of a mixed-valence semiquinone-catecholate oxidation state of the catechol ligands, Mn(2)(III)(Cl(4)Cat)(2)(Cl(4)SQ)(2), together with the pure catecholate forms. The presence of this isomer was further supported by EPR and magnetic susceptibility measurements. The complexes undergo intramolecular electron transfer (valence tautomerism) upon an increase of the temperature involving the equilibrium Mn(2)(III)(Cl(4)Cat)(2)(Cl(4)SQ)(2) <==> Mn(2)(II)(Cl(4)SQ)(4). This phenomenon is reversible and is studied in solution using UV-vis-near-IR spectroscopy.
authors.affiliation: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India.
authors.forename: Nizamuddin
authors.initials: N
authors.lastname: Shaikh
authors.forename: Sanchita
authors.initials: S
authors.lastname: Goswami
authors.forename: Anangamohan
authors.initials: A
authors.lastname: Panja
authors.forename: Hao-Ling
authors.initials: HL
authors.lastname: Sun
authors.forename: Feng
authors.initials: F
authors.lastname: Pan
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Pradyot
authors.initials: P
authors.lastname: Banerjee