title: Reporting a unique example of electronic bistability observed in the form of valence tautomerism with a copper(II) helicate of a redox-active nitrogenous heterocyclic ligand.
abstract: Valence tautomeric compounds involving nondixolene-type ligands are rare. The triple-helicate copper(II) complex [Cu(II)(2)(L)(3)](ClO(4))(4)·3CH(3)CN (1) containing a redox-active N-heterocyclic ligand (L) has been prepared and displays VT equilibrium in solution, as established by electronic spectroscopy, electron paramagnetic resonance spectroscopy, and cyclic and differential pulse voltammetry carried out at variable temperatures. The process involves intramolecular transfer of an electron from one of the L ligands to a copper(II) center, leading to the oxidation of L to an L(•+) radical with concomitant reduction of the Cu(II) center to Cu(I), as shown by the equilibrium [Cu(II)Cu(I)L(•+)L(2)](4+) ⇄ [Cu(II)(2)L(3)](4+).
authors.affiliation: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India.
authors.forename: Nabanita
authors.initials: N
authors.lastname: Kundu
authors.forename: Manoranjan
authors.initials: M
authors.lastname: Maity
authors.forename: Pabitra Baran
authors.initials: PB
authors.lastname: Chatterjee
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Teat
authors.forename: Akira
authors.initials: A
authors.lastname: Endo
authors.forename: Muktimoy
authors.initials: M
authors.lastname: Chaudhury