One Electron Reduced Square Planar Bis(benzene-1,2-dithiolato) Copper Dianionic Complex and Redox Switch by O2/HO-

Biplab Kumar Maiti, Luísa Bernardina Lopes Maia, Kuntal Pal, Bholanath Pakhira, Maria Teresa Avilés, Isabel Maria Andrade Martins Galhardas de Moura, Sofia Rocha Pauleta, Jose L. Nunez, Alberto C. Rizzi, Carlos D. Brondino, Sabyasachi Sarkar, José João Galhardas de Moura

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Abstract

The complex [Ph4P](2)[Cu(bdt)(2)] (1(red)) was synthesized by the reaction of [Ph4P]2[S2MoS2CuCl] with H2bdt (bdt = benzene-1,2-dithiolate) in basic medium. 1(red) is highly susceptible toward dioxygen, affording the one electron oxidized diamagnetic compound [Ph4P][Cu(bdt)(2)] (1(ox)). The interconversion between these two oxidation states can be switched by addition of O-2 or base (Et4NOH = tetraethylammonium hydroxide), as demonstrated by cyclic voltammetry and UV-visible and EPR spectroscopies. Thiomolybdates, in free or complex forms with copper ions, play an important role in the stability of 1(red) during its synthesis, since in its absence, 1(ox) is isolated. Both 1(red) and 1(ox) were structurally characterized by X-ray crystallography. EPR experiments showed that 1(red) is a Cu(II)-sulfur complex and revealed strong covalency on the copper-sulfur bonds. DFT calculations confirmed the spin density delocalization over the four sulfur atoms (76%) and copper (24%) atom, suggesting that 1(red) has a "thiyl radical character". Time dependent DFT calculations identified such ligand to ligand charge transfer transitions. Accordingly, 1(red) is better described by the two isoelectronic structures [Cu(I)(bdt(2), 4S(3-*))](2-) [Cu-II(bdt(2), 4S(4-))](2-). On thermodynamic grounds, oxidation of 1(red) (doublet state) leads to 1(ox) singlet state, [Cu-III(bd(t)2, 4S(4-))](1-).
Original languageEnglish
Pages (from-to)12799-12808
JournalInorganic Chemistry
Volume53
Issue number24
DOIs
Publication statusPublished - 15 Dec 2014

Keywords

  • PARAMAGNETIC RESONANCE-SPECTRA
  • RAY-ABSORPTION SPECTROSCOPY
  • EFFECTIVE CORE POTENTIALS
  • SINGLE-CRYSTAL EPR
  • DITHIOLENE COMPLEXES
  • SPIN RESONANCE
  • ORANGE PROTEIN
  • AB-INITIO
  • ELECTROCATALYTIC REDUCTION
  • MOLECULAR CALCULATIONS

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