Synthesis of new photosensitive H2BBQ2+[ZnCl4]2-/[(ZnCl)2(μ-BBH)] complexes, through selective oxidation of H2O to H2O2

M Stylianou; I Hadjiadamou; C Drouza; S C Hayes; E Lariou; I Tantis; P Lianos; A C Tsipis; A D Keramidas

doi:10.1039/c6dt04643f

Synthesis of new photosensitive H₂BBQ²⁺[ZnCl₄]^2-/[(ZnCl)₂(μ-BBH)] complexes, through selective oxidation of H₂O to H₂O₂

Dalton Trans. 2017 Mar 14;46(11):3688-3699. doi: 10.1039/c6dt04643f.

Authors

M Stylianou¹, I Hadjiadamou², C Drouza³, S C Hayes², E Lariou², I Tantis⁴, P Lianos⁴, A C Tsipis⁵, A D Keramidas²

Affiliations

¹ Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus. akeramid@ucy.ac.cy shayes@ucy.ac.cy and Department of Agricultural Production Biotechnology and Food Science, Cyprus University of Technology, Limassol 3036, Cyprus. chryssoula.drouza@cut.ac.cy.
² Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus. akeramid@ucy.ac.cy shayes@ucy.ac.cy.
³ Department of Agricultural Production Biotechnology and Food Science, Cyprus University of Technology, Limassol 3036, Cyprus. chryssoula.drouza@cut.ac.cy.
⁴ Department of Chemical Engineering, University of Patras, 26500 Patras, Greece. lianos@upatras.gr.
⁵ Laboratory of Inorganic and General Chemistry, University of Ioannina, 45110 Ioannina, Greece. attsipis@uoi.gr.

PMID: 28256650
DOI: 10.1039/c6dt04643f

Abstract

A new two-electron photosensitizer, H₂BBQ²⁺[ZnCl₄]^2-/[(ZnCl)₂(μ-BBH)] (BBQ stands for 2,5-bis[bis(pyridin-2-ylmethyl)amino]-1,4-quinone and BBH stands for 2,5-bis[bis(pyridin-2-ylmethyl)amino]-1,4-hydroquinone), has been synthesized and the oxidation state of the ligand was determined by X-ray crystallography and NMR spectroscopy. Under light illumination the H₂BBQ²⁺[ZnCl₄]^2- + ZnCl₂ is reduced quantitatively to [(ZnCl)₂(μ-BBH)] (pH ∼ 5) oxidizing H₂O to H₂O₂ as is evident by trap experiments. Electrochemistry gave a reversible two-electron ligand-centered redox wave for [(ZnCl)₂(μ-BBH)]. UV-Vis, luminescence and EPR spectroscopies reveal the slow formation of a stable quinone diradical, intermediate of the reaction. DFT calculations are in agreement with the proposed mechanism. Based on this property an aqueous {[(ZnCl)₂(μ-BBH)]||H₂O₂} solar rechargeable galvanic cell has been constructed.