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3 results on '"Co-aquo moiety"'

1. Water‐Assisted Concerted Proton‐Electron Transfer at Co(II)‐Aquo Sites in Polyoxotungstates With Photogenerated Ru III (bpy) 3 3+ Oxidant

Author

Nadia Marino, Marcella Bonchio, Mirco Natali, Antonio Marcomini, Andrea Sartorel, Alessandro Bonetto, and Francesco Rigodanza

Subjects
chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, Photochemistry, 01 natural sciences, Electron transfer, Reaction rate constant, flash photolysis, Co-aquo moiety, Reactivity (chemistry), Physical and Theoretical Chemistry, cobalt polyoxometalate, Aqueous solution, Hydrogen bond, hydrogen bonding, proton coupled electron transfer, Ambientale, 021001 nanoscience & nanotechnology, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, chemistry, Flash photolysis, Proton-coupled electron transfer, 0210 nano-technology, Cobalt
Abstract

The cobalt substituted polyoxotungstate [Co6 (H2 O)2 (α-B-PW9 O34 )2 (PW6 O26 )]17- (Co6) displays fast electron transfer (ET) kinetics to photogenerated RuIII (bpy)33+ , 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II)-OH2 and Co6(II)-OH, respectively, whose speciation in aqueous solution is associated to a pKa of 7.6), and generates a Co(III)-OH moiety (Co6(III)-OH), as proven by transient absorption spectroscopy; (ii) at pH>pKa , the Co6(II)-OH→RuIII (bpy)33+ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH

Published
2021
Full Text
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2. Water-Assisted Concerted Proton-Electron Transfer at Co(II)-Aquo Sites in Polyoxotungstates With Photogenerated Ru

Author

Francesco, Rigodanza, Nadia, Marino, Alessandro, Bonetto, Antonio, Marcomini, Marcella, Bonchio, Mirco, Natali, and Andrea, Sartorel

Subjects
Light, Polymers, Water, Electrons, Cobalt, Articles, Tungsten Compounds, Oxidants, hydrogen bonding, Ruthenium, Article, Kinetics, flash photolysis, Coordination Complexes, Very Important Paper, Organometallic Compounds, proton coupled electron transfer, Co-aquo moiety, Protons, Oxidation-Reduction, cobalt polyoxometalate
Abstract

The cobalt substituted polyoxotungstate [Co6(H2O)2(α‐B‐PW9O34)2(PW6O26)]17− (Co6) displays fast electron transfer (ET) kinetics to photogenerated RuIII(bpy)3 3+, 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one‐electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II)−OH2 and Co6(II)−OH, respectively, whose speciation in aqueous solution is associated to a pKa of 7.6), and generates a Co(III)−OH moiety (Co6(III)−OH), as proven by transient absorption spectroscopy; (ii) at pH>pKa, the Co6(II)−OH→RuIII(bpy)3 3+ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH, Kinetic investigation by laser flash photolysis supports the occurrence of a concerted proton electron transfer (CPET) from a CoII−OH2 unit embedded in a polyoxotungstate to photogenerated RuIII(bpy)3 3+, with water acting as the base within a hydrogen bonding network.

Published
2021

3. Water-Assisted Concerted Proton-Electron Transfer at Co(II)-Aquo Sites in Polyoxotungstates With Photogenerated Ru III (bpy) 3 3+ Oxidant.

Author

Rigodanza F, Marino N, Bonetto A, Marcomini A, Bonchio M, Natali M, and Sartorel A

Subjects
Cobalt chemistry, Coordination Complexes chemical synthesis, Kinetics, Light, Organometallic Compounds radiation effects, Oxidants chemistry, Oxidants radiation effects, Oxidation-Reduction, Polymers chemical synthesis, Ruthenium chemistry, Ruthenium radiation effects, Tungsten Compounds chemical synthesis, Water chemistry, Coordination Complexes chemistry, Electrons, Organometallic Compounds chemistry, Polymers chemistry, Protons, Tungsten Compounds chemistry
Abstract

The cobalt substituted polyoxotungstate [Co 6 (H 2 O) 2 (α-B-PW 9 O 34 ) 2 (PW 6 O 26 )] 17- (Co6) displays fast electron transfer (ET) kinetics to photogenerated Ru III (bpy) 3 3+ , 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II)-OH 2 and Co6(II)-OH, respectively, whose speciation in aqueous solution is associated to a pK a of 7.6), and generates a Co(III)-OH moiety (Co6(III)-OH), as proven by transient absorption spectroscopy; (ii) at pH>pK a , the Co6(II)-OH→Ru III (bpy) 3 3+ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH a , the process involves Co6(II)-OH 2 →Co6(III)-OH transformation and proceeds via a multiple-site, concerted proton electron transfer (CPET) where water assists the transfer of the proton, as proven by the absence of effect of buffer base concentrations on the rate of the ET and by a H/D kinetic isotope in a range of 1.2-1.4. The reactivity of water is ascribed to its organization on the surface of the polyanionic scaffold through hydrogen bond networking involving the Co(II)-OH 2 group., (© 2021 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Published
2021
Full Text
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