The effect of electronic structure on electrocatalytic behaviors of cobalt Schiff base complexes: Electrosynthesis of 2-phenylacetic acid using carbon dioxide

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2014-10, Vol.732, p.117-121
• Main Authors: Khoshro, Hossein, Zare, Hamid R., Gorji, Alireza, Namazian, Mansoor, Jafari, Abbas A., Vafazadeh, Rasoul
• Format: Article
• Language: English
• Subjects: 2-Phenylacetic acid; Benzyl bromide; CO2 fixation; Cobalt complexes; DFT
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2014.07.039

[Display omitted] •The electrochemical carboxylation of benzyl bromide was catalyzed using two cobalt complexes.•Mechanism of the carboxylation of benzyl bromide is depending on the electronic structure of the complexes.•Phenyl acetic acid is the final product of electrocatalytic reduction of benzyl bromide in the presence of CO2.•The presence of CO2 improves the catalytic efficiency and stability of the complexes. Electrochemical fixation of carbon dioxide was used as an efficient method to synthesize 2-phenylacetic acid. The electrochemical carboxylation of benzyl bromide by two cobalt Schiff base complexes of [N,N′-bis(salicylaldehyde)-1,2-phenylenediimino cobalt(II)], [Co(II) salophen], and [N,N′-bis(benzoylacetone) ethylenediimino cobalt(II)], [Co(II) bzaen], in N,N-dimethylformamide and in the presence of carbon dioxide was investigated using cyclic voltammetry method. The electrocatalytic reduction mechanism of benzyl bromide is dependent on the electronic structure of the complexes. Moreover, the presence of CO2 improves the catalytic efficiency and stability of the complexes. Finally, controlled potential coulometry (CPC) and constant current coulometry (CCC) were carried out in the absence and the presence of CO2. The electrosynthesis yields of 2-phenylacetic acid from benzyl bromide are obtained by 50% and 55% using CPC and 60% and 70% using CCC under mild conditions using [Co(II) salophen] and [Co(II) bzaen] complexes respectively. DFT calculations along with Mulliken/NBO studies have been carried out, in order to support the experimental results.