Synthesis, structural characterization, and electrocatalytic hydrogen generation activity of fac-tris(β-oxodithioester-O^S)cobalt(iii) complexes
(2026) In Dalton Transactions 55(20). p.7955-7969- Abstract
With growing interest in cobalt-based complexes for electrocatalytic applications, we synthesized four homoleptic facial-octahedral Co(iii) β-oxodithioester complexes (1–4) with the general composition [Co(L)3], where L represents 3-(methylthio)-1-(furan-2-yl)-3-thioxoprop-1-en-1-olate (L1), 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate (L2), 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate (L3), and 3-(methylthio)-1-phenyl-3-thioxoprop-1-en-1-olate (L4). The complexes were fully characterized using elemental analysis, FTIR, UV-Vis, 1H and 13C{1H} NMR spectroscopy. Single-crystal X-ray diffraction confirmed a distorted octahedral geometry around each cobalt center, with... (More)
With growing interest in cobalt-based complexes for electrocatalytic applications, we synthesized four homoleptic facial-octahedral Co(iii) β-oxodithioester complexes (1–4) with the general composition [Co(L)3], where L represents 3-(methylthio)-1-(furan-2-yl)-3-thioxoprop-1-en-1-olate (L1), 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate (L2), 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate (L3), and 3-(methylthio)-1-phenyl-3-thioxoprop-1-en-1-olate (L4). The complexes were fully characterized using elemental analysis, FTIR, UV-Vis, 1H and 13C{1H} NMR spectroscopy. Single-crystal X-ray diffraction confirmed a distorted octahedral geometry around each cobalt center, with three ligands coordinated in an O^S-chelating mode. Complexes were evaluated for their electrocatalytic activity towards proton reduction. Electrochemical studies were carried out in dimethylformamide (DMF) with trifluoroacetic acid (TFA) serving as the proton donor. The findings indicated that all complexes exhibit electrocatalytic hydrogen evolution activity. Notably, complex 1 demonstrates superior catalytic activity among the four complexes, achieving an overpotential of 580 mV, high turnover frequencies (∼103 s−1) and faradaic efficiency (89%). The UV-Vis spectral and rinse test studies together with controlled potential electrolysis (CPE) indicated that all complexes are stable under acidic conditions, maintaining their molecular integrity throughout the catalytic process. Furthermore, computational and spectroelectrochemical studies support an ECEC mechanism for proton reduction by β-oxodithioester cobalt complexes, where the second protonation step is rate-determining. This is also supported by foot-of-the-wave analysis (FOWA) with the second protonation step as a rate-determining step (k1 > k2). This step generates a Co(ii)–H intermediate, which subsequently leads to hydrogen evolution.
(Less)
- author
- Mishra, Anjali ; Yadav, Chote Lal ; Yi, Jun ; Lisensky, George ; Drew, Michael G.B. ; Mishra, Gaurav Kumar ; Ding, Wendu ; Nordlander, Ebbe LU ; Singh, Nanhai and Kumar, Kamlesh
- organization
- publishing date
- 2026-05-26
- type
- Contribution to journal
- publication status
- published
- in
- Dalton Transactions
- volume
- 55
- issue
- 20
- pages
- 15 pages
- publisher
- Royal Society of Chemistry
- external identifiers
-
- pmid:42093456
- scopus:105037927940
- ISSN
- 1477-9226
- DOI
- 10.1039/d5dt02726h
- language
- English
- LU publication?
- yes
- id
- e68eb426-ddc3-4855-83a9-443d27ceec7a
- date added to LUP
- 2026-07-08 11:24:47
- date last changed
- 2026-07-08 11:25:49
@article{e68eb426-ddc3-4855-83a9-443d27ceec7a,
abstract = {{<p>With growing interest in cobalt-based complexes for electrocatalytic applications, we synthesized four homoleptic facial-octahedral Co(iii) β-oxodithioester complexes (1–4) with the general composition [Co(L)<sub>3</sub>], where L represents 3-(methylthio)-1-(furan-2-yl)-3-thioxoprop-1-en-1-olate (L1), 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate (L2), 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate (L3), and 3-(methylthio)-1-phenyl-3-thioxoprop-1-en-1-olate (L4). The complexes were fully characterized using elemental analysis, FTIR, UV-Vis, <sup>1</sup>H and <sup>13</sup>C{<sup>1</sup>H} NMR spectroscopy. Single-crystal X-ray diffraction confirmed a distorted octahedral geometry around each cobalt center, with three ligands coordinated in an O^S-chelating mode. Complexes were evaluated for their electrocatalytic activity towards proton reduction. Electrochemical studies were carried out in dimethylformamide (DMF) with trifluoroacetic acid (TFA) serving as the proton donor. The findings indicated that all complexes exhibit electrocatalytic hydrogen evolution activity. Notably, complex 1 demonstrates superior catalytic activity among the four complexes, achieving an overpotential of 580 mV, high turnover frequencies (∼10<sup>3</sup> s<sup>−1</sup>) and faradaic efficiency (89%). The UV-Vis spectral and rinse test studies together with controlled potential electrolysis (CPE) indicated that all complexes are stable under acidic conditions, maintaining their molecular integrity throughout the catalytic process. Furthermore, computational and spectroelectrochemical studies support an ECEC mechanism for proton reduction by β-oxodithioester cobalt complexes, where the second protonation step is rate-determining. This is also supported by foot-of-the-wave analysis (FOWA) with the second protonation step as a rate-determining step (k<sub>1</sub> > k<sub>2</sub>). This step generates a Co(ii)–H intermediate, which subsequently leads to hydrogen evolution.</p>}},
author = {{Mishra, Anjali and Yadav, Chote Lal and Yi, Jun and Lisensky, George and Drew, Michael G.B. and Mishra, Gaurav Kumar and Ding, Wendu and Nordlander, Ebbe and Singh, Nanhai and Kumar, Kamlesh}},
issn = {{1477-9226}},
language = {{eng}},
month = {{05}},
number = {{20}},
pages = {{7955--7969}},
publisher = {{Royal Society of Chemistry}},
series = {{Dalton Transactions}},
title = {{Synthesis, structural characterization, and electrocatalytic hydrogen generation activity of fac-tris(β-oxodithioester-O^S)cobalt(iii) complexes}},
url = {{http://dx.doi.org/10.1039/d5dt02726h}},
doi = {{10.1039/d5dt02726h}},
volume = {{55}},
year = {{2026}},
}