Carboxylate pentapyridines: Pathway to surface modification and tuneable catalytic proton reduction

Marissa K. Melvin, Paul K. Eggers, Colin L. Raston

Research output: Contribution to journalArticlepeer-review


The ability to synthetically tune catalytic performance is a key advantage in the use of molecular catalysts. A series of cobalt pentapyridine carboxylate esters [Co(Py5Me2COOMe)(CH3CN)]2+ (Co-Me), [Co(Py5Me2COOn-Pr)(CH3CN)]2+ (Co-Pr) and [Co(Py5Me2COOPh)(CH3CN)]2+ (Co-Ph) were successfully synthesised and characterised through HD-MS, FT-IR and cyclic voltammetry. Electrochemical studies reveal the complexes are active for electrocatalytic proton reduction in acetonitrile with acetic acid as the proton source. At an acid concentration of 2 mM, the required overpotential for proton reduction was calculated to be 465 mV for Co-Me, 485 mV for Co-Pr and 360 mV for Co-Ph. The rate constant is calculated to be 9.41 s−1, 4.09 s−1 and 7.25 s−1 for complexes Co-Me, Co-Pr and Co-Ph respectively. The cobalt carboxylate complex [Co(Py5Me2COO)(OH)]1+ (Co-COOH) was used to prepare chemically modified electrodes from fluorine doped tin oxide (FTO) coated glass and glassy carbon with a calculated surface coverage of 6.38 × 10−11 mol/cm2 and of 6.18 × 10−11 mol/cm2 respectively. The successful reduction of catalytic overpotential through esterification offers an alternative pathway for the design of molecular catalysts.

Original languageEnglish
Article number116177
Number of pages7
Early online date19 Oct 2022
Publication statusPublished - 1 Dec 2022


  • Carboxylate ester
  • Electrocatalyst
  • Polypyridyl
  • Proton reduction


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