Abstract

This work investigates the spectroscopic and electrochemical properties of Ru(ttpy)(4-BQ-tpy)2+, where ttpy is 4-methylphenyl-2,2 ':6 ',2 ''-terpyridine and 4-BQ-tpy is 4 '-(2,5-benzoquinonyl)-2,2 ':6 ',2 ''-terpyridine, in the context of electrochemical CO2 capture. Cyclic voltammetry in DMSO revealed two quinone-centered reduction processes for both the free ligand and the Ru complex, with all potentials referenced to the Fc/Fc+ couple. Upon exposure to CO2, the second reduction wave showed a pronounced anodic shift in both systems, consistent with adduct formation between the doubly reduced quinone species and CO2. The free ligand displayed a stronger response, with log K = 11.3, whereas the Ru complex showed a lower but still significant association constant of log K = 7.8, indicating that coordination to Ru attenuates but does not suppress quinone-based CO2 binding. Additional fitting analysis supports that the electrochemical behavior is better described by an n = 2 binding model under the present experimental conditions. Complementary DFT calculations identified stable mono- and bis-CO2 adducts for the doubly reduced complex, supporting the proposed reversible capture process. These results show that Ru-quinone hybrid systems remain competent electrochemical CO2 capture platforms while also introducing metal-based electronic functionality that may be relevant for integrated capture/activation schemes.