Evaluation of a Ruthenium(II) (2,2′:6′,2′′‐Terpyridine)–Benzoquinone Complex for Electrochemical CO ₂ Capture

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 CO 2 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 CO 2 , the second reduction wave showed a pronounced anodic shift in both systems, consistent with adduct formation between the doubly reduced quinone species and CO 2 . 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 CO 2 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‐CO 2 adducts for the doubly reduced complex, supporting the proposed reversible capture process. These results show that Ru–quinone hybrid systems remain competent electrochemical CO 2 capture platforms while also introducing metal‐based electronic functionality that may be relevant for integrated capture/activation schemes.