Quantification of the Electrostatic Effect on Redox Potential by Positive Charges in a Catalyst Microenvironment

Abstract

Charged functional groups in the secondary coordination sphere (SCS) of a heterogeneous nanoparticle or homogeneous electrocatalyst are of growing interest due to enhancements in reactivity that derive from specific interactions that stabilize substrate binding or charged intermediates. At the same time, accurate benchmarking of electrocatalyst systems most often depends on the development of linear free-energy scaling relationships. However, the thermodynamic axis in those kinetic–thermodynamic correlations is most often obtained by a direct electrochemical measurement of the catalyst redox potential and might be influenced by electrostatic effects of a charged SCS. In this report, we systematically probe positive charges in a SCS and their electrostatic contributions to the electrocatalyst redox potential. A series of 11 iron carbonyl clusters modified with charged and uncharged ligands was probed, and a linear correlation between the νCO absorption band energy and electrochemical redox potentials is observed except where the SCS is positively charged.

A guide to secondary coordination sphere editing

“…123,124 In a recent contribution, Berben and co-workers studied electrostatic effects arising from the incorporation of positive charge onto an [Fe 4 N(CO) 12 ] À cluster through the incorporation of methyl-1,3,5-triaza-7-phosphaadamantane ( Me PTA + ) (Scheme 44). 125 Further, they observed that incorporation of four positively charged groups in the SCS manifested in a change of ca. 600 mV in reduction potential.…”

Atomically Precise Ni–Pd Alloy Carbonyl Nanoclusters: Synthesis, Total Structure, Electrochemistry, Spectroelectrochemistry, and Electrochemical Impedance Spectroscopy

“…6 , 7 The molecular nature of these clusters allows us to gain detailed structural insight into the electrocatalytic active species and into the overall mechanism occurring in the catalyst microenvironment. 8 In this sense, the study of larger and larger molecular clusters such as HNMCCs represents an exciting frontier that could create a bridge to contemporary nanomaterials for electronic and electrochemical applications. 9 − 13 …”

“…6,7 The molecular nature of these clusters allows us to gain detailed structural insight into the electrocatalytic active species and into the overall mechanism occurring in the catalyst microenvironment. 8 In this sense, the study of larger and larger molecular clusters such as HNMCCs represents an exciting frontier that could create a bridge to contemporary nanomaterials for electronic and electrochemical applications. 9−13 The redox behavior of HNMCCs has been investigated by electrochemical and spectroelectrochemical methods, and recently, we reported the first two cases of multivalence in large Ni−Pd molecular nanoclusters.…”

“…This electron-sink behavior enables the application of metal carbonyl clusters in electrocatalytic processes . In particular, molecular Fe and Co carbonyl clusters have been employed as electrocatalysts for the two-electron reduction of two protons to molecular hydrogen and for the two-electron reduction of H + and CO 2 to formate. , The molecular nature of these clusters allows us to gain detailed structural insight into the electrocatalytic active species and into the overall mechanism occurring in the catalyst microenvironment . In this sense, the study of larger and larger molecular clusters such as HNMCCs represents an exciting frontier that could create a bridge to contemporary nanomaterials for electronic and electrochemical applications. − …”

A Mesoionic Carbene–Pyridine Bidentate Ligand That Improves Stability in Electrocatalytic CO2 Reduction by a Molecular Manganese Catalyst

“…The scaling relationship between E pc,1 versus ν CO bands in isostructural Mn(bpy) systems measured in an ACN solution from literature reports and the data presented here was used to probe the combined inductive and electrostatic effects imparted by MIC ligands. 50 Interestingly, C MIC-py exhibited the same trend as R-bpy (R = [4,4′]-H, -OH, -tertbutyl, and -methyl) and C triazol-py, whereas N MIC-py is offtrend by ∼180 mV (Figure 6 and Scheme S1). 6,23,43,51 The substitution of alkyls for aryls along the MIC fragment is also known to play a significant role in the π-accepting ability; however, to the best of our knowledge, no standard procedure or model has been introduced to analyze the electronic properties of these ligand types.…”