Carboxylate Structural Effects on the Properties and Proton-Coupled Electron Transfer Reactivity of [CuO₂CR]²⁺ Cores

Abstract

A series of complexes {[NBu4]­[LCuII(O2CR)] (R = −C6F5, −C6H4(NO2), −C6H5, −C6H4(OMe), −CH3, and −C6H2( i Pr)3)} were characterized (with the complex R = −C6H4(m-Cl) having been published elsewhere (J. Am. Chem. Soc.201914117236)). All feature N,N′,N″-coordination of the supporting L2– ligand, except for the complex with R = −C6H2( i Pr)3, which exhibits N,N′,O-coordination. For the N,N′,N″-bound complexes, redox properties, UV–vis ligand-to-metal charge transfer (LMCT) features, and rates of hydrogen atom abstraction from 2,4,6,-tri-t-butylphenol using the oxidized, formally Cu­(III) compounds LCuIII(O2CR) correlated well with the electron donating nature of R as measured both experimentally and computationally. Specifically, the greater the electron donation, the lower is the energy for LMCT and the slower is the reaction rate. The results are interpreted to support an oxidatively asynchronous proton-coupled electron transfer mechanism that is sensitive to the oxidative power of the [CuIII(O2CR)]2+ core.

C(sp3)-H Fluorination with a Copper(II)/(III) Redox Couple

“…Our demonstration of C(sp 3 )-H fluorination with LCuF adds to the growing list of formally copper(III) intermediates in biological 45,46 and abiological 26,47 copper-mediated carbon-heteroatom bond-forming reactions. Alongside kinetic data reported by Tolman, 28,48 we established a correlation between the ligand basicity and the rate of HAA ( Fig. 4b).…”

C(sp3)-H Fluorination with a Copper(II)/(III) Redox Couple

“…Our demonstration of C(sp 3 )-H fluorination with LCuF adds to the growing list of formally copper(III) intermediates in biological 45,46 and abiological 26,47 copper-mediated carbon-heteroatom bond-forming reactions. Alongside kinetic data reported by Tolman, 28,48 we established a correlation between the ligand basicity and the rate of HAA (Fig. 4b).…”

From Synthetic to Biological Fe4S4 Complexes: Redox Properties Correlated to Function of Radical S‐Adenosylmethionine Enzymes

“…As demonstrated in Refs. [37][38][39][40][41][42][43][44], H-atom-abstraction (HAA) reactivity and selectivity are strongly influenced by the interplay of redox and acidobasic components of the HAA thermodynamic force, which are usually inter-dependent so that a lower E°is compensated to some extent by a higher pK a and vice versa. Thus, to probe the 5'-dAdo * properties relevant for enzymatic HAA reactivity, we first analyze electrochemical behavior of 5'-dAdo * in aqueous solution and then we compare it with its behavior in models of the [Fe 4…”