Oriented Internal Electrostatic Fields Cooperatively Promote Ground- and Excited-State Reactivity: A Case Study in Photochemical CO₂ Capture

Abstract

Oriented electrostatic fields can exert catalytic effects upon both the kinetics and thermodynamics of chemical reactions; however, the vast majority of studies thus far have focused upon ground state chemistry and rarely consider any more than a single class of reaction. In the present study, we first use density functional theory (DFT) calculations to clarify the mechanism of CO2 storage via photochemical carboxylation of o-alkylphenyl ketones, originally proposed by Murakami et al. (J. Am. Chem. Soc. 2015, 137, 14063); we then demonstrate that oriented internal electrostatic fields arising from remote charged functional groups (CFGs) can selectively and cooperatively promote both ground-and excited-state chemical reactivity at all points along the revised mechanism, in a manner otherwise difficult to access via classical substituent effects. What is particularly striking is that electrostatic field effects upon key photochemical transitions are predictably enhanced in increasingly polar solvent, thus overcoming a central limitation of the electrostatic catalysis paradigm. We explain these observations, which should be readily extendable to the ground state.

Using internal electrostatic fields to manipulate the valence manifolds of copper complexes

“…This work has included (i) the use of bulk, homogeneous electric fields, 6–8 (ii) the study of anion effects on reaction selectivity, 9 (iii) the study of electrostatic stabilization of in situ -generated radical species, 10–14 and (iv) in-depth computational studies on reaction barrier (de)stabilization of organic molecules bearing charged functional groups. 15–20 Limited examples are known of transition metal complexes that use oriented internal electrostatic fields to tune the properties of the system. The Tolman group reported cupric hydroxide compounds bound by NNN pincer-type bis(carboxamide)pyridine ligands, wherein charged residues were incorporated at the para positions of the carboxamide aryl rings.…”

Ordered Solvents and Ionic Liquids Can Be Harnessed for Electrostatic Catalysis

“…12 While these experiments are difficult to scale for chemical synthesis, we have shown that the electric fields from remote charged functional groups, embedded on the substrate or a catalyst, can be used to catalyse chemical reactions and alter their outcome. [13][14][15][16][17][18][19][20][21][22][23][24][25] The charged group can be a Lewis acid, or an acid or base, whose charge and hence electric field, can be altered with pH. While again much of the work to date has been computational, experiments have validated these predictions in a growing number of systems.…”

“…Or indeed, solvents could be pre-ordered in other ways such as using microfluidics. 24 The structures are rendered using CYLview program. 52 In this work, we use both Drude oscillator based polarizable classical molecular dynamic (MD) simulations and multiscale quantum chemical calculations to determine if an ordered solvent environment is enough to catalyse a chemical reaction in the absence of an applied electric field.…”

“…The optimized structures of reactant (b) and transition state (c) of this reaction and the direction of the EEF. For more details of the reaction, see Ref 24. The structures are rendered using CYLview program 52.…”

Electrostatically Tuning the Photodissociation of the Irgacure 2959 Photoinitiator in the Gas Phase by Cation Binding

“…Predicting the impact of chemical modification, or application of OEFs, on photoactivity is not straightforward as different excited states have different polarities and polarizabilities and thus respond differently. 9,10,15 This in turn has complex follow-on effects on intersystem crossing rates, triplet lifetimes and other factors affecting photodissociation.…”