A photobasic D–A fluorophore with a high intramolecular charge-transfer as a model strategy for designing organic proton-coupled electron-transfer modulators: an analysis based on steady-state fluorescence, isotopic effect and theoretical study

Abstract

The modulation of the photo-induced proton coupled electron-transfer (PCET) mechanisms is a topic of great interest by its pivotal role in energy-transfer processes, development of fuel cells and activation of...

Exploring binding chemistry of alkali/alkaline earth cations in solution through modulation of intramolecular charge-transfer in an excited ambidentate organic fluorophore

“…The almost unique preference of most of the first transition row cations as medium hard/borderline acids to promote a quenching response with minimal or unappreciable CT-enhancement or LE-enhancement/CT-decay response confirms their expected preference to interact with the borderline heterocyclic nitrogen-10 base. 44 This makes probe 3k in an extraordinary platform to analyze the variability in the binding chemistry of AM cations as hard acids by interaction with chemical functionalities of different hardness (methoxy, enolate and heterocyclic nitrogen-10), as chemistry well distinguishing the binding chemistry of first transition row cations.…”

“…Both features are contrary to the expected tendency based on the HSAB principle. 44 We think that this particular disagreement with the HSAB theory can be attributed to the large difference (higher than 1.0 Å) among the values of the ionic radius of the group I and II cations ( e.g. , from 0.6 Å for Li + to 1.67 Å for Cs + ), 56 which was not found for the rest of groups in the Periodic Table, with the elements showing slight changes (<0.2 Å) 56 in the magnitude of their ionic radius within the same group.…”