Combined static and dynamic quenching in micellar systems—closed-form integrated rate laws verified using a versatile probe

Abstract

We demonstrate that the 3-aminoperylene radical cation is a near-ideal probe for investigating kinetic and transport processes in SDS micellar systems. Its isolated generation by two-photon ionization at a wavelength where most quenchers are transparent (532 nm) is free from side reactions; no exit from the micelles is detectable on a millisecond timescale; and its unquenched lifetime is as long as 350 ms, thus allowing the study of quenching processes over a time frame spanning at least 7 orders of magnitude. The lipophilic antioxidant ascorbyl palmitate reconverts it to its parent compound through the interplay of static and fast dynamic intramicellar quenching as well as through subsequent slow intermicellar migration. Using this radical-cation probe, we have successfully validated closed-form expressions which we derived for the probe decay in all these situations. From these functions, we also obtained an exact and closed-form analytical result for Stern-Volmer experiments with combined static and dynamic intramicellar quenching.

Resveratrol Radical Repair by Vitamin C at the Micelle–Water Interface: Unexpected Reaction Rates Explained by Ion–Dipole Interactions

“…In this Figure, the H 2 Asc/micelle ratio changes by a factor of almost four, yet the initial post‐flash concentration of ResO remains completely unaffected. This eliminates an intramicellar (i.e., static) repair, which we recently found in the system aminoperylene radical cation/ palmitoyl ascorbate/ SDS . The experiments of the Figure further comprise a variation of the ResO concentration (through the laser intensity), such that in conjunction with the surfactant variation the ResO /micelle ratio is altered by a factor of up to nearly eight; nevertheless, this has no effect whatsoever on the rate constant of the strictly monoexponential decay, which is substantially faster than in homogeneous aqueous solution.…”

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser

“…, the most important raw materials for chemical syntheses, have originated in that way. It is based on storing, and possibly pooling, 8 – 15 photon energy in a catalyst molecule, utilizing that energy to activate a substrate through direct or relayed 16 electron transfer, and finally recovering the starting form of the catalyst by a complementary electron donor or acceptor, which might also be a sacrificial additive. In consequence, the four key characteristics of a photoredox catalytic system are its operating wavelength, the oxidative or reductive power its activating state possesses, the lifetime of that state, and the susceptibility to catalyst-destroying parasitic reactions.…”

“…By virtue of its standard potential of –2.9 V ( ref. 19 ) it qualifies as a super-reductant; yet, its natural lifetime of hundreds of microseconds, 20 although typically reduced to less than one microsecond under actual operating conditions, 12 – 15 , 21 compares very favourably with that of excited states of very high reductive power currently available for photoredox catalysis. 8 – 11 , 22 – 24 The fourth criterion primarily includes processes inherent to the catalytic system itself, mainly photochemical side reactions and intrinsic chemical irreversibility, which the present work addresses; beyond this, extrinsic processes such as a poisoning of the catalyst by the substrate or reaction products are conceivable, but need to be investigated on a case by case basis for each application.…”

Interações Competitivas De Complexos De Rutênio Contendo Dimetilsulfóxido E Ligantes N-Heterocíclicos Com Albumina De Soro Humano

“…RuCl(dmso)(dmbpy) 2 ]Cl (Figura 2B) indica que o mecanismo de supressão de fluorescência da albumina induzida pelo derivado metálico não é exclusivamente dinâmico ou estático, mas sim um mecanismo híbrido ou intermediário (dinâmico + estático),45 no qual deve-se considerar a esfera de ação do complexo metálico. Nesse caso, a equação de Stern-Volmer é modificada e a constante de supressão é dada pela combinação das constantes dos dois mecanismos, conforme…”