Impact of chirality on the photoinduced charge transfer in linked systems containing naproxen enantiomers

[EN] The model reaction of photoinduced donor-acceptor interaction in linked systems (dyads) has been used to study the comparative reactivity of a well-known anti-inflammatory drug, (S)-naproxen (NPX) and its (R)-isomer. (R)- or (S)-NPX in these dyads is linked to (S)-N-methylpyrrolidine (Pyr) using a linear or cyclic amino acid bridge (AA or CyAA), to give (R)-/(S)-NPX-AA-(S)-Pyr flexible and (R)-/(S)-NPX-CyAA-(S)-Pyr rigid dyads. The donor-acceptor interaction is reminiscent of the binding (partial charge transfer, CT) and electron transfer (ET) processes involved in the extensively studied inhibition of the cyclooxygenase enzymes (COXs) by the NPX enantiomers. Besides that, both optical isomers undergo oxidative metabolism by enzymes from the P450 family, which also includes ET. The scheme proposed for the excitation quenching of the (R)- and (S)-NPX excited state in these dyads is based on the joint analysis of the chemically induced dynamic nuclear polarization (CIDNP) and fluorescence data. The H-1 CIDNP effects in this system appear in the back electron transfer in the biradical-zwitterion (BZ), which is formed via dyad photoirradiation. The rate constants of individual steps in the proposed scheme and the fluorescence quantum yields of the local excited (LE) states and exciplexes show stereoselectivity. It depends on the bridge's length, structure and solvent polarity. The CIDNP effects (experimental and calculated) also demonstrate stereodifferentiation. The exciplex quantum yields and the rates of formation are larger for the dyads containing (R)-NPX, which let us suggest a higher contribution from the CT processes with the (R)-optical isomer.The work was supported by the Russian Foundation for Fundamental Research (14-03-00192, 14-03-00692). All QS calculations were carried out on a cluster computer in the regional center for shared computer equipment at the Ufa Institute of Chemistry of RAS.Khramtsova, E.; Sosnovsky, D.; Ageeva, A.; Nuin Plá, NE.; Marín García, ML.; Purtov, P.; Borisevich, S.... (2016). Impact of chirality on the photoinduced charge transfer in linked systems containing naproxen enantiomers. Physical Chemistry Chemical Physics. 18(18):12733-12741. https://doi.org/10.1039/C5CP07305GS1273312741181

Numerical modeling of intramolecular transformations of orto-substituted aromatic nitrozoxides

Работа посвящена исследованию реакции гибели ароматических нитрозооксидов, которые обладают уникальными свойствами, благодаря наличию у них цис- и транс- изомерии. Константы скорости гибели изомеров нитрозооксидов являются эффективными, т.е. описывают сложную совокупность элементарных превращений – конформационных и необратимых. Для численного анализа процесса разработана программа вычисления кинетических параметров реакции. Ввиду большого количества параметров реакции, решение обратной кинетической задачи требовало больших временных затрат. В связи с этим применялись технологии параллельных вычислений, что позволило сократить время вычислений примерно в 10 раз. С помощью разработанных алгоритмов построена кинетическая модель реакции, включающая в себя оптимизированные энергии Гиббса, константы элементарных стадий реакций и эффективные константы расходования изомеров нитрозооксидов. Анализ доказал необходимость учета внутримолекулярных превращений ароматических нитрозоксидов в реакции их гибели.//The work is devoted to the investigation of the deacay reaction of aromatic nitrosooxides, which have unique properties due to the presence of cis and trans isomerism. The rate constants of nitrosooxides isomer decay are effective, i.e. incluse a complex set of elementary transformations – conformational and irreversible. For numerical analysis of the process, a software has been developed for calculating the kinetic parameters of the reaction. In view of the large number of reaction parameters, the solution of the inverse kinetic problem required a large amount of time. In connection with this, parallel computing technologies were used, which allowed to reduce the calculation time approximately in 10 times. With the help of the developed algorithms, a kinetic model of the reaction is constructed, which includes optimized Gibbs energies, constants of elementary reaction stages and effective constants of nitroso isomers consumption. The analysis proved the necessity of taking into account intramolecular transformations of aromatic nitroxides in the reaction of their consuption.Работа выполнена при финансовой поддержке гранта 15-07-01764 "Оптимальное управление химическими реакциями металлокомплексного катализа"