Savarese Marika, Netti Paolo A, Rega Nadia, Adamo Carlo, Ciofini Ilaria
Dipartimento di Chimica 'Paolo Corradini', Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, 80126 Napoli, Italy.
Phys Chem Chem Phys. 2014 May 14;16(18):8661-6. doi: 10.1039/c4cp00068d.
The mechanism of base to base intermolecular proton shuttling occurring in the excited state proton transfer reaction between 7-hydroxy-4-(trifluoromethyl)coumarin (CouOH) and concentrated 1-methylimidazole base (1-MeId) in toluene solution is disclosed here by means of a computational approach based on Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT). These methods allow us to characterize both the ground and excited state potential energy surfaces along the proton shuttling coordinate, and to assess the nature of the emitting species in the presence of an excess of 1-MeId. As a result, the tautomerism of CouOH is found to be photo-activated and, from a mechanistic point of view, the calculations clearly show that the overall driving force of the entire shuttling is the coumarin photoacidity, which is responsible for both the first proton transfer event and the strengthening of the following chain mechanism of base to base proton hopping.
本文通过基于密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）的计算方法，揭示了在甲苯溶液中7-羟基-4-（三氟甲基）香豆素（CouOH）与浓1-甲基咪唑碱（1-MeId）之间的激发态质子转移反应中发生的碱基间分子内质子穿梭机制。这些方法使我们能够沿着质子穿梭坐标表征基态和激发态势能面，并评估在过量1-MeId存在下发射物种的性质。结果发现，CouOH的互变异构是光激活的，从机理角度来看，计算结果清楚地表明，整个穿梭过程的总体驱动力是香豆素的光酸度，它既导致了第一次质子转移事件，又增强了随后的碱基间质子跳跃链式机制。
