Theoretical Investigation for Two-state Reactivity of CO_2 Hydrogenation Catalyzed by Ru in Gas Phase

Gas-phase CO_2 catalyzed activation hydrogenation by Ru atoms was studied with density functional theory. Based on the structure optimization of different potential energy surfaces,there are two crossing points between singlet and triplet potential energy surfaces and there is a crossing point between quintet and triplet potential energy surfaces in the whole catalytic cycle. Spin transition probabilities in the vicinity of the intersections have been calculated by the Landau-Zener model theory. There are three minimum energy crossing points（MECPs） with strong spin-orbital coupling effect and higher spin transition probability,and all spin inversion occurred in s orbital and different d orbitals of ruthenium,indicating this is a typical two-state reactivity（TSR） reaction. Finally,the lowest energy reaction path is ensured.

QM/MM study on the O_(2)activation reaction of 4-hydroxylphenyl pyruvate dioxygenase reveals a common mechanism forα-ketoglutarate dependent dioxygenase

The dioxygen activation catalyzed by 4-hydorxylphenyl pyruvate dioxygenase(HPPD)were reinvestigated by using hybrid quantum mechanics/molecular mechanics(QM/MM)approaches at the B3LYP/6-311++G(d,p):AMBER level.These studies showed that this reaction consisted of two steps including the dioxygen addition/decarboxylation and hetero O-O bond cleavage,where the first step was found to be rate-determining.The former step initially runs on a septet potential energy surface(PES),then switches to a quintet PES after crossing a septet/quintet minimum energy crossing point(MECP)5-7M2,whereas the rest step runs on the quintet PES.The reliability of our theoretical predictions is supported by the excellent agreement of the calculated free-energy barrier value of 16.9 kcal/mol with available experimental value of 16-17 kcal/mol.The present study challenges the widely accepted view which holds that the O2activation catalyzed byα-keto glutamate(α-KG)dioxygenase mainly runs on the quintet PES and provides new insight into the catalytic mechanism ofα-KG dioxygenase and/or other related Fe(Ⅱ)-dependent oxygenase.

Molecular mechanism of aggregation-induced emission

Deep understanding of the inherent luminescence mechanism is essential for the development of aggregation-induced emission(AIE)materials and applications.We first note that the intermolecular excitonic coupling is much weaker in strength than the intramolecular electron-vibration coupling for a majority of newly termed AIEgens,which leads to the emission peak position insensitive to excitonic coupling,hence the conventional excitonic model for J-aggregation cannot effectively explain their AIE phenomena.Then,using multiscale computational approach coupled with our self-developed thermal vibration correlation function rate formalism and transition-state theory,we quantitatively investigate the aggregation effect on both the radiative and the nonradiative decays of molecular excited states.For radiative decay processes,we propose that the lowest excited state could convert from a transition dipole-forbidden“dark”state to a dipole-allowed“bright”state upon aggregation.For the radiationless processes,we demonstrate the blockage of nonradiative decay via vibration relaxation(BNR-VR)in harmonic region or the removal of nonradiative decay via isomerization(RNR-ISO)or minimum energy crossing point(RNR-MECP)beyond harmonic region in a variety of AIE aggregates.Our theoretical work not only justifies a plethora of experimental results but also makes reliable predictions on molecular design and mechanism that can be experimentally verified.Looking forward,we believe this review will benefit the deep understanding about the universality of AIE phenomenon and further extending the scope of AIE systems with novel applications.