Our density functional theory (DFT)/time-dependent DFT (TDDFT) calculations for the sensing mechanism of a series of sulfoxide based metal-responsive fluorescent chemosensors, suggested that the intramolecular charge transfer (ICT) is not a reasonable mechanism for these chemosensors. The calculated electronic transition energies, the corresponding oscillator strengths of these chemosensors and the involving frontier molecular orbital analysis indicated that there is no obviously ICT state with a transition oscillator strength approaching to zero. The fluorescence quenching of these chemosensors cannot be explained by ICT process. The ground state optimized structures of chemosensors and their complexes indicated that there might be twisted excited configuration for these chemosensors and the twisted excited state configuration may response for the fluorescence quenching. The configuration change can be blocked in the Zn complex that is responsible for these complexes showing fluorescence emission enhancement. In order to understand the function of the sulfoxides group in these metal-responsive fluorescent chemosensors, excited state configuration optimization as well as the excited state hydrogen bond effect on the fluorescence enhancement in the aqueous solvent will be conducted.

By using the time-dependent quantum wave packet method, we report a detailed dynamics study of H exchange reaction $H'(²S) + CH(X²\Pi) → H(²S) + CH'(X²\Pi)$ and the isotope effects of $H(²S) + CH(X²\Pi) → C(¹D) + H_2(X¹Σ^+_g)$ reaction on the 11A BHL potential energy surface. The reaction probabilities and integral cross sections have been obtained for the initial states $v = 0$ and $j = 1$ of the reactant molecules. The dense resonance structures in the reaction probabilities at all total angular momentums indicate complex-forming mechanisms for both $C + H_2$ and $H + CH$ products. A comparison between the results from centrifugal sudden approximation and those from close-coupled calculations demonstrates that the Coriolis coupling effects get more and more pronounced with increasing of $J$ for both $H$ exchange reaction and $CH$ decay reaction. The isotopic $D$ substitution of reactant significantly influences the $CH$ decay reaction. Moreover, it is revealed that the dynamical features such as partial wave contributions to the cross section are substantially different for these two channels.

Based on the time-dependent density functional theory (TDDFT), the excited state intramolecular proton transfer (ESIPT) mechanism of a new compound 1 chromophore synthesized and designed by Liu et al. [Journal of Photochemistry and Photobiology B: Biology., 138 (2014), 75-79] has been investigated theoretically. The calculations of primary bond lengths, angles and the IR vibrational spectra verified the intramolecular hydrogen bond was strengthened. The fact that reproduced the experimental absorbance and fluorescence emission spectra well theoretically demonstrates that the TDDFT theory we adopted is reasonable and effective. In addition, intramolecular charge transfer based on the frontier molecular orbitals demonstrated the indication of the ESIPT reaction. The constructed potential energy curves of ground state and the first excited state based on keeping the O-H distance fixed at a serious of values have been used to illustrate the ESIPT process. A little barrier of 2.45 kcal/mol in the first excited state potential energy curve provided the transfer mechanism. Further, the phenomenon of fluorescence quenching has been explained reasonably based on the ESIPT mechanism.

A quantum mechanical approach has been used to investigate the antioxidative mechanism for scavenging •OOH and •OH radicals using mangiferin in solution phase. Mangiferin is also used as a potent applicant for organic semiconductor. The charge-transport properties in mangiferin have been studied based on the first-principle DFT combined with the Marcus-Hush theory. Density functional theory (DFT) calculations at the B3LYP/6-311+G(d,p) level were used to optimize mangiferin and its different forms. The lowest theoretical bond dissociation enthalpy (BDE) value for 7-OH site of mangiferin in water, indicates that 7-OH group is important in the antioxidant activity. The relative values of enthalpies also show that oxidation of mangiferin by •OOH and •OH radical is an exothermic process. The predicted maximum electron mobility value of mangiferin is 0.148 cm² $V^{-1} s^{-1},$ which appears at the orientation angle near 49°/311° of conducting channel on the reference planes ab. Theoretical investigation of natural semiconductors is helpful for designing higher performance electronic materials used in biochemical and industrial field to replace expensive and rare organic materials.

Product Polarizations for the exchange reaction $H'+HS$ and its isotopic variants on an accurate $1A'$ potential energy surface have been studied at collision energies of 10 kcal/mol by using the quasi-classical trajectory method (QCT). Product rotational angular momentum distributions $P(θ_r)$ and $P(\phi_r)$ are calculated in the center-of-mass (CM) frame. Moreover, three generalized polarization-dependent differential cross sections (PDDCSs) are also computed. The results demonstrated that the isotopic effect displays sensitive effect on the product vector correlations. The reaction mechanism was discussed based on the properties of stereodynamics and the reactive trajectories.