Abstract
The heterocyclic quinolin molecules and the precursor have been studied by using the Density Functional Theory (DFT). The geometry and energy of ground state and the vertical transition of excited states are calculated and optimized by the three methods, B3LYP, B3P86 and B3PW91, via the two basis set, 6-31G(d,p) and 6-31+G(d). According to the calculation results, the quinolin molecules are kept o-QDM-like structure within singlet electronic ground state and biradicl-liked structure within triplet ground state. Comparing with the laser flash-photolysis study to the sultines, to assign o-xylene has an S → Sn transition at 370 nm, 2,3-naphthoquinodimethane has an S → Sn transition at 420 nm and a T → Tn transition at 520 nm, and 2,3-quinoxalinodimethane has three T → Tn transition near 280 nm, 350 nm and 420 nm individually. Through the comparison by the experiments and the calculation for the precursor, benzosultine, we discovered that the quinolin molecules with different structure hold dissimilar reaction nature. By reaction mechanism kinetics calculation, the photodissociation process for the heterocyclic quinolin molecules has been figured: the photodissociation of the quinolin molecule without containing the nitrogen atoms, such as o-xylene, should move around the singlet potential surface and the nitrogen-contained quinolin molecule, like 2,3-quinoxalinodimethane, would process the dissociation pathway via the triplet potential surface by inter-system crossing (ISC).