Study On Structures And Properties Of The Triphenylene, 1,4-bis [(p-methoxyphenoxy) Carbonyl] And Their Derivatives

Discotic liquid crystals of triphenylene and its derivatives have good charge-transport nature. Molecule and molecular ion structures optimization and frequency calculation of triphenylene, hexaazatriphenylene, and their derivatives have been carried out at of B3LYP/6-31G** level, and their most stable configurations were obtained. On the basis of the most stable geometries, the relationships of the energy with rotation degrees and intermolecular distances between the dimer have been calculated, and the lowest energy points were obtained. Based on the semi-classical model of the charge transport, the charge transport rate constants have been studied. Introduction of F, SH, OH and OR groups made the positive charge transport rate constants reduced clearly, but had little effect on negative charge transport. The results predict that HATH has the smallest positive charge transport rate and the largest negative charge transport rate. Introduction of SH, OH, OR and F groups make the positive charge transport rate increased, and negative charge transport rate reduced. The length of alkoxy group has little effect on charge transport.Diphenyl terephthalate is a good liquid crystal unit, the liquid crystal properties are affected by middle-linkages, lateral substituent and 4-substituting terminal groups. Theoretical studies on 1,4-bis [(p-methoxyphenoxy) carbonyl] and derivatives have been carried out at B3LYP/6-31+G* level to obtain optimized equilibrium structures, vibrational spectra and electronic spectra. The calculation results indicate that the carbon and oxygen (in the ester group) come into being different largeπ-bonds with the benzene circles because of place blocking and conjugate effect. On this basis, the first excited state electronic transition energy was calculated by time-dependent density function theory. The calculated results show that the largest absorption spectra of the title compounds were obtained from theπ→π* electron transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. Andλmax is obtained in 370~384 nm, belonging to the UV absorption area. The computed results show that the lateral substituent of 1, 4-bis [(p-methoxyphenoxy) carbonyl] has little effects on molecular structure. Because of place blocking, the dihedral angle between benzene (1) and benzene (2) augments 3o～4o. The introduction of the lateral substituent has effects on vibrational spectra. The results showed that with the introduction of hydroxy difference between EHOMO and ELUMO of compound becomes low. Andλmax becomes large. At the same time, the difference between EHOMO and ELUMO reduces 0.1209 eV with the introduction of fluorin. This causes the biggest absorption wave length red shift 14 nm.