对苯二甲酸-双(4-甲氧基苯酯)及其衍生物的结构与光谱

在密度泛函理论B3LYP/6-31 G*水平上计算研究了对苯二甲酸-双(4-甲氧基苯酯)及其OH和F腰接取代化合物的几何结构与红外振动光谱和电子光谱性质。研究发现这类化合物的酯基碳氧原子与苯环形成不同的离域大π键,空间位阻效应和共轭效应使三个苯环位于不同平面上,二面角在53°～59°范围。含时密度泛函理论计算第一激发态的电子垂直跃迁能,表明最大吸收光谱全部源于分子中HOMO→LUMO的π→π*跃迁,对应的最大吸收波长数值位于370～384nm之间,属于紫外区。腰接基对这类化合物的几何结构影响不大,仅由于空间位阻效应,使苯环(1)和苯环(2)之间的二面角增大3°～4°,但对其所在苯环的变形及其氢的振动有一定影响。同时,腰接羟基使HOMO→LUMO的能隙略有减小,最大吸收波长略有增大。腰接氟时因弱的共轭效应使得HOMO→LUMO的能隙减小0.1209eV,导致最大吸收波长红移14nm。

Study on Structure and Spectra of 1,4-bis [(p-Methoxyphenoxy) Carbonyl]

Theoretical studies on 1,4-bis [(p-methoxyphenoxy) carbonyl] and ramification were carried out using the density functional theory at B3LYP/6-31+G* level to obtain optimized equilibrium structure, vibrational spectra and electronic spectra. The calculation results indicate that the carbon and oxygen (in the ester group) come into being different large pi 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 the pi --> pi* electron transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. And lambda(max) was obtained in 370-384 nm, belonging to the UV absorption area. The computed results show that the lateral substitutent 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 3 degrees-4 degrees. The introduction of the lateral substitutents has effects on vibrational spectra. The results showed that with the introduction of hydroxy the difference between E(HOMO) and E(LUMO) of the compound becomes small. While lambda(max) becomes large. Meanwhile, the difference between E(HOMO) and E(LUMO) reduces by 0.120 9 eV with the introduction of fluorin. This causes the biggest absorption wavelength to red shift 14 nm.