给、吸电子基团对芳香共轭体系电子结构影响的密度泛函理论研究

DFT study on electronic structures of aromatic conjugation system connected with electron donating and witharawing group

采用密度泛函理论,在B3LYP/6-31G*方法水平上对8个连接有给、吸电子基团的芳香共轭体系的稳定性、偶极矩、静电荷分布和前线轨道能级进行了研究,并采用TD/DFT方法进一步研究了它们的电子光谱.结果表明a-1,b-1,c-1和d-2分子比它们的同分异构体要稳定;对于苯、呋喃、吡咯与乙烯形成的共轭体系,吸电子基团连接在乙烯一端,给电子基团连接在芳香环上使体系的偶极距增强,而吡啶则相反;前线轨道能级差较小的是吸电子基团连接在芳香环一端的体系,相应的分子最大吸收波长也较大.

Geometric structures of eight aromatic conjugation system, which were connected with electron donating and witharawing group, were optimized at B3LYP/6-31G^＊ level. Their frontier molecular orbital energy levels and electronic spectra were obtained with TD-DFT method.The results showed that a-1 ,b-1, c-1 and d-2 molecules are more stable than their isomers.For the Phenyl ethylene,2-vinylfuran and 2-vinylpyrrole, when nitryl connected with ethylene and amidogen connect with the aromatic ring,the dipole moments were increased. Reverse effect was found for pyridine derivatives. When electron witharow group was linked to aromatic ring, lower energy gap was resnhed correspondig to larger absorption wavelength.