C_(2n)H_3和C_(2n)H_3^+(n=4,5,6,7)的结构、稳定性和光谱  

Structure,Stability and Spectra of C_(2n)H_3 & C_(2n)H_3^+(n=4,5,6,7)

作　　者：任洁[1] 武海顺[1] 

机构地区：[1]山西师范大学化学与材料科学学院,山西临汾041004

出　　处：《山西师范大学学报（自然科学版）》2006年第3期38-44,共7页Journal of Shanxi Normal University(Natural Science Edition)

基　　金：山西省青年科学基金资助项目(20051011);国家自然科学基金资助项目(20471034)

摘　　要：本文采用密度泛函理论(DFT-B3LYP),在6-31G*的水平上对C2nH3和C2nH+3(n=4,5,6,7)所有可能的几何构型进行了优化和振动频率的计算,进一步得到了C2nH3(n=4,5,6,7)最稳定构型的垂直和绝热电离能,并在这个水平上用含时的密度泛函理论(TD-B3LYP)计算它们的垂直激发能.结果表明中性分子和相对应的阳离子的基态构型几乎是一样的,具有聚炔烃线性链结构的C8H3和C12H3自由基及其他们的阳离子都具有30~60 cm-1的低频振动模式.通过激发能和电离能的研究发现C2nH3自由基(n=4,5,6,7)基态平衡几何结构的电离能较大,中性分子不易发生电子跃迁,而且不易失去一个电子变为阳离子,所以C2nH3自由基(n=4,5,6,7)基态平衡几何结构比相对应的阳离子要稳定.Density functional theory （DFT） has been used to investigate the geometries, vebrational frequencies of C2nH3 and C2nH3 （n =4, 5, 6, 7）. Vertical electronic transition energies of C2nH3 and C2nH3 （n = 4, 5, 6, 7） are calculated by the time-dependent density functional theory （TD-DFT）. In addition, the adiabatic ionization potential and vertical ionization potential of C2nH3（n =4, 5, 6, 7） are obtained. The results show that the ground state structures of C2nH3 and C2nH3^＋ （n = 4, 5, 6, 7） are same. The structure is open chain with C2v symmetry showing polyacetylenic structure, the number of carbon atom of which is 8 and 10. The structure is single ring with Cs symmetry, the number of carbon atom of which is 12 and 14. The stability of C2nH3 and C2nH3 （n = 4, 5, 6, 7） increase as the number of carbon atoms increase, respectively. The lowest frequency origins in the 30cm^- 1～60cm^-1 of C2a H3 and C2nH3 （ n = 4,5,6,7 ） which show polyacetylenic structure. Theoretical investigations of vertical transition energies and ionization potentials found that C2nH3 （n =4,5,6,7 ） has the large ionization potential （IP）. It is opposite of the report for C2n＋1H3. And the electron of C2nH3 （n= 4, 5, 6, 7 ） is difficult to transfer and lose an electron. So the ground state isomer of C2nH3 （n = 4,5,6,7 ） radical is stable than that of C2nH3 （n =4,5,6,7） cation.

关 键 词：C2nH3 C2nH3^+ 激发能 电离能 

分 类 号：O641.12[理学—物理化学]