卤素掺杂聚甲基苯基硅烷的电子结构的理论研究

Halogen Doping Effect on Electronic Structure of Poly(methylphenyl)silane:a Theoretical Study

采用密度泛函理论(DFT)研究卤素(F2,Cl2,Br2,I2,ICl)掺杂聚甲基苯基硅烷(PMPSi)的电子结构.在BH&HLYP/6-31G*水平上优化PMPSi,交错构象为最稳定构象.在此构象上优化卤素掺杂PMPSi并比较结构变化,进一步探讨复合物的前线轨道能量、吸收光谱等性质.结果表明,最高占据轨道(HOMO)的能量几乎保持不变,而最低空轨道(LUMO)的能量降低,能隙按Cl2>F2>ICl>Br2>I2顺序减小.以致电子由HOMO-1→LUMO跃迁,使复合物在吸收光谱中发生红移,在可见光区有较强的吸收峰.自然键轨道(NBO)理论分析表明电荷从主链向卤素转移.所有复合物经基组叠加误差(BSSE)校正后的相互作用能为-0.61～-3.20 kcal/mol,且掺杂剂的极性越大,复合物的相互作用能越大.并讨论掺杂剂位置对复合物的能隙和相互作用能的影响.该研究为PMPSi的相关研究提供理论线索和依据.

In order to well understand the halogen（F2,Cl2,Br2,I2,ICl） doping effect on electronic structure of poly（methylphenyl）silane（PMPSi）,a theoretical investigation on halogen doped models has been performed using density functional theory（DFT）.The optimized structures of PMPSi are obtained at the BH＆HLYP/6-31G＊ level,and the stagger conformation is the most stable conformation among three isomers.Halogen doped PMPSi were optimized at the BH＆HLYP level based on the stagger conformation,and the changes of geometry parameters are compared for PMPSi and halogen doped PMPSi.Furthermore,frontier molecular orbital energies and electronic absorption spectra of halogen doped PMPSi are investigated.The results show that energy of the highest occupied molecular orbital（HOMO） almost keeps the same when PMPSi is doped by halogen,but energy of the lowest unoccupied molecular orbital（LUMO） becomes lower,the energy gap is therefore decreased according to the order Cl2＆gt;F2＆gt;ICl＆gt;Br2＆gt;I2.When PMPSi is doped by halogen,electron transition is assigned to the HOMO-1→LUMO,it leads to red shift of the absorption spectrum of complex,and presents relative strong absorption peak in visible region.Natural bond orbital（NBO） analyses were performed to study the charge distribution of halogen doped PMPSi,it is found that charge transfer from backbone to halogen in the complex.The interaction energies of all the complexes which were corrected for basis set superposition error（BSSE） are from-0.61 to-3.20 kcal/mol.The result what arouse most interest is,the higher polarity of dopant,the larger interaction energy of complex.In addition,the influence of position of dopant on energy gaps and interaction energies of all complexes is discussed in our present work.This study is expected to provide theoretical clues and foundation for future research on improving the photoelectric property of PMPSi.