A series of polypyridine ruthenium （II） acetylide complexes, [（tpy）（bpy）RuC≡CC6H4R]^＋ （tpy = 2,2＇：6＇,2＂-terpyridine, bpy = 2,2＇-bipyridine; R = F （1）, C1 （2）, H （3）, Me （4） and OMe （5）） are investigated theoretically to explore their electronic structures and spectroscopic properties. Their ground/excited state geometries, electronic structures and spectroscopic properties are first calculated using density functional theory （DFT） and time-dependent DFT （TDDFT）. The absorption and emission spectra of the complexes in acetonitrile solution are also obtained by using TDDFT （B3LYP） method associated with the CPCM model. The calculations show that the energy levels of HOMOs for 1-5 are sensitive to the substituent on phenylacetylide ligand and increase with the same order of the electron-donating ability of the substituents; however, those of polypyridine-based LUMOs vary slightly. The lowest-energy absorptions and emissions for 1-5 are progressively red-shifted in the order of 1 ~ 2 〈 3 〈 4 〈 5 when the electron-donating groups are introduced into the phenylacetylide [igand. The phosphorescence of 1 are attributed to {[dxz（Ru） ＋π（C≡C）]→[π^＊（tpy）]} （3MLCT/3LLCT） transition, whereas those of 2-5 are originated from { [dxz/dxy（Ru）＋ π（C ≡C）＋g（C6H4R）] → [＊（tpy/bpy）] } （3MLCT/3LLCT） transitions.
The transport mechanisms of four-conjugated systems were comparatively studied by combining ATK and Gaussian 03 calculations.It was found that the charge-doped oligosilane behaved in a different way from the boron doped and phosphorus doped oligosilanes in terms of the transmission property.The charge-doped oligosilane showed almost no conductivity owing to the damage of the electron transfer path by charge-doping.By contrast,the boron doped and phosphorus doped oligosilanes were demonstrated to be good semiconductors and NDR behavior was observed for them.This is a reasonable result after the analysis of the transmission spectra,MPSH states,energy gap,conjugation effect,and scattering effect.
ZHANG GuiLing 1,YUAN HongLiang 1,ZHANG Hui 1,SHANG Yan 1,SUN Miao 1,LIU Bo 1 & LI ZeSheng 2 1 College of Chemical and Environmental Engineering,Harbin University of Science and Technology,Harbin 150080,China 2 State Key Laboratory of Theoretical and Computational Chemistry
The charge-doping effect on the geometric and the electronic structures of organosilicon oligomers nSix(C=C)+y has been studied using density functional theory. Charge-doping can significantly lower the excitation energies. Interchain hole hopping mainly occurs between the π-conjugated units. A doped nSix(C=C)+y oligomer can undergo a structural rearrangement. The simulated UV/vis absorption peak of the rearranged structure is located at higher energy than the non-rearranged one. The hole transfer rate is significantly decreased if a doped molecule undergoes a rearrangement. These results offer a basis to explain previously observed experimental phenomena.
YANG LuQing SHANG Yan ZHANG Hui SUN Miao LIU Bo ZHANG GuiLing
