半三明治配合物的芳香性及其与环伸缩振动拉曼光谱频率的相关性

Correlation Between the Ring Stretching Vibration Raman Spectroscopic Frequency and Aromaticity for Half Sandwich Complexes

寻找实验上定量测定芳香性分子芳香性大小的方法是科学家一直追求的一个目标,应用拉曼光谱测量半三明治配合物芳香性大小是一项新的尝试。采用Gaussian09计算程序中的密度泛函理论(DFT),对(η6-C6X6)和半三明治配合物[(η6-C6X6)M]n+(X=F～Br,M=Ti～Mn,n=1,2)进行几何优化,并对其几何结构、静电引力、稳定化能ΔE、核独立化学位移(NICS)值及环伸缩振动拉曼光谱频率(RSVRSF)大小进行了理论计算。结果表明:取代苯及其形成的半三明治配合物的NICS值均为负值,均为芳香性分子;取代苯及其半三明治配合物中均存在A1g或A1对称性的RSVRSF,且其峰强度均很大,其NICS绝对值、RSVRSF值均随着F,Cl,Br取代的顺序逐渐减小,均呈高度正相关,且相关性系数均达到0.99以上,理论预测可通过实验测定其RSVRSF值测定该类物质的芳香性大小。

It is a pursuing goal to find an experimental method for determining the aromatic size of aromatic molecules for scientists.It is a new attempt to measure the aromaticity degree of half-sandwich complexes using Raman spectroscopy.The calculations for the geometries optimization,electrostatic forces,stabilization energies,nucleus independent chemical shifts(NICS)and values of the Raman spectroscopy for(η^6-C6X6)and half sandwich complexes[(η^6-C6X6)M]^n+(X=F^Br,M=Ti^Mn,n=1,2)were conducted using density functional theory(DFT)method within Gaussian09 process package.The results showed that,for all the(η^6-C6X6)and half sandwich complexes,the values of NICS were all negative.These kinds of molecules all were aromatic.There were strong Ring Stretching Vibration Raman Spectroscopic Frequency(RSVRSF)peaks with A1g/A1 symmetric in the(η^6-C6X6)and its half sandwich complexes.The RSVRSF values and the absolute NICS values of the(η^6-C6X6)and its half sandwich complexes gradually decreased with the order of F,Cl,and Br,showing a highly positive correlation,and the correlation coefficients were above 0.99.It is theoretically predicted that the determination of the aromatic degree is possible by the experiment determination of the RSVRSF values for the(η^6-C6X6)and its half sandwich complexes.