Theoretical Study On The Correlation Between The Aromanticity And The Ring Stretching Vibration Roman Spectroscopy Frequency For Metal Ring

Aromaticity can be used to explain the structural characteristics of aromatic systems,bonding characteristics and stability,but also can be used to predict the direction of reaction and material synthesis.At present,the measurement of the aromaticity can only be realized by theoretical calculation method.So far,no feasible experimental method has been found,and it is of great research value to explore the feasible method for the determination of aromatic size.In this study,the symmetry analysis of the high-symmetric molecules is carried out by using the theory of group theory.It was found that the aromatic molecules have measurable ring-stretching A1'/A1 g vibrations with Raman activity The study of the ring stretching vibration of aromatic molecules using the Lagrangian motion equation showed that the transformation of the coordinates of the ring stretching vibration is related to its force constant.The ? and ? circulation which increase the interaction between atoms with aromatic,increase atomic force constant and the stability of aromatic substances.The RSVRSF(A1'/A1g)of the highly symmetric cyclic compound can be measured at the experimental level.It is not only a representation of the size for molecular force constant,but also related to the aromatic.Thus,the RSVRSF of molecule must be related to aromaticity.First,the geometrical optimization and RSVRSF calculation of planar metal [AlnHn]2-(n=3-6)?[BnHn]2-(n=3-6)system were carried out based on the B3LYP/6-311+G* and HF/6-311+G* methods in the Gaussian09 program.At the same time,the GIAO method was used to calculate its NucleusIndependent Chemistry Shieft(NICS),the imaginary debris reaction was designed to calculate the aromatic stabilization energy(ASE),and the correlation among NICS,RSVRSF and ASE was explored.The results showed that the RSVRSF calculated by the two methods showed a significant correlation with the corresponding NICS(min)/NICS(1.0).The target system RSVRSF and the corresponding ASE showed significant the first,the second correlation,respectively.The NICS(min)/NICS(1.0)of the target system showed significant quadratic correlation with the corresponding ASE.The RSVRSF,NICS(0.0)/ NICS(1.0)/NICS(min),ASE of [AlnXn]2-(X= F,Cl,Br,n= 3-5)system were calculated by B3LYP/6-311+G* method and discussed the correlation between them were discussed.The results showed that the RSVRSF of [Al3X3]2-(X=F,Cl,Br)had the significant correlation with the corresponding NICS(min/0.0)/NICS(1.0)values.Compared with [Al3X3]2-(X=F,Cl,Br),[Al4X4]2-(X=F,Cl,Br)and [Al5X5]2-(X=F,Cl,Br)were insignificantly correlated between the RSVRSF and NICS(min/0.0)/NICS(1.0).The correlation between the RSVRSF and ASE values of the [Al4X4]2-(X=F,Cl,Br)system is a significant correlation.The three-membered ring and five-membered ring correlation is prominent,the four-ring correlation is not obvious between the ASE values of the target system and NICS(min/0.0)/NICS(1.0).The correlation between the aromaticity of Xn(X=B,Al,Ga,n= 3-6)system and RSVRSF was also studied by B3LYP/6-311+G* method.It was found that the RSVRSF and NICS(min/0.0)/NICS(1.0)of target system had significant secondary correlations.From the theoretical study on the correlation between RSVRSF and the aromatic of target system,RSVRSF can be used as a tool to measure the aromatic size of the substance in the experiment.