2-氟-5-溴吡啶分子振动光谱的密度泛函理论研究

Density Functional Theory Studies on Vibrational Spectra of 2-Fluoro-5-bromopyridine

用密度泛函理论方法B3LYP以及 6 311++G(2df,2pd)基组对 2 氟 5 溴吡啶分子的平衡几何构型进行了优化并计算了该分子的振动谐力场 .使用Pulay的标度方法对理论力场进行了标度 .采用Wilson的GF矩阵方法 ,根据标度后的理论力场进行了简正坐标分析 ,对 2 氟 5 溴吡啶分子的振动基频进行了理论研究 ,得到了势能分布和红外振动频率 .与红外频率的实验值相比较 ,理论频率的均方差为 2 4cm-1.此外 ,根据振动模式的势能分布对此分子的振动基频进行了理论归属 ,并对前人的指认进行了修正和补充 .

The optimized geometries, vibrational force fields and infrared intensities of 2-fluoro-5-bromopyridine molecule were calculated by using density functional theory B3LYP method with 6-311 + + G (2df,2pd) basis set. The theoretical force field was scaled using the scaled quantum mechanical force field. The root-mean-squares deviation was found to be 24 cm(-1) for calculated frequencies. The assignment of the vibrational fundamentals for 2-fluoro-5-bromopyridine molecule was also performed according to the potential energy distributions.