Zhuang Zhiping, Cheng Jianbo, Wang Xu, Zhao Bing, Han Xiaoxia, Luo Yulie
Key Laboratory for Supermolecular Structure and Materials of Ministry of Education, Jilin University, 10th Qianwei Road, 2699 Qianjin Street, Changchun 130012, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2007 Jun;67(2):509-16. doi: 10.1016/j.saa.2006.08.008. Epub 2006 Aug 12.
The molecular geometry and vibrational frequencies of 4,4'-bipyridine (BPE) in the ground state were calculated using density functional theory (DFT) methods (B3LYP) with 6-31++G(d,p) basis set. The optimized geometric bond lengths and bond angles are obtained by DFT employing the hybrid of Beckes non-local three parameter exchange and correlation functional and Lee-Yang-Parr correlation functional. Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and near-infrared surface-enhanced Raman scattering (NIR-SERS) spectra of BPE on the silver foil substrate have been recorded. All FT-IR, FT-Raman and NIR-SERS band were assigned on the basis of the B3LYP/6-31++G(d,p) method. The vibrational frequencies obtained by DFT(3LYP) are in good agreement with observed results. The NIR-SERS of BPE excited by 1064nm laser line is little difference with that excited by visible laser line. This phenomenon is result to the increase of the contribution of CHEM enhancement effect. Surface selection rules derived from the electromagnetic enhancement model were employed to infer the orientations of BPE on the silver foil substrate surface. Some vibrational frequency which are sensitive to the planar or non-planar structure of BPE, and to the dihedral angle were concluded.
采用密度泛函理论（DFT）方法（B3LYP），结合6-31++G(d,p)基组，计算了4,4'-联吡啶（BPE）基态的分子几何结构和振动频率。通过采用Beckes非局部三参数交换和相关泛函与Lee-Yang-Parr相关泛函的混合方法，利用DFT获得了优化的几何键长和键角。记录了BPE在银箔基底上的傅里叶变换红外（FT-IR）、傅里叶变换拉曼（FT-Raman）和近红外表面增强拉曼散射（NIR-SERS）光谱。所有FT-IR、FT-Raman和NIR-SERS谱带均基于B3LYP/6-31++G(d,p)方法进行归属。通过DFT（3LYP）获得的振动频率与观测结果吻合良好。1064nm激光线激发的BPE的NIR-SERS与可见激光线激发的结果差异不大。这种现象是由于化学增强效应贡献的增加所致。利用电磁增强模型推导的表面选择规则，推断了BPE在银箔基底表面的取向。得出了一些对BPE的平面或非平面结构以及二面角敏感的振动频率。
