Covington Cody L, Polavarapu Prasad L
Department of Chemistry, Vanderbilt University, 7330 Stevenson Center, Station B 351822, Nashville, TN 37235, USA.
Phys Chem Chem Phys. 2016 May 18;18(20):13912-7. doi: 10.1039/c6cp01247g.
A study utilizing the newly developed electronic dissymmetry factor (EDF) spectral analysis reveals that for [1,1'-binaphthalene]-2,2'-diol (BN) the experimental EDF spectra show differences due to solvent complexation following the trend in solvent polarity, that are not apparent in the electronic circular dichroism (ECD) or corresponding electronic absorption (EA) spectra. Large experimental EDF spectral magnitudes for BN are seen to peak in regions with no corresponding peaks in the EA spectrum and only a shoulder in the ECD spectrum. This observation indicates that EDF analysis is a new complementary method to conventional ECD analysis of chiral molecules. TD-DFT calculations predict similar EDF peaks as in the experimental EDF spectra, however, the experimentally observed solvation dependent behaviour of the EDF peaks was not reproduced in the calculations. Studies on 6,6'-dibromo-[1,1'-binaphthalene]-2,2'-diol also show similar characteristics in the EDF spectra, though not as pronounced and with different solvent effects. This report thus identifies a new means of chiral molecular structural analysis, hitherto unnoticed, and establishes the use of the dissymmetry factor spectrum as yielding new insight, but at no added cost.
一项利用新开发的电子不对称因子（EDF）光谱分析的研究表明，对于[1,1'-联萘]-2,2'-二醇（BN），实验性EDF光谱显示出由于溶剂络合而导致的差异，其遵循溶剂极性趋势，而这些差异在电子圆二色性（ECD）或相应的电子吸收（EA）光谱中并不明显。BN的实验性EDF光谱的大值在EA光谱中没有相应峰且在ECD光谱中只有一个肩峰的区域达到峰值。这一观察结果表明，EDF分析是对手性分子进行传统ECD分析的一种新的补充方法。含时密度泛函理论（TD-DFT）计算预测出与实验性EDF光谱中相似的峰，然而，计算中并未重现实验观察到的EDF峰的溶剂化依赖性行为。对6,6'-二溴-[1,1'-联萘]-2,2'-二醇的研究在EDF光谱中也显示出类似特征，尽管不那么明显且具有不同的溶剂效应。因此，本报告确定了一种迄今未被注意到的手性分子结构分析新方法，并确立了不对称因子光谱的用途，即能提供新的见解，且无需额外成本。
