Oram Binod Kumar, Bandyopadhyay Biman
Department of Chemistry, Malaviya National Institute of Technology Jaipur, Jaipur 302017, India.
Department of Chemistry, Malaviya National Institute of Technology Jaipur, Jaipur 302017, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Apr 5;230:118070. doi: 10.1016/j.saa.2020.118070. Epub 2020 Jan 16.
O-H···O=C Hydrogen bonding (H-bonding) results in spectral shifts in both ν and ν modes. A large number of investigations exist in literature that focuses on how the spectral shifts vary with certain properties of the donors and acceptors. However information on how the magnitude of spectral shift is dictated individually by the donor and acceptor is not yet clear to us. Here, IR spectroscopy in room temperature CCl solution has been used to investigate how ν spectral shifts of ketones in H-bonded complexes with alcohols are influenced by change in donor and acceptor properties. For this purpose 25 number of O-H···O=C H-bonded complexes formed by 5 different ketones and 5 alcohols have been studied. The magnitude of red-shifts shown by the ν bands were found to show systematic trends with changing donor and acceptor species. It was found that for a particular ketone, the magnitude of shift increases monotonically with acidity of the alcohols. Spectral shifts were found to increase in a linear fashion with decreasing p of the donor alcohols. On the other hand, when the alcohol were kept fixed, the spectral shift was found to be dependent on the CO bond strength of the ketones. We found spectral shifts to linearly increase with increasing anharmonicity constant and decreasing dissociation energy of CO bond. Finally, it has been shown that there exist concomitant correlations of the spectral shifts with donor p and acceptor ν anharmonicity constant/bond dissociation energy. The relations have been validated for H-bonded complexes of 1,4-cyclohexanedione with the above mentioned five alcohols.
O-H···O=C氢键作用会导致ν和ν模式下的光谱位移。文献中有大量研究聚焦于光谱位移如何随供体和受体的某些性质而变化。然而，关于光谱位移的大小如何分别由供体和受体决定，我们尚不清楚。在此，利用室温下CCl溶液中的红外光谱来研究与醇形成氢键复合物的酮的ν光谱位移如何受供体和受体性质变化的影响。为此，研究了由5种不同的酮和5种醇形成的25种O-H···O=C氢键复合物。发现ν带所显示的红移大小随供体和受体种类的变化呈现出系统的趋势。结果发现，对于特定的酮，位移大小随醇的酸度单调增加。发现光谱位移随供体醇的p值降低呈线性增加。另一方面，当醇保持固定时，发现光谱位移取决于酮的C=O键强度。我们发现光谱位移随非谐常数的增加和C=O键离解能的降低呈线性增加。最后，研究表明光谱位移与供体p值和受体ν非谐常数/键离解能之间存在相关关系。这些关系已在1,4-环己二酮与上述五种醇的氢键复合物中得到验证。
