Department of Chemistry, Annamalai University, Annamalainagar 608002, Tamil Nadu, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 Oct 15;81(1):363-71. doi: 10.1016/j.saa.2011.06.024. Epub 2011 Jun 22.
Some novel N-nitroso oxime derivatives were synthesized and characterized by (1)H, (13)C, (1)H-(1)H and (1)H-(13)C COSY NMR spectra. The spectra of all these N-nitroso oximes reveal the presence of two isomers labelled as E (-NOH group is anti to N-N=O moiety) and Z (-NOH group is syn to N-N=O moiety) in solution and the coupling constants ruled out the possibility of normal chair conformation. From the theoretical studies and coupling constant values it was found that both E (major) and Z (minor) isomers of N-nitroso oximes exist as an equilibrium mixture of CA and boat conformation (B(1)) and this was also supported by DFT calculation. The photophysical properties of these oxime derivatives were studied and the observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed due to the presence of non-chair conformation of N-nitroso oxime derivatives.
一些新型 N-亚硝基肟衍生物被合成并通过 (1)H、(13)C、(1)H-(1)H 和 (1)H-(13)C COSY NMR 光谱进行了表征。所有这些 N-亚硝基肟的光谱都表明存在两种异构体，分别标记为 E（-NOH 基团与 N-N=O 部分反式）和 Z（-NOH 基团与 N-N=O 部分顺式），在溶液中，且偶合常数排除了正常椅式构象的可能性。从理论研究和偶合常数值可以发现，N-亚硝基肟的 E（主要）和 Z（次要）异构体都以 CA 和船型构象（B(1)）的平衡混合物存在，这也得到了 DFT 计算的支持。这些肟衍生物的光物理性质也进行了研究，观察到的较低荧光量子产率可能是由于非辐射去活速率常数的增加。这归因于 N-亚硝基肟衍生物存在非椅式构象。
