A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky St. 1, 664033 Irkutsk, Russia.
Department of Chemistry and Biochemistry, Seton Hall University, 400 South Orange Ave., South Orange, NJ 07079, USA.
Int J Mol Sci. 2024 Jul 15;25(14):7733. doi: 10.3390/ijms25147733.
Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon-carbon bonds in the interior of the helical turn of the molecule based on the progressive upfield shift of C resonances toward the center of the helical turn. We now report a comprehensive analysis of the optimized geometry and a comparison of the calculated vs. observed H and C NMR chemical shifts of nineteen representative benzothienoquinoline heterohelicenes. As was initially hypothesized on the basis of the progressive upfield shift of carbon resonances toward the center of the interior helical turn, the present computational study has demonstrated that carbon-carbon bonds indeed have more character and are longer than normal bonds to accommodate the helical twist of the molecule, as expected.
早期的核磁共振研究表明，在含有一个环状氮原子和一个噻吩环的几种杂环庚并[1,2-b]噻吩中，基于 C 共振信号逐渐向螺旋内圈中心移动，分子螺旋内圈中碳-碳键的延长成为可能。我们现在报告了对 19 个代表性苯并噻吩并喹啉杂环庚并[1,2-b]噻吩的优化几何形状的综合分析以及计算与观察到的 H 和 C NMR 化学位移的比较。正如最初基于碳共振信号向螺旋内圈中心逐渐移动的假设，本计算研究表明，碳-碳键确实具有更多的特性，并且比正常的键更长，以适应分子的螺旋扭曲，这是预期的。
