The azo–hydrazo tautomerism of four model azo dyes in the solid state is investigated by multinuclear solid-state nuclear magnetic resonance (SS-NMR) spectroscopy, X-ray diffraction and quantum-chemical calculations. The measurement of ¹⁵N SS-NMR spectra is the most straightforward way to determine the tautomeric state of solid azo compounds. Unfortunately, the sensitivity of these nuclei for SS-NMR is very low and the acquisition of ¹⁵N spectra in a reasonable time may be challenging. It is demonstrated that a natural abundance of almost 100% of another nitrogen isotope, ¹⁴N, can be exploited for the investigation of the tautomerism. Indirect detection of ¹⁴N nuclei via protons is an elegant approach for the rapid and unequivocal determination of the tautomeric form. Furthermore, a comparison of experimental carbon SS-NMR chemical shifts with those obtained in solution or by quantum-chemical computations can be used for the same purpose.

通过多核固态核磁共振（SS-NMR）光谱，X射线衍射和量子化学计算研究了固态的四种模型偶氮染料的偶氮-偶氮互变异构现象。¹⁵ N SS-NMR光谱的测量是确定固体偶氮化合物互变异构状态的最直接方法。不幸的是，这些核对SS-NMR的敏感性非常低，在合理的时间内获取¹⁵ N光谱可能具有挑战性。结果表明，可以利用几乎100％的另一种氮同位素¹⁴ N的自然丰度来研究互变异构现象。间接检测¹⁴通过质子的N核是一种快速而明确地确定互变异构形式的优雅方法。此外，可以将实验碳SS-NMR化学位移与溶液或通过量子化学计算获得的碳位移进行比较。