The molecules cyanoacetylene and dicyanoacetylene detected in the atmosphere of Saturn’s largest moon Titan were investigated in superacidic media XF/MF₅ (X = H, D; M = As, Sb), XF/GeF₄, and XF/BF₃. Cyanoacetylene is obtained as a monoprotonated salt, while only the diprotonated salt of dicyanoacetylene has been isolated. The salts were characterized by vibrational spectroscopy, NMR spectroscopy, and single-crystal X-ray diffraction. The protonations lead to a significant shortening of the C≡N bond. The salts of [C₃HXN][SbF₆] (X = H, D) show very rare coupled oscillations in vibrational spectroscopy. The experimental results are discussed together with quantum chemical calculations at the M062X/aug-cc-pVTZ level of theory. The −M and −I effects of the C≡N moiety decrease by protonation of the nitrile moiety.

中文翻译：

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超酸性介质中的空间分子 ─ 单质子化氰基乙炔和二质子化二氰基乙炔的合成与结构


在土星最大的卫星泰坦的大气中检测到的分子氰乙炔和二氰基乙炔是在超酸性介质 XF/MF₅ （X = H， D;M = As， Sb）、XF/GeF₄ 和 XF/_{BF 3}。氰基乙炔以单质子化盐的形式获得，而仅分离出二氰基乙炔的二质子化盐。通过振动光谱、NMR 光谱和单晶 X 射线衍射对盐进行表征。质子导致 C≡N 键显着缩短。[C₃HXN][SbF₆] （X = H， D） 的盐在振动光谱学中显示出非常罕见的耦合振荡。实验结果与 M062X/aug-cc-pVTZ 理论水平的量子化学计算一起讨论。C≡N 部分的 −M 和 −I 效应因丁腈部分的质子化而降低。