We review the variation of X–Z stretching frequency in the formation of Z-bonds (X–Z···Y, Z = H, or other main group element). Majority of hydrogen bonds (H-bonds) occur between a strongly polar X–H bond and an electron pair donor (H-bond acceptor) Y and show a red shift in the X–H stretch. In very weak H-bonds, there are several instances where the X–H bond is blue shifted. We show that X–H shifts span a continuum going from red through zero to blue; there is nothing improper or anti about H-bonds that are blue shifted. Other Z-bonds bring more factors in deciding the blue and red shift. When negative hyperconjugation in the uncomplexed monomer outweighs the charge transfer from incoming electron-rich species Y during the formation of X–Z···Y (Z = halogen, chalcogen, etc.), it leads to blue shifting X–Z bond. In the absence of negative hyperconjugation in the monomer, X–Z bond length elongation (red shift) is almost always observed on complexation with Y. In an X–Z···Y interaction, the detailed nature of the fragment X has the major influence on the way Z and Y control bond length elongation/contraction. The general trend in the magnitude of blue shift amongst various weak interactions was observed to be in the following order: halogen > chalcogen > hydrogen > pnicogen bonding.

中文翻译：

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氢键的连续体和其他弱相互作用（X-Z···Y）：X-Z 拉伸从蓝色到零到红色的转变

我们回顾了形成 Z 键（X-Z…Y，Z = H 或其他主族元素）时 X-Z 伸缩频率的变化。大多数氢键（H 键）发生在强极性 X-H 键和电子对供体（H 键受体）Y 之间，并在 X-H 拉伸中显示红移。在非常弱的 H 键中，有几种情况下 X-H 键发生蓝移。我们表明 X-H 位移跨越从红色到零再到蓝色的连续区；蓝移的 H 键没有任何不当或反感。其他 Z 键在决定蓝移和红移方面带来更多因素。在 X–Z…Y（Z = 卤素、硫属元素等）的形成过程中，当未复合单体中的负超共轭超过来自进入的富电子物质 Y 的电荷转移时，它会导致 X–Z 键蓝移。在单体中没有负超共轭的情况下，在与 Y 络合时几乎总是观察到 X-Z 键长伸长（红移）。在 X-Z…Y 相互作用中，片段 X 的详细性质具有主要Z 和 Y 控制键长伸长/收缩的方式的影响。观察到各种弱相互作用之间蓝移幅度的一般趋势按以下顺序排列：卤素 > 硫属元素 > 氢 > pnicogen 键合。