Continuum in H-bond and Other Weak Interactions (X–Z···Y): Shift in X–Z Stretch from Blue Through Zero to Red

Karir, G and Jemmis, ED (2020) Continuum in H-bond and Other Weak Interactions (X–Z···Y): Shift in X–Z Stretch from Blue Through Zero to Red. In: Journal of the Indian Institute of Science, 100 (1). pp. 127-133.

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Abstract

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.

Item Type:	Journal Article
Publication:	Journal of the Indian Institute of Science
Publisher:	Springer
Additional Information:	The copyright for this article belongs to Springer.
Keywords:	Bond length; Charge transfer; Doppler effect; Hydrogen bonds; Monomers; Red Shift, Blue shifting; Electron pair donors; Electron-rich; General trends; Hyperconjugation; Main-group elements; Stretching frequency; Weak interactions, Blue shift
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	08 Feb 2023 08:41
Last Modified:	08 Feb 2023 08:41
URI:	https://eprints.iisc.ac.in/id/eprint/80058

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