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The XbondH bond length in XbondH...Y hydrogen bonded complexes is controlled by a balance of two main factors acting in opposite directions. "XbondH bond lengthening" due to n(Y)-->sigma(HbondX) hyperconjugative interaction is balanced by "XbondH bond shortening" due to increase in the s-character and polarization of the XbondH. When hyperconjugation dominates, XbondH bond elongation is reflected in a concomitant red shift of the corresponding IR stretching frequency. When the hyperconjugative interaction is weak and the X-hybrid orbital in the XbondH is able to undergo a sufficient change in hybridization and polarization, rehybridization dominates leading to a shortening of the XbondH and a blue shift in the XbondH stretching frequency.
Alabugin et al. (Sat,) studied this question.