New look at the Badger-Bauer rule: Correlations of spectroscopic IR and NMR parameters with hydrogen bond energy and geometry. FHF complexes

Abstract In this work correlation dependencies between hydrogen bond energy Δ E for complexes with F H⋯F hydrogen bond and their spectroscopic characteristics of the IR and NMR spectra are presented. We considered 26 complexes in a wide hydrogen bond energy range 0.2–47 kcal/mol. For each complex we calculated complexation energy (MP2/6-311++G(d,p)), IR spectroscopic parameters (FH stretching frequency ν , FH stretching frequency in local mode approximation ν LM at MP2/6-311++G(d,p) level) and NMR parameters (chemical shift of hydrogen δ H and fluorine nuclei δ F , Nuclear Independent Chemical Shielding and spin-spin coupling constants 1 J FH , 1h J H...F , 2h J FF at B3LYP/pcSseg-2 level). It was shown that changes of parameters upon complexation, i.e. changes of the stretching frequency in local mode approximation Δ ν LM , change of the proton chemical shift Δ δ H and change of the absolute value of spin-spin coupling constant 1 J FH could be used for estimation of corresponding hydrogen bond strength. Furthermore, we build correlation dependencies between abovementioned spectroscopic characteristics and geometric ones, such as the asymmetry of bridging proton position q 1  = 0.5·( r FH – r H…F ).