Theoretical estimation of pnicogen bonds and hydrogen bonds in small heterocyclic complexes: Red-shifts and blue-shifts ruled by polarization effects

The occurrence of pnicogen bonds (N center dot center dot center dot P) and hydrogen bonds (F center dot center dot center dot H or Cl center dot center dot center dot H) in heterocyclic complexes formed by C2H5N center dot center dot center dot PH3, C2H5N center dot center dot center dot PH2F and C2H5N center dot center dot center dot PH2Cl was investigated at the B3LYP/6-311++G(d,p) level of theory. Analysis of the infrared spectra revealed the appearance of both red and blue shifts for the P-H bonds. However, in the case of the P-F and P-Cl bonds only red shifts were observed. The phenomenology of these vibration modes was interpreted on the basis of the QTAIM atomic radii as well as the contributions of the s and p orbitals determined via NBO calculations. The results of this latter investigation are consistent with the rehybridization theory and the Bent rule for chemical bonding. The charge transfer between N and P was determined in order to verify whether these atoms present an acid or base profile upon the formation of the pnicogen bonds. (C) 2014 Elsevier B.V. All rights reserved.