Nature and Strength of the π‐Hole Chalcogen Bonded Complexes between Substituted Pyridines and SO3 Molecule

Abstract

AbstractA theoretical study has been carried out on the π‐hole based chalcogen bonding interaction between SO3 and various pyridines (XC5H4N), at the MP2=full/aug‐cc‐pVTZ level, to obtain a better insight into the nature and strength of N…S bond. Our calculations predict two different types of chalcogen bonded complexes: (1) Type‐A complex is formed via lone pair‐ π‐hole (N…S) interaction, and (2) Type‐B complex is stabilized through π‐hole‐π‐electron interaction. The binding energy of the Type‐A complexes varies between −109.78 and ‐81.56 kJ/mol whereas it ranges between −28.93 and −17.82 kJ/mol for Type‐B complexes. The nature of the N…S bond and the changes in its properties on the influence of electron donating and electron withdrawing substituents have been discussed with the help of various computational tools like AIM, NCI, SAPT and NBO analysis. The binding energy of the Type‐A complexes are found to correlate with the basicity parameters such as PA and Vs,min of the substituted pyridines. The binding energies of the pyridine complexes with SF2, SO2, CS2 and OCS are also computed for finding the effect of variation of Vs,max value of the S‐atom on the binding energy. The 2nd order hyperconjugation interaction energy between LP(N) and σ*(S−O)/LP*(S) is well correlated to the binding energy as: −ΔE=0.11E(2) −20.08. The variation in the bond distances and their corresponding vibrational frequencies of both the interacting partners (XC5H4N and SO3) are discussed in detail.