Abstract
Ab initio calculations were carried out to investigate the interaction between para-substituted pyridines (X-C5H4N, X=NH2, CH3, H, CN, NO2) and OCS. Three stable structures of pyridine.OCS complexes were detected at the MP2=full/aug-cc-pVDZ level. The A structure is characterized by N…S chalcogen bonds and has binding energies between −9.58 and −12.24 kJ/mol. The B structure is bonded by N…C tetrel bond and has binding energies between −10.78 and −11.81 kJ/mol. The C structure is characterized by π-interaction and has binding energies between −10.76 and −13.33 kJ/mol. The properties of the systems were analyzed by AIM, NBO, and SAPT calculations. The role of the electrostatic potential of the pyridines on the properties of the systems is outlined. The frequency shift of relevant vibrational modes is analyzed.
Highlights
Hydrogen bonds, without doubt, are the most studied intermolecular interactions today [1,2].Other molecular complexes discovered 150 years ago, have received considerably less attention
They have been classified into halogen bonds where B is a halogen [5,6,7,8,9,10,11,12,13,14,15], chalcogen bonds where B = O, S, Se [16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34], and more recently, tetrel bonds where B = C, Si [35,36,37,38,39,40,41,42]. These bonds are unusual in that they involve a close approach of two electronegative atoms such as Cl, O, C on the one hand, and Y atoms such as N on the other hand. This peculiar bond formation was discussed by Politzer et al [43,44,45] who showed that halogen atoms carry partial negative charges, they have a region of positive electrostatic potential at the head of the halogen atom in the opposite direction of the XB axis
As outlined in a recent work [46], the negative electrostatic potential at the N-atom of substituted pyridines is very sensitive to the substituents, decreasing in the order NH2 > CH3 > H > F > CN > NO2 which is the order of the p.Hammett constants (−0.660, −0.170, 0.062, 0.660, 0.778) [51]
Summary
Without doubt, are the most studied intermolecular interactions today [1,2].Other molecular complexes discovered 150 years ago, have received considerably less attention. These bonds are unusual in that they involve a close approach of two electronegative atoms such as Cl, O, C on the one hand, and Y atoms such as N on the other hand This peculiar bond formation was discussed by Politzer et al [43,44,45] who showed that halogen atoms carry partial negative charges, they have a region of positive electrostatic potential at the head of the halogen atom in the opposite direction of the XB axis.
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