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.
A 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.
Ab initio calculation at the MP2/aug-cc-pVTZ level has been performed on the π-hole based N … Si tetrel bonded complexes between substituted pyridines and H 2 SiO. The primary aim of the study is to find out the effect of substitution on the strength and nature of this tetrel bond, and its similarity/difference with the N … C tetrel bond. Correlation between the strength of the N … Si bond and several molecular properties of the Lewis acid (H 2 SiO) and base (pyridines) are explored. The properties of the tetrel bond are analyzed using AIM, NBO, and symmetry-adapted perturbation theory calculations. The complexes are characterized with short N … Si intermolecular distances and high binding energies ranging between À 142.72 and À 115.37 kJ/ mol. The high value of deformation energy indicates significant geometrical distortion of the monomer units. The AIM and NBO analysis reveal significant coordinate covalent bond character of the N•••Si π-hole bond. Sharp differences are also noticed in the orbital interactions present in the N•••Si and N•••C tetrel bonds.
Ab
initio MP2/aug-cc-pVTZ calculations have been carried out in
order to study the nature of P···Cl halogen bonding
interaction between a phosphorus atom in an aromatic ring in para-substituted
phosphabenzene (PPBZ) and ClF molecule. The interaction of PPBZ with
ClF results in two different types of complexes: (i) complex formation
through the chlorine-shared halogen bond (T1-X-PPBZ·ClF) and
(ii) complex formation
via
halogen−π
interaction (T2-X-PPBZ·ClF). T1-X-PPBZ·ClF complexes are
found to be more stable than the T2-X-PPBZ·ClF complexes. This
work also presents a general criterion to distinguish a chlorine-shared
halogen bond from a traditional halogen bond and sheds light on the
formation of the chlorine-shared halogen bond. The binding energy
of T1-X-PPBZ·ClF complexes correlates well with the negative
electrostatic potential of the P atom and PA value of the substituted
PPBZ. The properties of both T1-X-PPBZ·ClF and T2-X-PPBZ·ClF
complexes are analyzed using atom-in-molecule, natural bond orbital,
and symmetry-adapted perturbation theory calculations. The variation
of the Cl–F bond distances and the redshifts of the ν(ClF)
vibration resulting from the interaction with PPBZs are discussed.
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