Abstract:
Ab initio MP4/Aug-cc-pvDZ//MP2/6-311++g(d,p) level interaction energy (Eint) and molecular
electrostatic potential analysis (MESP) of a large variety of non-covalent intermolecular complexes, viz. tetrel,
chalcogen, pnicogen, halogen, hydrogen, dihydrogen and lithium bonded complexes have been reported. The
electronic changes associated with the non-covalent complex formation is monitored in terms of MESP minimum
(Vmin) in the free and complexed states of the donor and acceptor molecules as well as in terms of MESP at
the donor and acceptor atoms (Vn) of the free monomers and complexes. The change in Vmin or Vn on the donor
molecule ( Vmin(D) or Vn(D)) during complex formation is proportional to its electron donating ability while
such a change on the acceptor molecule ( Vmin(A) or Vn(A)) is proportional to its electron accepting ability.
Further, the quantities Vmin = Vmin(D) − Vmin(A) and Vn = Vn(D) − Vn(A) have shown strong
linear correlations with Eint of the complex (Eint values fall in the range 0.7 to 46.2 kcal/mol for 54 complexes)
and suggest that the intermolecular non-covalent interactions in a wide variety of systems can be monitored
and assessed in terms of change in MESP due to complex formation in the gas phase. With the incorporation
of solvent effect in the calculation, charged systems showed significant deviations from the linear correlation.
The MESP based analysis proposes that the large variety of intermolecular non-covalent complexes considered
in this study can be grouped under the general category of electron donor-acceptor (eDA) complexes
