Theoretical studies on the optimal X (OH) _3-H _2O (X = N, P, Sb) complexes: Interaction energies and topological analysis of the electronic density

摘要

We study the interaction of N (OH) _3, P (OH) _3 and Sb (OH) _3 with a water molecule for which triply hydrogen-bonded complexes have been found. We obtain interaction energies and analyze the electronic density through Atoms-in-Molecules approach. Including the recent result for As (OH) _3, MP_2 CBS extrapolated interaction energies are 9.37, 10.06, 10.67 and 10.72 kcal/mol for N (OH) _3, P (OH) _3, As (OH) _3 and Sb (OH) _3, respectively. CASSCF (6,6)+CASPT2 calculations reveal a multireference character for the complexes yielding interaction energies from 6.4 to 14 kcal/mol. AIM analysis shows three intermolecular bond critical points confirming the hydrogen bonds. NBO atomic charges show reveal the dominant dipole-dipole nature of the intermolecular interactions.