Charge redistribution effect on the properties of charge transfer complexes HnR?XY and HnR?X2 (X, Y = F, Cl, Br, I; R = O, S, N, P)

Abstract

Systematic studies on structures, energies, charge transfer, dipole moments, and ionic character of a series of weakly bonded charge transfer (CT) complexes (D⋅AB, D = H2O, H2S, NH3, PH3, AB = F2, Cl2, Br2, I2, BrCl, IBr, ClF, ICl, BrF, IF) have been carried out by the hybrid Hartree–Fock density functional theory (HF-DFT) method, where those results are validated by available experimental and theoretical investigations. Employing the Hohenberg–Kohn theorem, the property of a multicomponent system is formulated with contributions from both component properties and the charge redistribution (CR) effect, which describes the electronic coupling between components. For any property of a multicomponent system, provided that the intercomponent coupling is weak enough, the first-order approximation can be applied, which yields a linear correlation of the component contribution to the CR effect. In fact, this kind of linear relationship can be evidenced by all the studied properties including the geometry, energy, charge transfer, dipole moment, and ionic character of all 40 complexes. This approximation quantitatively describes the relative contribution of the components to a given property, which shows the same tendency in a series of complexes. Based on the investigations of the CT effect on the intermolecular bond energy and the total dipole moment, it has been found that the principal bonding character of the title complexes was ascertained to be ionic with the exception of the F2 complexes, which agrees well with the calculated ionic character. The CT effect, though small in a quantitative aspect, is directly connected to various kinds of system properties. The effectiveness and consistency of the present type of calculations in multicomponent systems may allow their wider applications in the study of intermolecular interactions. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 327–338, 2001