Relationships between Interaction Energy and Electron Density Properties for Homo Halogen Bonds of the [(A)nY-X•••X-Z(B)m] Type (X = Cl, Br, I)

Relationships between interaction energy (E-int) and electron density properties at the XX bond critical point or the d(XX) distance were established for the large set of structures [(A)(n)Y-XX-Z(B)(m)] bearing the halogen bonds ClCl, BrBr, and II (640 structures in total). The best estimator of E-int is the kinetic energy density (G(b)), which reasonably approximates the whole set of the structures as -E-int = 0.128G(b)(2) - 0.82G(b) + 1.66 (R-2 = 0.91, mean absolute deviation 0.39 kcal/mol) and demonstrates low dispersion. The potential and kinetic energy densities, electron density, and the d(XX) distance behave similarly as estimators of E-int for the individual series ClCl, BrBr, and II. A number of the E-int(property) correlations are recommended for the practical application in the express estimates of the strength of the homo-halogen bonds.