A topological analysis of electron density and chemical bonding in cyclophosphazenes PnNnX2n (X = H, F, Cl; n=2, 3, 4)

The restricted Hartree-Fock method was used to determine the cycle size effects on the geometric parameters of several inorganic templates, cyclophosphazenes PnNnX2n ( X = H, F, Cl; n = 2, 3, 4). A topological analysis of local electronic properties at the electron density critical points of bonds allowed us to quantitatively characterize the chemical bond in cyclophosphazenes and its dependence on the cycle size and substituents at phosphorus. The calculated distributions of the electron density Laplacian and electron pair localization functions revealed the special features of the electronic structure of the nitrogen and phosphorus atoms. These results explain the nature of noncovalent interactions between the P atoms of one cyclophosphazene molecule and the N atoms of the other.