A Density Functional Approach toward Structural Features and Properties of C20 and its Complexes with C2X4, C2X2 (X = H, F, Cl, Br) for Synthesis Application

The complexes between C20 and C2X4, C2X2 (X = H, F, Cl, Br) have been studied theoretically at the B3LYP/6-311G (d,p) level. The calculations include the optimized geometries, the interaction energies, aromaticity and thermodynamic. The interaction energies ranging from -60 to -101 kcal/mol and being ordered as: X = F> Cl > Br. Natural bond orbital (NBO) analysis has been performed on all geometries. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results, and indicate that, in all the molecules HOMO-1 → LUMO transition has the major contribution in the most intensity electronic transition.