Performance of the M06 family of functionals in prediction of the charge transfer transition energies of the naphthalene–TCNE and pyrene–TCNE molecular complexes

The B3LYP and the M06 family of functionals were found to be of nearly equal efficiency for predicting the 13C and 15N NMR chemical shifts (which are ground state properties) of molecular complexes of TCNE with naphthalene and pyrene. But the B3LYP functional could not find any charge transfer (CT) absorption band of the complexes. The M06, M06-2X, M06-HF and M06-L functionals could find two CT absorption bands in CCl4 medium by a TDDFT calculation under the PCM formalism for solvation; the calculated CT transition energies are comparable with the reported experimental values, M06-2X and M06-L agreeing best with experiment.