Performance of the M06 family of functionals in predicting the charge transfer transition energies of molecular complexes of TCNE with a series of methylated indoles

Abstract

Ground state intermolecular interactions in the molecular complexes of TCNE with a series of methylated indoles have been predicted with almost equal efficiency by the B3LYP and the M06 family of functionals. However, TDDFT calculation with the B3LYP functional failed to find any charge transfer (CT) absorption band of the complexes while each of the functionals M06, M06-2X, M06-HF and M06-L succeeded; the calculated CT transition energies vary with the calculated vertical ionization potentials of the indoles, complying with Mulliken’s theory of charge transfer complexes and are fairly close to reported experimental values.