Spectroscopic Studies of Charge-Transfer Complexes of 2,3-Dichloro-5,6-Dicyano-P-Benzo-Quinone

Various aromatic molecules can behave as electron donors and form molecular complexes with electron acceptor molecules such as halogens, mitrocompounds and quinones. Extensive works have been carried out to elucidate the nature of intermolecular interactions in these molecular complexes. Mulliken has developed the theory of the intermolecular CT interactions, which has been applied successfully to the interpretation of the absorption bands characteristic of molecular complexes in various systems . DDQ is a strong electron acceptor having electron affinity 1.9 e.v.. In the present paper, spectrophotometric studies have been carried out for CT complexes of DDQ with p-acetotoluidide, acetanilide, biphenyl and naphthalene, special attention being paid to the appearance of two CT bands. Orgel first reported two bands in the case of methylbenzene complexes of chloranil and 1,2,5-trinitrobenzene. Orgel related the two ionization potentials of the donor molecules to the frequencies of the CT bands.