INVESTIGATIONS ON THE CHARGE-TRANSFER INTERACTION OF PHENOLS WITH TETRACYANOETHYLENE (TCNE)

The donor properties of some phenol derivatives were determined by measuring the UV/Vis spectra of their CT complexes with tetracyanoethylene in 1,2-dichloroethane and acetonitrile at room temperature. The ionization potentials of the phenolic compounds have been calculated by using the longest visible charge-transfer absorption of the donor-acceptor complex by linear correlation analysis. The charge-transfer spectra are discussed in dependence on the ring substituents in terms of electronic and steric factors. Increasing donor strength of the substituents decreases the ionization potential of the phenols as demonstrated by an LFE relationship using the Hammett constants. However, ortho donor substituents enhance the donor strength of the aromatic ring as well.