Comparison of acceptor properties for interaction of TCNE and DDQ with some free base porphyrins

Abstract

The interactions of free base porphyrins with tetracyanoethylene and 2,3-dichloro-5,6-dicyanobezoquinone as acceptors result in charge-transfer adducts of composition 2:1 of acceptor to donor, [(acceptor)₂(donor)]. Formation constants, K, as well as the thermodynamic parameters, ΔH°, ΔS°, and ΔG° were determined by UV-Vis titration method for the adducts. Surprisingly, the values of DSº ñ 0 and DHº ñ 0 for TCNE are in contrast to ΔH° á 0 and ΔS° á 0 for DDQ. Negative values of DGº make these interactions favorable in the both cases.

KEY WORDS: DDQ, TCNE, Free base porphyrin, Thermodynamic properties

Bull. Chem. Soc. Ethiop. 2011, 25(1), 127-136.