Charge transfer complexes between iodine and aromatic aza-compounds. Part 3.—Pyridine and derivatives

Abstract

The substituent effect on charge-transfer equilibria between iodine and meta- and para-substituted pyridines has been studied spectrophotometrically in dichloromethane. A good correlation is observed between the acidity constants of pyridinium ions and the stability constants of charge transfer complexes. The Hammett plot for K_CT gives ρ=–2.34, a value much lower than for protonation equilibria. The results are briefly compared with those previously obtained for styrylpyridines.