DISSOCIATION-CONSTANTS OF 2-THIOURACIL AZO-COMPOUNDS AND THE STABILITY-CONSTANTS OF THEIR TRANSITION-METAL COMPLEXES

The dissociation constants of the synthesized 2-thiouracil azo compoun ds were evaluated by potentiometric and spectrophotometric methods. Al l the compounds gave one pK value except the 3-Cl compound that gave t wo values. The data were explained from the electronic character of th e substituents views. No regular trend is obtained on relating both pK (L) or logK(c) with the Hammett constant values. In solution, the mode of interaction between the metals and the ligands is mainly of pi-cha racter. The plot of log K-1 versus pK(L) is a straight line with a sim ilar mode of bonding.