Isomer recognizing adsorption of palladium(II)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol with diazine derivatives at the toluene-water interface

The isomer recognizing reaction of palladium(II)-2-(5-bromo-2-pyridylazo)-5 -diethylaminophenol-chloride complex (PdLCl) with diazine derivatives at th e toluene-water interface was investigated by a high-speed stirring method. The chloride ion in PdLCl was substituted by a neutral diazine and the PdL +-diazine complex was completely adsorbed at the interface without extracti on into the toluene phase. PdL+-pyridazine derivative complexes showed much higher stability at the interface than pyrimidine and pyrazine derivative complexes. This result could be correlated with the change in the dipole mo ment of the diazine derivative after bonding to PdL+. A linear relationship was obtained between the logarithmic interfacial formation constants (log beta(i)) for PdL+-diazine derivative complexes and the logarithmic ratio of the distribution constant (K-D) to the acid-dissociation constant (K-a) fo r the diazine derivatives. (C) 1999 Elsevier Science B.V. All rights reserv ed.