SPECTROPHOTOMETRIC STUDY OF CO(II), NI(II), CU(II), ZN(II), CD(II) AND PB(II) COMPLEXES WITH SOME CROWN-ETHERS IN DIMETHYLSULFOXIDE SOLUTION USING MUREXIDE AS A METALLOCHROMIC INDICATOR

The complexation reactions between Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions and benzo-15-crown-5, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and 1,10-diaza-18-crown-6 have been studied in dimethylsulphoxide solution at 25-degrees by means of a competitive spectrophotometric method using murexide as a metallochromic indicator. With the exception of Pb(II)(benzo-15-croqn-5)2 the stoichiometry of the resulting complexes was found to be 1 : 1. The formation constants of the complexes were determined, and found to follow the Irving-Williams rule for the cations of the first transition series. It was found that the metal ion-18-crown interactions are strongly dependent on the nature of the substituents on the ring.