Molecular complexes of paraquat with sodium purinates have been investigated spectrophotometrically.All the complexes exhibit one charge transfer band each in the region where neither of the components have any absorption.The stoichiometry of each complexis found to be 1:1 from Job's method.The ionization potentials of the purinate ions have been determined from the position of the CT bands.The stability constants and thermodynamic parameters o the complexes have been determined from the absorption studies on CT bands.The shifts in th position of CT band of PQ-purinate and the variation of its stability constant with substituents are explained in terms of the number of substituents,the ionization of substituents,the mesomeric effect of substituents and the hyperconjugation of substituents in the puring ring.
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