Supramolecular structure and substituents effect on the spectral studies of dioxouranium(VI) azodyes complexes

Abstract

Abstract The synthesis of several coordination azo compounds of dioxouranium(VI) heterochelates with bidentate azo compounds derived from 4-alkylphenylazo-5-sulfo-8-hydroxyquinoline (HL n ) ligands, are described. The ligands and structural composition of azo complexes were confirmed and characterized by various physico-chemical techniques. The bonding sites of the azo compounds are deduced from IR and 1 H NMR spectra and the ligands were found to bond to the UO 2 2 + ion in a bidentate fashion. The ligands obtained contain N N and phenolic functional groups in different positions with respect to the quinoline group. IR spectra show that the azo compounds (HL n ) acts as a monobasic bidentate ligand by coordinating via the azo nitrogen atom of azodye ( N N ) and oxygen atom of the phenolic group forming thereby a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The υ 3 frequency of UO 2 2 + has been shown to be an excellent molecular probe for studying the coordinating power of the ligands. The values of υ 3 of the prepared complexes containing UO 2 2 + were successfully used to calculate the force constant, F UO (1n 10 −8 N/A) and the bond length R UO (in A) of the U O bond. A strategy based upon both theoretical and experimental investigations has been adopted. The theoretical aspects are described in terms of the well-known theory of 5d-4f transitions. Wilson’s, matrix method, Badger’s formula, and Jones and El-Sonbati equations were used to calculate the U O bond distances from the values of the stretching and interaction force constants. The most probable correlation between U O force constant to U O bond distance were satisfactorily discussed in term of Badger’s rule and the equations suggested by Jones and El-Sonbati. The effect of Hamette’s constant is also discussed.