Supramolecular structures and stereochemical versatility of azoquinoline containing novel rare earth metal complexes

Rare earth complexes of 5-(phenylazo)-8-hydroxyquinoline (HL) of composition [M(L)2X·H2O] [where M = La, Ce, Pr, Nd and X = NO3− or NCS−] have been prepared and characterized on the basis of their chemical analyses, 1H NMR, magnetic measurements, conductance, and visible and IR spectral data. Composition, conductance and IR spectral data of the complexes show that the HL acts as a bidentate monobasic ligand. The visible spectra of Pr3+ and Nd3+ show characteristic f–f transitions, and the nephelauxetic effect (1 − β) of these transitions has been evaluated. These data indicate the weak involvement of the 4f orbitals in complex formation.