Synthesis, spectral, thermal, solid state d.c. electrical conductivity, fluorescence and biological studies of lanthanum(III) and thorium(IV) complexes of 24-membered macrocyclic triazoles

A series of La(III) and Th(IV) complexes have been synthesized by template condensation of 2,6-diformyl-4-methylphenol, bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)alkanes and La(NO3)(3)center dot 6H(2)O/Th(NO3)(4)center dot 5H(2)O in 2 : 2 : 1 molar ratio in ethanol. These complexes were characterized by elemental analyses, magnetic susceptibility, molar conductance, spectral (IR, UV-Vis, H-1-NMR, FAB-mass), thermal, fluorescence and solid state d.c. electrical conductivity studies. The complexes are insoluble in water but soluble in DMF and DMSO. The observed molar conductance values indicate non electrolytes. Elemental analyses suggest 1 : 1 stoichiometry, [La(LI-IV)(NO3)(H2O)(2)]center dot 3H(2)O and [Th(LI-IV)(NO3)(2)(H2O)(2)]center dot 3H(2)O. Spectroscopic studies indicate that coordination occurs through phenolic oxygen after deprotonation, nitrogen of azomethine group and bridging bidentate nitrates. The solid state d.c. electrical conductivity indicates semiconducting nature. All the Schiff bases and their La(III) and Th(IV) complexes were evaluated for biological properties; some compounds show promising results.