Lanthanum(III) and praseodymium(III) complexes with isatin thiosemicarbazones

Ten new lanthanum(III) and praseodymium(III) complexes of the general formula Na[La(L)₂H₂O] (Ln = La(III) or Pr(III); LH ₂ = thiosemicarbazones) derived from the condensation of isatin with 4-phenyl thiosemicarbazide, 4-(4-chlorophenyl) thiosemicarbazide, 4-(2-nitrophenyl) thiosemicarbazide, 4-(2-bromophenyl) thiosemicarbazide and 4-(2-methylphenyl) thiosemicarbazide, have been synthesized in methanol in presence of sodium hydroxide. The XRD spectra of the complexes were monitored to verify complex formation. The complexes have also been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, ¹H and ¹³C NMR spectral studies. Thermal studies of these complexes have been carried out in the temperature range 25-800°C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of Ln₂O₃ as the end product. The Judd-ofelt intensity parameter, oscillator strength, transition probability, stimulated emission cross section for different transitions of Pr³⁺ for 4-phenyl thiosemicarbazones have been calculated.