T. Premkumar, S. Govindarajan
Apr 8, 2002
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0
Influential Citations
27
Citations
Journal
Thermochimica Acta
Abstract
Abstract New hydrazinium hydrogen-4,5-imidazoledicarboxylate (N 2 H 5 Himdc), its monohydrate, N 2 H 5 Himdc·H 2 O, (H 2 imdc=4,5-imidazoledicarboxylic acid) and the metal complexes of the type M(imdc)0.5N 2 H 4 ·H 2 O, where M=Mn,Co or Cd and M(imdc)N 2 H 4 ·H 2 O, where M=Ni or Zn have been prepared. The compounds have been characterised by analytical, electronic and IR spectral and thermal studies. Electronic spectral data suggest that the Co and Ni complexes are of spin-free (high spin) type with octahedral geometry. The IR absorption bands of NN stretching in the range 970–960 cm −1 unambiguously prove the bidentate bridging nature of the N 2 H 4 ligands. IR spectra also confirm the unidentate coordination behaviour of carboxylate ( ν asy =1570 cm −1 and ν sym =1390 cm −1 ) groups of the imidazoledicarboxylate dianion. Simultaneous TG and DTA of the free acid show a single-step complete endothermic (281 °C) decomposition whereas its anhydrous and hydrated hydrazinium salts show endotherm followed by exotherm decomposition. All the metal complexes undergo endothermic decomposition around 100 °C with the loss of hydrazine and water, via the metal 4,5-imidazoledicarboxylate which further decomposes exothermically in the range 110–560 °C to give the respective metal oxide as the end product.