Self-assembled Transition Metal Coordination Frameworks of ...

Chapter 2 _ 7 f __ i
2.3. Results and discussion
The syntheses of carbohydrazones and thiocarbohydrazones were done by
condensation reaction in acid medium. The ratio of reagents, solvent, pH of the
medium, etc are found affecting the reactions considerably. The syntheses of H2L2
[ll] and HZLS have been reported [4]. HZLS was prepared according to reported
procedure except that a 2 h refluxion could yield 67%, against 70% yield for 60 h. The
syntheses of thiosemicarbazones HL7 and HL8 were done by adapting a reported
procedure of Scovill [20]. 4-Methyl-4-phenyl-3-thiosemicarbazide was prepared as
reported previously [20]. The synthesis of HI] and HL8 from 4-methyl-4-pheny1-3­
thiosemicarbazide comprises two processes namely condensation and transamination.
The condensation reaction of 4-methyl-4-phenyl-3-thioseinicarbazide with 2­
benzoylpyridinc or quinoline-2-carbaldehyde results by the removal of a water
molecule and transamination process involves the replacement of N-methylaniline
with pyrrolidine. However both these were achieved in a single step reaction without
any addition of acid, but in low yield compared to two-step reactions. The
thiocarbohydrazones and thiosemicarbazones prepared are all yellow in color but the
carbohydrazones all are found to be colorless. All compounds except H2L° are soluble
in chloroform and DMSO. HZL6 is readily soluble in DMF only and soluble in
methanol slightly on heating.
2.3. I . IR spectral studies
The [R spectra of all compounds were recorded in the 4000-400 cm" range.
(Thio)carbohydrazoncs, in principle, can exhibit (thio)ketone-(thio)enol tautomerism.
Also, since the spectra are very much rich with bands, a comparison of spectra of all
carbohydrazones and thiocarbohydrazones are also found useful to assign these bands,
which are listed in Table 2.1.
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