Synthesis, crystal structure and biological activity of thiophene-2-carboxaldehyde thiosemicarbazone and its tin complexes

Thiophene-2-carboxaldehyde thiosemicarbazone, C4H3S–CHN–NH–C(S)NH2 (tctscH) obtained by the condensation reaction of thiophene-2-carboxaldehyde with thiosemicarbazide forms SnPh2Cl(tctsc), 1 and SnCl2(tctsc)2, 2 with SnPh2Cl2 and SnPhCl3 in 1:1 and 1:2 tin:ligand molar ratios, respectively. The crystal structure determination shows that in both 1 and 2, tctscH is deprotonated and functions as an anionic bidentate ligand, co-ordinating to the tin atom through its azomethine-N and thiol-S atoms. The geometry about the tin atom for complex 1 is distorted trigonal bipyramidal whereas for complex 2 is distorted octahedral. Note that dephenylation occurs during the formation of complex 2. Fungitoxicity and cytotoxicity of the two tin complexes and tctscH have been evaluated and the biological activity is more remarkable in complex 1 in comparison to the other.