Synyhesis, Crystal Structure And Biological Activity Of N(4)-Substituted Thiosemicarbazones And Their Metal Complexes

Heterocyclic thiosemicarbazones and their metal complexes have generated considerable interest due to varied coordination environments and marked biological activities, notable for antibacterial, antifungal and antitumor activities. In many cases, their biological properties are often related to the donor sequence of the ligands and metal ion coordination. So it is important to study the synthesis, crystal structures and biological activities of heterocyclic thiosemicarbazones and their metal complexes in the finding of new drugs against bacteria and cancer.In this paper, we studied the synthesis, single-crystal structures and biological activities of a series of heterocyclic thiosemicarbazones and their metal complexes. The text has divided into three Chapter which were introduced as follows:Chapter 1 Synthesis, crystal structures and biological activities of N(4)- cyclohexylthiosemicarbazones and their metal complexes Transition metal complexes [Mn(L¹)₂] (1),[Ni(L¹)₂] (2),[Cu₂(L²)₂(CH₃COO)(ClO₄)] (3),[Zn(L2)2] (4),[Mn(L3)2] (5)å’Œ[Ni(L3)2] (6) where HL1 = 2-acetylpyridine N(4)-cyclohexylthiosemicarbazone, HL² = 2-benzoylpyridine N(4)-cyclohexylthiosemicarbazone, HL3 = 2-acetylpyrazine N(4)-cyclohexyl thiosemicarbazone, have been synthesized and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction studies. Biological studies, carried out in vitro against bacteria and K562 leukemic cell line, respectively, have shown that the free ligands (HL1, HL2 and HL3) and their corresponding complexes show distinct differences in the biological properties. In addition, the complexes all showed higher biological activity than their separate ligands. Chapter 2 Synthesis, crystal structures and biological activities of N(4)- phenylthiosemicarbazones and their diorganotin(IV) complexesFour diorganotin(IV) complexes [(Me)₂Sn(L⁴)(CH₃COO)]?CH3CH2OH (7), [(Ph)2Sn(L4)(CH3COO)]?CH3CH2OH (8), [(Me)2Sn(L5)Cl] (9) and [(Ph)₂Sn(L⁵)(CH₃COO)] (10) where HL⁴=2-benzoylpyridine N(4)-phenylthiosemicarbazone, HL5=2-acetylpyrazine N(4)-phenylthiosemicarbazone have been synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction studies. Biological studies, carried out in vitro against bacteria and K562 leukemic cell line, respectively, have shown that the free ligands and their corresponding complexes show distinct differences in the biological properties. In addition, HL4 shows much lower IC50 value than HL5,and phenyl diorganotin complexes of the same ligand show enhanced antitumor activity than that of their corresponding methyl diorganotin derivatives.Chapter 3 Synthesis, crystal structures and biological activities of 2-thiophene N(4)-methylthiosemicarbazone and its Ag(I) complex2-Thiophene N(4)-methylthiosemicarbazone (HL⁶) and its Ag(I) complex of formula [Ag6(L)6?4DMF] (11) have been synthesized and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction studies. The silver(I) complex 11 is an unusual hexanuclear cluster with 6 silver atoms in different environments. Biological studies, carried out in vitro against bacteria, fungi and SMMC-7721 liver cancer cell line, respectively, have shown that the free ligand and its silver(I) complex show distinct differences in the biological property.