Photochemical reactions of group VIB metal carbonyls with heterocyclic Schiff bases derived from 4-amino -3-hydrazino-5-mercapto-1,2,4-triazole

The new complexes, M(CO)₅(Schiff base) [M?=?Cr; 1, Mo; 2, W; 3, Schiff base?=?4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole, SAHMT, a; 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 2HNAHMT, b; 4-(3-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 3HBAHMT, c; 4-(4-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 4HBAHMT, d; 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 5BrSAHMT, e; were synthesized by photochemical reaction of metal carbonyls M(CO)₆ (M?=?Cr, Mo, W) with new heterocyclic Schiff bases derived from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, a–e. The ligands and complexes have been characterized by elemental analysis, EI-mass spectrometry, FT-IR, ¹H and ¹³C-{¹H}-NMR spectroscopy. The spectroscopic studies show that Schiff bases, a–e, are monodentate and coordinate via azomethine N donor to the central metal atom in M(CO)₅(Schiff base) (M?=?Cr, Mo, W).     

Synthetic, structural and biological studies of organotin(IV) complexes of schiff bases derived from pyrrol-2-carboxaldehyde

Some new organotin(IV) complexes having general formulae R₂MCl[L] and R₂M[L]₂ were synthesized by the reactions of Me₂MCl₂ with Schiff bases [5-Mercapto-4-(pyrrolcarboxalideneamino)-s-triazole, 5-Mercapto-3-methyl-4-(2-pyrrolcarboxalideneamino)- s-triazole, 3-Ethyl-5-mercapto-4-(2-pyrrolcarboxalideneamino)-s-triazole] in 1:1 and 1:2 molar ratios. All of the compounds were characterized by elemental analysis, molar conductance, IR, UV, ¹H, ¹³C and ¹¹⁹Sn NMR spectral studies. The IR and ¹H NMR spectral data suggest the involvement of azomethine nitrogen in coordination with the central metal atom. With the help of the above-mentioned spectral studies, penta and hexacoordinated environments around the central metal atoms in the 1:1 and 1:2 complexes, respectively, have been proposed. Finally, the free ligands and their metal complexes were tested in vitro against some pathogenic bacteria and fungi to assess their antimicrobial properties.     

New complexes of Ni(II) and Cu(II) with Schiff bases functionalised with 1,3,4-thiadiazole: spectral,magnetic, biological and thermal characterisation

Schiff bases obtained by the condensation of 2-amino-5-mercapto-1,3,4-thiadiazole with 2,4-pentandione or 1-phenyl-1,3-butandione were synthesized and characterized in order to obtain polydentate ligands HL¹ and HL², respectively. The complexes with these ligands of the type M(L)Cl·nH₂O [(1) M:Ni, L:L¹, n = 0.5; (3) M:Ni, L:L², n = 0.5]; [(2) M:Cu, L:L¹, n = 1; (4) M:Cu, L:L², n = 0] were also synthesized and characterized. The modifications evidenced in IR spectra of complexes were correlated with the presence of monodeprotonate Schiff bases. The electronic spectra display the characteristic pattern of square-planar stereochemistry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the new complexes exhibited variable antimicrobial activity. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Schiff bases and complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed.     

Synthesis, physicochemical investigation and biological studies of Zinc(II) complexes with 1,2,4-triazole Schiff bases

A series of metal complexes of Zn(II) have been synthesized with newly synthesized biologically active 1,2,4-triazole Schiff bases derived from the condensation of 3-substituted-4-amino-5-mercapto-1,2,4-triazole with 8-formyl-7-hydroxy-4-methylcoumarin. The structure of the complexes has been proposed in the light of elemental analyses, spectroscopic data (IR, UV-Vis, ¹H NMR and FAB-mass), thermal studies. Electrochemical study of the complexes is also reported. All the complexes are soluble to limited extent in common organic solvents but soluble to larger extent in DMF and DMSO and are non-electrolytes in these two solvent. All these Schiff bases and their complexes have also been screened for their antibacterial (Escherichia. coli, S. aureus, S. pyogenes, P. aeruginosa and Salmonella typhi) and antifungal activities (Aspergillus niger, Aspergillus flavus and cladosporium) by MIC method. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties.     

Synthesis and spectroscopic studies of new organotin(IV) complexes with tridentate N- and O-donor Schiff bases

The Schiff bases H₂L¹ and H₂L² have been prepared by the reaction of 2-amino-4-chlorophenol with pyrrole-2-carbaldehyde and 2-hydroxy-1-naphtaldehyde, respectively, and HL³ from reaction of 2-(aminomethyl)pyridine with 2-hydroxy-1-naphtaldehyde. Organotin complexes [SnPh₂(L¹)] (1), [SnPh₂(L²)] (2), [SnMe₂(L²)] (3) and [SnPhCl₂(L³)] (4) were synthesized from reaction of SnPh₂Cl₂ and SnMe₂Cl₂ with these Schiff bases. The synthesized complexes have been investigated by elemental analysis and FT-IR, ¹H NMR and ¹¹⁹Sn NMR spectroscopy. In complexes the Schiff bases are completely deprotonated and coordinated to tin as tridentate ligands via phenolic oxygen, pyrrolic, and imine nitrogens in 1, two phenolic oxygens and imine nitrogen in 2 and 3, and phenolic oxygen, imine and pyridine nitrogens in 4. The coordination number of tin in 1, 2, and 3 is five and in 4 is six.     

Complexes of titanium(IV), vanadium(IV) and tin(IV) with schiff bases derived from 2-(2-aminophenyl)benzimidazole

Summary New titanium(IV), vanadium(IV) and tin(IV) complexes with Schiff bases derived from 2-(2-aminophenyl)benzimidazole with benzaldehyde (L₁) and salicylaldehyde (L₂) have been prepared and have the general formulae MX₄ · 2L (M = Ti, V or Sn; L = L₁ or L₂; X = Cl or Br).All the complexes have been characterized by elemental analyses, magnetic measurements, e.p.r., electronic and i.r. spectral studies. The results show that the Schiff bases act as monodentate ligands. Tentative structures for the complexes are suggested.     

Synthesis,spectral, thermal,solid-state DC electrical conductivity and biological studies of Co(II) complexes with Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and substituted salicylaldehydes

A series of Co(II) complexes have been synthesized with Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and substituted salicylaldehydes. These complexes are insoluble in water but more soluble in DMF and DMSO. The complexes have been characterized by elemental analyses, spectral (IR, UV–Vis, ¹H-NMR, FAB-mass, fluorescence), magnetic, thermal, solid-state DC electrical conductivity and molar conductance data. The molar conductivity values indicate that they are non-electrolytes. The elemental analyses of the complexes suggest a stoichiometry of the type Co · L1–L16 · 2H₂O. The complexes have been considered as semiconductors on the basis of the solid-state DC electrical conductivity data. Fluorescence spectra of one Schiff base and its complex were investigated in various solvents and some of the Schiff bases and their complexes were evaluated for their antimicrobial activities.     

Synthesis,characterization, DNA cleavage,and in-vitro antimicrobial studies of Co(II), Ni(II), and Cu(II) complexes with Schiff bases of coumarin derivatives

A series of Co(II), Ni(II), and Cu(II) complexes ML?·?3H₂O have been synthesized with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazole and 5-formyl-6-hydroxy coumarin. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMF indicate that the complexes are non-electrolytes. In view of analytical, spectral (infrared, UV-Vis, ESR, TG, and FAB-mass), and magnetic studies, it has been concluded that all the metal complexes possess octahedral geometry in which ligand is coordinated to metal through azomethine nitrogen, phenolic oxygen, and sulfur via deprotonation. The Schiff bases and their complexes have been screened for antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella typhi) and antifungal activities (Aspergillus niger, Aspergillus flavus, and Cladosporium) by the minimum inhibitory concentration method. DNA cleavage is studied by agarose gel electrophoresis.     

Magnetic and spectral properties of nickel(II) complexes of ligands containing O,N, and S donor atoms

Summary Several complexes of nickel(II) with Schiff bases derived from 3-substituted-4-amino-5-mercapto-1,2,4-triazoles (H₂L) have been synthesised. The complexes have a stoichiometry NiL · 2H₂O. The bonding of the ligands has been inferred from i.r. spectroscopy. The ligands preserve the thiol in the complexes. Magnetic moments obtained at room temperature and electronic spectra are consistent with octahedral geometry.     

Synthesis,physico-chemical and biological studies on oxovanadium(IV) derivatives of mercaptotriazoles

Summary Complexes of 3-methyl- or 3-ethyl-4-amino-5-thiolato-1,2,4-triazole (LH) and its Schiff base derivatives with oxovanadium(IV), of the types [VOL₂(H₂O)], [VOL₂-(H₂O)] and [VOL(H₂O)₂] (where LH = Schiff bases derived from condensation of LH with benzaldehyde, 2-chlorobenzaldehyde, 4-methoxybenzaldehyde or acetophenone; LH₂ = Schiff bases derived from condensation of LH with salicylaldehyde or o-hydroxyacetophenone) have been prepared and characterized by elemental analyses, electrical conductance, magnetic moments and spectral data. The thermal behaviour of selected complexes was investigated by t.g., d.t.g. and d.s.c. techniques. The antifungal and antiviral activities of the Schiff bases and their corresponding complexes were also investigated.Author to whom all correspondence should be directed.