Main Group Chemistry

Zn(II) complexes have been synthesized by reacting zinc acetate with Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-oxadiazole and appropriate aldehyde (benzaldehyde/2-hydroxyacetophenone) and indoline-2,3-dione. All these complexes are soluble in DMF and DMSO. Low molar conductance values indicate that they are non electrolytes. Elemental analysis suggests that the complexes have 1 : 2 stoichiometry of the type [ZnL'₂(OOCCH₃)₂.2H₂O], [ZnL₂.2H₂O] (L' = Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-oxadiazole and benzaldehyde; LH = Schiff bases derived from 2-hydrazino-5-[substituted phenyl]-1,3,4-oxadiazole and 2-hydroxyacetophenone/indoline-2,3-dione) and they were characterized by IR, ¹H NMR and ¹³C NMR. All these Schiff bases and their complexes have also been screened for their antibacterial (Bacillus subtilis, Pseudomonas aeruginosa, Salmonella typhi and Streptococcus pyogenes) antifungal activities (Colletrotrichum falcatum, Aspergillus niger, Fusarium oxysporium and Carvularia pallescence) by reported method.

Ti(IV), VO(II), Ni(II), Co(II), Mn(II), Cu(II), Zn(II), Cd(II), Sn(II), ZrO(II), UO₂(II) Fe(III), Ru(III), Ho(III) and Yb(III) complexes of 2-(p-toluidino)-N′-(2-hydroxbenzylidene) acetohydrazide have been prepared and characterized on the basis of various spectroscopic techniques like electronic, EPR, FT-IR and ¹H NMR studies, elemental analysis, magnetic properties and thermo-gravimetric analysis, and also by the aid of molar conductivity measurements. It is found that the Schiff base behaves as a monobasic tridentate, monobasic bidentate or dibasic tridentate ligand bonding to the metal ions via the oxygen atom of carbonyl oxygen atom in the enolic or ketonic form, azomethine nitrogen atom and/or oxygen atom of deprotonated phenolic hydroxyl group with 1 : 1 or 1 : 2 metal to ligand stoichiometry. Octahedral geometries have been assigned for Ni(II), Co(II), Mn(II), Fe(III) and Ru(III) complexes, tetragonally distorted octahedral geometry has been suggested for Cu(II) complexes, while square pyramidal geometry has been proposed for VO(II) complexes. The compounds were subjected to antimicrobial activity screening using Well diffusion method. Complexes (2), (8), (9), (10), (11), (13), (15) and (16) exhibit inhibitory effect towards fungus (Aspergillus niger) more than the parent ligand. However complexes (6), (2), (11), (12), (9), (16), (13), (5), (18), (15), (19), (8) and (7) are noticeable for antibacterial activity at the same concentration.

The cobalt(II) complex [Co(tta)₂(H₂O)₂] (3) was prepared by the reaction of [Co(OAc)₂·4H₂O] (2) (OAc = O₂CMe) with two equivalents of 1-(2-Thenoyl)-3,3,3-trifluoroacetone (H-tta, 1). Replacement of the aqua ligands in 3 was possible by addition of methanol giving [Co(tta)₂(HOMe)₂] (4). On gentle heating metal-organic 3 to 134–165°C, complex [Co­(tta)₂] (5) was formed. The structure of 4 in the solid state was determined by single X-ray structure analysis. Crystal data for C₁₈H₁₈CoF₆O₆S₂ are: a = 10.3502(7), b = 10.3589(8), c = 11.7177(10) Å, α = 97.376(7), β = 114.807(7), γ = 97.950(6)°, space group P-1, Z = 2, and d_calc = 1.705 mg/m³. Complex 4 possesses a distorted octahedral coordination sphere at cobalt, whereby the coordination sites are occupied by two chelated tta ligands and two cis-coordinated methanol molecules. Formation of intermolecular MeO–H${\cdots}$O_diketonate hydrogen bridges resulted in the setup of a 1D chain. Through additional π–π interactions between thiophene rings of individual chains a band structure along the crystallographic b axes is generated.

A new N-alkyl long-chain alkyl imine ligand (N-dodecyl-N1-dacanimine) has been synthesized by the reaction of dodecylamine (laurylamine) with decanal in molar 1 : 1 ratio and its Cu(I), Cu(II), Ni(II) and Co(II) complexes have been prepared under solvent-free conditions. The newly synthesized compounds have been verified by FTIR, UV-vis. and mass spectra. All of the compounds were tested for antimicrobial activity against Staphylococcus aureus ATCC 6538, meticillin resistant Staphylococcus aureus (MRSA) ATCC 33591, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 8739, Klebsiella pneumoniae ATCC 4352, Pseudomonas aeruginosa ATCC 1539, Proteus mirabilis ATCC 14153 and the yeast, Candida albicans ATCC 10231. Among the compounds, the ligand was found the most active compound against all strains. The Cu(II)complex exhibited very strong antibacterial activity against bacteria except for Pseudomonas aeruginosa ATCC 1539, Proteus mirabilis ATCC 14153. Also, all compounds showed very strong antifungal effects against C. albicans ATCC 10231.

[In(Me₂phen)Cl₃(DMSO)]·DMSO complex (1) (Me₂phen is 5,6-dimethyl-1,10-phenanthroline and DMSO is dimethyl sulfoxide) and [In(Ph₂phen)Cl₃(CH₃CN)] complex (2) (Ph₂phen is 4,7-diphenyl-1,10-phenanthroline) were prepared from the reaction of 5,6-dimethyl-1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline with InCl₃·4H₂O in methanol, respectively. Both complexes were characterized by IR, UV-Vis, NMR and luminescence spectroscopy and their structures were studied by the single-crystal diffraction method. In the crystal structure of complex 1, there are intra- and intermolecular C-H${\cdots}$Cl and C-H${\cdots}$O hydrogen bonds and π−π contacts. In complex 2, there are intermolecular C-H${\ldots}$Cl hydrogen bonds. The luminescence emission spectra of Me₂phen and 1, and Ph₂phen and 2, were obtained in DMSO and CH₃CN at room temperature, respectively. The shapes of the emission spectra for Me₂phen, Ph₂phen, 1 and 2 are similar but the luminescent emission of complexes of 1 and 2 are weaker than those of free Me₂phen and Ph₂phen ligands. There are red shifts of the emission energies of the Ph₂phen ligand after coordination to In(III) for complex 2.

The tris(dimethyldithioarsinato) complexes M(S₂AsMe₂)₃ (M = Al, Ga, In and Tl) have been prepared from NaS₂AsMe₂·2H₂O as anhydrous powders. The Al and Ga, but not the In and Tl, complexes add water molecules seen in the IR(KBr) spectra. The Al and Ga coordinate, while the In and Tl complexes attract and polarize water in CDCl₃ resulting in more than one signal for H₂O in the ¹H NMR spectra. All four complexes are desulfurized by Ph₃P but the expected M(SAsMe₂)₃ are unstable and decompose to Me₂As-S-AsMe₂ and other products.