A new Mannich base and its transition metal (II) complexes — Synthesis, structural characterization and electrochemical study

Synthesis, Characterisation, and Biological Evaluation of Zn(II) Complex with Tridentate (NNO Donor) Schiff Base Ligand

The present paper deals with the synthesis and characterization of metal complex of tridentate Schiff base ligand derived from the inserted condensation of 2-aminobenzimidazole (1H-benzimidazol-2-amine) with salicylaldehyde (2-hydroxybenzaldehyde) in a 1 : 1 molar ratio. Using this tridentate ligand, complex of Zn(II) with general formula ML has been synthesized. The synthesized complex was characterized by several techniques using molar conductance, elemental analysis, FT-IR, and mass and 1HNMR spectroscopy. The elemental analysis data suggest the stoichiometry to be 1 : 1 [M : L]. The complex is nonelectrolytic in nature as suggested by molar conductance measurements. Infrared spectral data indicate the coordination between the ligand and the central metal ion through deprotonated phenolic oxygen, imidazole nitrogen of benzimidazole ring, and azomethine nitrogen atom. Spectral studies suggest tetrahedral geometry for the complex. The pure compound, synthesized ligand, and metal complex were screened for their antimicrobial activity.

Mannich bases: an important pharmacophore in present scenario

Mannich bases are the end products of Mannich reaction and are known as beta-amino ketone carrying compounds. Mannich reaction is a carbon-carbon bond forming nucleophilic addition reaction and is a key step in synthesis of a wide variety of natural products, pharmaceuticals, and so forth. Mannich reaction is important for the construction of nitrogen containing compounds. There is a number of aminoalkyl chain bearing Mannich bases like fluoxetine, atropine, ethacrynic acid, trihexyphenidyl, and so forth with high curative value. The literature studies enlighten the fact that Mannich bases are very reactive and recognized to possess potent diverse activities like anti-inflammatory, anticancer, antifilarial, antibacterial, antifungal, anticonvulsant, anthelmintic, antitubercular, analgesic, anti-HIV, antimalarial, antipsychotic, antiviral activities and so forth. The biological activity of Mannich bases is mainly attributed to α, β-unsaturated ketone which can be generated by deamination of hydrogen atom of the amine group.

Synthesis and Cytotoxicity Evaluation of Some Novel 1-(3-Chlorophenyl)piperazin-2-one Derivatives Bearing Imidazole Bioisosteres

A series of substituted 3-chlorophenylpiperazinone derivatives were synthesised using L-778123 (an imidazole-containing FTase inhibitor) as a model by bioisosteric replacement of the imidazole ring. The final compounds were evaluated against two human cancer cell lines including A549 (lung cancer) and HT-29 (colon cancer) by MTT assay. The results showed that substitution of imidazole ring with 1-amidinourea, semicarbazide, and thiobiuret led to improvement of cytotoxic activity against both cell lines.

Coordination modes, spectral, thermal and biological evaluation of hetero-metal copper containing 2-thiouracil complexes

Mononuclear copper complex [CuL(NH(3))(4)]Cl(2)·0.5H(2)O and three new hetero-metallic complexes: [Cu(2)Ni(L)(2)(NH(3))(2)Cl(2)·6H(2)O] 2H(2)O(,) [Cu(3)Co(L)(4)·8H2O]Cl·4(·)5H(2)O, and [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O where L is 2-thiouracil, were prepared and characterized by elemental analyses, molar conductance, room-temperature magnetic susceptibility, spectral (IR, UV-Vis and ESR) studies and thermal analyses techniques (TG, DTG and DTA). The molar conductance data revealed that [CuL(NH(3))(4)]Cl(2)·0.5H(2)O and [Cu(3)Co(L)(4)·8H2O]Cl·4.5H(2)O are electrolytes, while, [Cu(2)Ni(L)(2)(NH(3))(2)Cl(2·)6H(2)O]·2H(2)O and [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O are non-electrolytes. IR spectra showed, that 2-thiouracil ligand behaves as a bidentate or tetradentate ligand. The geometry around the metal atoms is octahedral in all the prepared complexes except in [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O complex where square planar environment around Co(II), Ni(II) and Cu(II) were suggested. Thermal decomposition study of the prepared complexes was monitored by TG, DTG and DTA analyses under N(2) atmosphere. The decomposition course and steps were analyzed. The order of chemical reactions (n) was calculated via the peak symmetry method and the activation parameters of the non- isothermal decomposition were computed from the thermal decomposition data. The negative values of ΔS(∗) deduced the ordered structures of the prepared complexes compared to their starting reactants. The antimicrobial activity of the prepared complexes were screened in vitro against a Gram positive, a Gram negative bacteria, a filamentous fungi and a yeast. The antimicrobial screening data showed that the studied compounds exhibited a good level of activity against Escherichia coli, Staphylococcus aureus and Candida albicans but have no efficacy against Aspergillus flavus. It was observed that [Cu(4)Co(2)Ni(L)(3)(OH)(4)(NH(3))Cl(4)·3H(2)O]4H(2)O complex showed the most intensive activity against the tested microorganisms. Trials to prepare single crystals from complexes were failed.

Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, (1)H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.

3-{1-[4-(2-Methyl-prop-yl)phen-yl]eth-yl}-1-(morpholinometh-yl)-4-(4-nitro-benzyl-ideneamino)-1H-1,2,4-triazole-5(4H)-thione

The title ibuprofen-containing Mannich derivative, C(26)H(32)N(6)O(3)S, crystallizes with two independent mol-ecules in the asymmetric unit. The morpholine ring in each mol-ecule adopts a chair conformation. The 1,2,4-triazole ring forms dihedral angles of 2.13 (10) and 75.52 (10)° with the two substituted benzene rings in one mol-ecule, with corresponding values of 19.36 (11)° and 89.03 (10)° in the other. The nitro groups are twisted from the attached benzene ring in each mol-ecule. In the crystal packing, mol-ecules are linked into supra-molecular chains via weak C-H⋯O, C-H⋯N and C-H⋯S inter-actions, and C-H⋯π and N-O⋯π links also occur.

4-(4-Bromobenzylideneamino)-3-{1-[4-(2-methylpropyl)phenyl]ethyl}-1-(morpholinomethyl)-1H-1,2,4-triazole-5(4H)-thione

There are two mol­ecules (A and B) in the asymmetric unit of the title compound, C₂₆H₃₂BrN₅OS, with almost identical geometry. The morpholine ring adopts the usual chair conformation in both mol­ecules. The triazole ring forms dihedral angles of 4.84 (6) and 74.19 (6)°, respectively, with the bromo­phenyl and isobutylbenzene rings in mol­ecule A, and angles of 16.68 (7) and 87.29 (6)°, respectively, in mol­ecule B. Intra­molecular C—H⋯S hydrogen bonds generate S(5) and S(6) ring motifs in both independent mol­ecules. The crystal structure is stabilized by C—H⋯N, C—H⋯Br and C—H⋯O hydrogen-bonding inter­actions, together with C—H⋯π inter­actions.