Template Condensation Research Articles

Structural and in vitro anti-tubercular activity study of (E)-N’-(2,6-dihydroxybenzylidene)nicotinohydrazide and some transition metal complexes

A template condensation of 2,6-dihydroxybenzaldehyde with nicotinic hydrazide at 20 °C yielded a tridendate ligand with the formation of azomethine bond. The structure of the ligand, H3L2 was confirmed with the use of analytical and spectroscopic analysis such as CHN analysis, ESI mass spectrum, FTIR, UV–visible spectrum and NMR techniques. The use of 2D NMR further confirmed the structure of the ligand. Also, five ligand–metal complexes were synthesized using different techniques. The physico-chemical properties of the complexes were determined with the use of melting point determination, conductivity test, micro-analysis, metal content determination (AAS), magnetic susceptibility measurements, FTIR, UV–visible spectra, ESR, TG/DTG and p-Xray diffraction study. The structures of the metal complexes were elucidated based on the analytical and spectroscopic data obtained. However, the anti-tubercular activities of the compounds were evaluated against H37Rv strain of Mycobacterium tuberculosis, in vitro. The results obtained indicated that the metal complexes are more active than isoniazid with MIC = 0.91 µg/mL. V(II) complex was found to be the most active with MIC of 0.62 µg/mL while Cu(II) complex with MIC values of 0.85 µg/mL is the least potent among the metal complexes synthesized. However, the results of the cytotoxicity against vero cells indicated that the metal complexes are more toxic when compared to the standard drug.

In vitro antibacterial and antifungal activities of binuclear transition metal complexes of ONNO Schiff base and 5-methyl-2,6-pyrimidine-dione and their spectroscopic validation

Novel binuclear metal complexes of general formula [M2(PymL)X3] (where: M=Cu(II), Ni(II), Co(II) or Zn(II); X=Cl− or CH3CO2− and PymL=C13H17N4O6) were synthesized by template condensation of Schiff base (L) derived from glycine using 2,3-butanedione, 5-methyl-2,6-pyrimidine-dione and metal chloride/acetate salt in 1:1:2 stoichiometric ratio. Synthesized compounds were characterized by elemental analysis, conductance measurement, magnetic measurement, IR, UV–visible, 1H NMR, 13C NMR, EPR and ESI-MS spectral studies. IR spectral data suggest that Schiff base (L) behaves as tetradentate ligand with two nitrogen and two oxygen donor sites of the azomethine group and carboxylic group, respectively and 5-methyl-2,6-pyrimidine-dione behaves as tridentate ligand with two oxygen atoms of the carbonyl group and one nitrogen atom of pyrimidine ring as binding sites. Physico-chemical data suggest octahedral geometry and non-electrolytic nature of metal complexes. The compounds were evaluated for their antimicrobial property by in vitro antimicrobial screening against bacteria Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Salmonella typhi and fungi Candida albicans and Candida parapsilosis. The results indicate that metal complexes exhibit more activity than free Schiff base (L) against studied bacteria and fungi.

Monomeric, dimeric and polymeric lanthanide(III) complexes of a hexaazamacrocyclic imine derived from 2,6-diformylpyridine and ethylenediamine

A series of mononuclear Ln(III) complexes of a hexaaza Schiff base has been obtained in a template condensation reaction of 2,6-diformylpyridine, ethylenediamine and the appropriate lanthanide nitrate salt. The X-ray crystal structures of the Ce(III), Pr(III), Eu(III) and Y(III) complexes, recrystallized from water or methanol, have been determined. The reaction of the obtained complexes with hydroxide anions results in formation of dinuclear hydroxo-bridged species. In particular, the reaction of sodium hydroxide with a mixture of the starting Eu(III) and Y(III) mononuclear complexes results in the formation of two homodinuclear hydroxo derivatives as well as a mixed Y(III)–Eu(III) hydroxo dimer, as indicated by NMR spectroscopy. The formation of dinuclear hydroxo species was confirmed by the X-ray crystal structure of the [Y2L2(μ-OH)2(H2O)2](NO3)4·4H2O complex. On the other hand, an attempt to crystallize a hydroxo derivative of the La(III) macrocyclic complex resulted in the fixation of atmospheric carbon dioxide and formation of a carbonate derivative. The X-ray crystal structure of this compound reveals a 1-D coordination polymer, where the macrocyclic [LaL]3+ units are linked by bridging carbonate anions.

Tuning the near-IR band energy and redox potentials of magnesium tetra(ferrocenyl)tetraazaporphyrins

Magnesium 2(3),7(8),12(13),17(18)-tetraferrocenyl-5,10,15,20-tetraazaporphyrin (3), and magnesium 2(3),7(8),12(13),17(18)-tetracyano-3(2),8(7),13(12),18(17)-tetraferrocenyl-5,10,15,20-tetraazaporphyrin (4) complexes were prepared using template condensation reaction between magnesium butoxide and (Z)-dicyanovinylferrocene (1) and tricyanovinylferrocene (2), respectively. Redox and unusual optical properties of macrocyclic compounds 3 and 4 were investigated in details using UV-vis, MCD, electro-, and spectroelectrochemical methods as well as DFT and TDDFT calculations. It was shown that the HOMO in both compounds resembles Goutermans' a1u orbital (D4h symmetry), which is different from meso-ferrocenyl containing porphyrins. In both macrocycles 3 and 4 overlapping oxidation waves for ferrocene substituents were observed in electrochemical and spectroelectrochemical experiments. Electrochemically observed oxidation waves are rather broad because of the presence of positional isomers and span only ~300 mV range in DCM/0.05 M TBAF system. Based on the excellent agreement between experimental UV-vis spectra and TDDFT predicted excitation energies, it was suggested that the low-energy NIR and visible regions are predominantly composed by the MLCT transitions with a significant π–π* mixing.

Halogen-bonded tris(2,4-bis(trichloromethyl)-1,3,5-triazapentadienato)-M(iii) [M = Mn, Fe, Co] complexes and their catalytic activity in the peroxidative oxidation of 1-phenylethanol to acetophenone

One-pot template condensation of CCl3CN with ammonia on a metal source [MnCl2·4H2O, FeCl3·6H2O or Co(CH3COO)2·4H2O] in DMSO led to the formation of tris{2,4-bis(trichloromethyl)-1,3,5-triazapentadienato}-M(III) complexes, [M{NHC(CCl3)NC(CCl3)NH}3]·n(CH3)2SO [M = Mn, n = 1 (1); M = Fe, n = 2 (2); M = Co, n = 2 (3)], which were characterized using elemental analysis, and IR, ESI-MS and single-crystal X-ray analysis. The role of inter- and intramolecular non-covalent halogen and hydrogen bonds in the synthesis of 1–3 is discussed. It is shown that the crystal ionic radii of the metal ions [68.5 (Co) 3.155 (2) > 3.133 (1) A]. Compounds 1–3 and the related di(triazapentadienato)-Cu(II) complex [Cu{NHC(CCl3)NC(CCl3)NH}2]·2(CH3)2SO (4) act as catalyst precursors for the additive-free microwave (MW) assisted homogeneous oxidation of 1-phenylethanol with tert-butylhydroperoxide (TBHP), leading to the formation of acetophenone with yields up to 99% and TONs up to 5.0 × 103 after 1 h of low power (10 W) MW irradiation.

Synthesis, characterization and in vitro anticancer activity of 18-membered octaazamacrocyclic complexes of Co(II), Ni(II), Cd(II) and Sn(II)

An effective series of 18 membered octaazamacrocyclic complexes of the type [MLX2], where X=Cl or NO3 have been synthesized by template condensation reaction of oxalyl dihydrazide with dibenzoylmethane and metal salt in 2:2:1 molar ratio. The formation of macrocyclic framework, stereochemistry and their overall geometry have been characterized by various physico-chemical studies viz., elemental analysis, electron spray ionization–mass spectrometry (ESI–MS), I.R, UV–Vis, 1H NMR, 13C NMR spectroscopy, X-ray diffraction (XRD) and TGA/DTA studies. These studies suggest formation of octahedral macrocyclic complexes of Co(II), Ni(II), Cd(II) and Sn(II). The molar conductance values suggest nonelectrolytic nature for all the complexes. Thermogravimatric analysis shows that all the complexes are stable up to 600°C. All these complexes have been tested against different human cancer cell lines i.e. human hepatocellular carcinoma (Hep3B), human cervical carcinoma (HeLa), human breast adenocarcinoma (MCF7) and normal cells (PBMC). The newly synthesized 18-membered octaazamacrocyclic complexes during in vitro anticancer evaluation, displayed moderate to good cytotoxicity on liver (Hep3B), cervical (HeLa) and breast (MCF7) cancer cell lines, respectively. The most effective anticancer cadmium complex (C34H28N10CdO10) was found to be active with IC50 values, 2.44±1.500, 3.55±1.600 and 4.82±1.400 in micro-molar on liver, cervical and breast cancer cell lines, respectively.

Thermal, spectral, magnetic and biologic characterization of new Ni(II), Cu(II) and Zn(II) complexes with a hexaazamacrocyclic ligand bearing ketopyridine moieties

New species of type MLCl2·nH2O (M:Ni, n = 4.5; M:Cu, n = 0 and M:Zn, n = 0; L: (4,5-11,12)-bisphenylen-1,3,6,8,10,13-hexaazacyclotetradecan-bis(pyrid-3-yl)methanone resulted by 1,2-phenylendiamine, nicotinamide and formaldehyde template condensation) were synthesised. The complex features have been assigned from microanalytical, IR, UV–Vis, 1H NMR and EPR spectra as well as magnetic data at room temperature. Simultaneous TG/DTA and TG/DSC/EGA measurements were performed in order to evidence the thermal decomposition pattern and the nature of the gaseous products formed in each step. Processes as water and chloride elimination as well as fragmentation and oxidative degradation of the organic ligand were observed during the thermal decomposition. The final product of decomposition was metal(II) oxide. The obtained complexes exhibited an improved antimicrobial activity in comparison with the ligand, both on planktonic and biofilm embedded cells, as well as a low cytotoxicity. The microbicidal and anti-biofilm activity of the complex (3) against the Gram-negative strains recommend it for the development of new antimicrobial solutions for these emerging multidrug-resistant bacteria causing life-threatening infectious diseases often untreatable with the existing antimicrobial agents. The assay on HEp-2 cells indicates a low cytotoxicity for all complexes. The plethysmometry assays indicate an anti-inflammatory activity for Cu(II) complex.

Template Synthesis, Structural Characterization and Antibacterial Activity of an Unsymmetrical Tridentate Schiff Base Nickel(II) Complex

Nickel(II) complex of [NiL2](ClO4)2, where L is an unsymmetrical tridentate ligand of 2-(2-aminoethyl)imino-3-butanone oximehas been synthesized by a template condensation reaction. The complex was characterized on the basis of microanalytical, spectroscopic, and other physicochemical properties. X-ray diffraction study of the complex reveals nickel(II) center in a distorted octahedral environment through two amine nitrogen donors, two imine donors,and two nitrogen atoms of the oxime moieties of the ligand. The antibacterial activity of the complex has been tested against Gram(+) and Gram(-) bacteria. The results of the antibacterial screening indicated that the complex is effective against bacterial growth retardation activity to some extent and its effectiveness is higher for Gram(+) bacteria.

Thermal behaviour of some novel antimicrobials based on complexes with a Schiff base bearing 1,2,4-triazole pharmacophore

A series of complexes of type [ML(CH3COO)(OH2)2] (M: Co, Ni; HL: 2-[(E)-1H-1,2,4-triazol-3-ylimino)methyl]phenol)) and [M2L2(CH3COO)2(OH2)n] (M: Cu, n = 2; M: Zn, n = 0) were synthesised by template condensation. The compounds were characterised with microanalytical, ESI–MS, IR, electronic, EPR spectra and magnetic data at room temperature. Based on the IR and ESI–MS spectra, a dinuclear structure with the acetate as bridge was proposed for Cu(II) and Zn(II) complexes. The dinuclear structure of Cu(II) complex is also consistent with both magnetic behaviour and EPR spectrum. The thermal analyses have evidenced processes as water elimination, acetate decomposition, as well as oxidative degradation of the Schiff base. The final decomposition product was the most stable metal oxide as indicated by powder X-ray diffraction. The cobalt and copper compounds exhibited a broad spectrum of antibacterial activity towards both planktonic and biofilm-embedded cells. The complexes exhibit a low cytotoxicity except for Cu(II) species that induces the early apoptosis for the HEp 2 cells.

Molecular modelling, spectroscopic characterization and biological studies of tetraazamacrocyclic metal complexes

Macrocyclic complexes of the type [MLX]X2; where L is (C30H28N4), a macrocyclic ligand, M=Cr(III) and Fe(III) and X=Cl−, CH3COO− or NO3−, have been synthesized by template condensation reaction of 1,8-diaminonaphthalene and acetylacetone in the presence of trivalent metal salts in a methanolic medium. The complexes have been formulated as [MLX]X2 due to 1:2 electrolytic nature of these complexes. The complexes have been characterized with the help of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, infrared, far infrared, Mass spectral studies and molecular modelling. Molecular weight of these complexes indicates their monomeric nature. On the basis of all these studies, a five coordinated square pyramidal geometry has been proposed for all these complexes. These metal complexes have also been screened for their in vitro antimicrobial activities.

New bidimensional honeycomb CoII–FeIII and brick wall FeII–CoIII cyanido-bridged coordination polymers: Synthesis, crystal structures and magnetic properties

New bidimensional cyanido-bridged heterometallic coordination polymers, [{Co(L1)}3{Fe(CN)6}2]·6CH3OH·6H2O (1) and [{Fe(L2)}3{Co(CN)6}2]·2CH3OH·13H2O (2), have been assembled following a building-block approach (L1 and L2 are macrocyclic ligands obtained by the template condensation between 2,6-diacetylpyridine and 3,4-dioxaoctane-1,8-diamine, and triethylenetetramine, respectively). The crystal structure of 1 consists of honeycomb layers, each [FeIII(CN)6]3− unit connecting three [Co(L1)]2+ nodes through three facial cyanido groups. On the other hand, the self-assembly process between [CoIII(CN)6]3− and [Fe(L2)]2+ ions affords 2-D layers with a brick wall topology. Each [CoIII(CN)6]3− metalloligand is surrounded by three [Fe(L2)]2+ units, which adopt a meridional configuration around the cobalt metalloligand for compound 2. The magnetic properties of the two compounds have been investigated. Compound 1 shows a ferromagnetic order below 3K. The magnetic properties of 2 are characteristic of non-interacting high spin FeII ions, which exhibit a moderate uniaxial magnetic anisotropy (D/kB=−5.5K).

Spectroscopic and antibacterial studies of new octaazamacrocyclic complexes derived from carbohydrazide and isatin

A novel series of the macrocyclic complexes of the type: [M(C18H14N10O2)X2], where M=Co(II), Ni(II), Cu(II) and Zn(II); X=Cl−, NO3− and CH3COO−, has been synthesized by template condensation of carbohydrazide and isatin in methanolic medium. The complexes were characterized by various physico-chemical techniques, such as elemental analyses, molar conductance measurements, magnetic measurements, and electronic, NMR, IR and EPR spectral studies. The low value of molar conductance indicates them to be non-electrolytes. Based on various studies, a distorted octahedral geometry was proposed for all the metal complexes. Metal complexes were tested for their in vitro antibacterial activities against some pathogenic bacterial strains and compared with standard antibiotic, Ciprofloxacin. Some of the tested complexes was found effective against Gram-positive bacterial strains.

Azamacrocycle Complexes: Synthesis and Xanthine Oxidase and Antioxidant Activity

Aims: Gout is caused by high uric acid in the blood that leads to excess uric acid crystallizing in the joints causing swelling and pain. Uric acid is produced from the breakdown of the purine which is released when cells die or introduced from the food we eat. The enzyme that helps in breakdown of purine to uric acid is xanthine oxidase (XO). Since XO makes the conversion of purine into uric acid happen, preventing its activity results to slow down of uric acid production. Such is the role of xanthine oxidase inhibitors (XOI). In this context we aimed to synthesize new complex which can be potent towards XOI and antioxidant properties.Study Design: Based on the literature we have designed azamacrocyclic complexes for advanced biological applications.Place and Duration of Study: Department of Chemistry, Research Laboratory, Yuvaraj’s College, University of Mysore, Mysore for synthesis and for biological activities Mahajana Life Science Research Laboratory, Department of Biotechnology, Microbiology and Biochemistry. June 2012-may 2013.Methodology: The macrocyclic metal complexes were synthesized by the template condensation of diamine and formaldehyde in MeOH. After stirring for 10 min a solution of 1, 4-diaminobutane, metallic salt and 2, 4-pentanedione in MeOH was added and the resulting mixture was refluxed.Results: Macrocylic metal complexes containing phenylene bridges have been synthesized and subjected to biological activities. Among the four synthesized complexes (3a-3d), 3d exhibited 83.2% of XO inhibition and also showed potent antioxidant activity. The same was also evident from structure activity relationship with atomic contact energy values of -285.78 compared to allopurinol with -200.02.Conclusion: From the present study, we infer that, aza macrocyclic metal complexes could lead to the development of newer therapeutics for gout and other inflammatory diseases which are caused by oxidative stress.

ChemInform Abstract: Zinc(II)‐1,3,5‐triazapentadienate Complex as Effective Catalyst in Henry Reaction

AbstractReview: 35 refs.

Synthesis and Characterization of Template Cr(III),Fe(III), Mn(II), Cd(II) and V(IV), Complexes Derived from 2,6- Diaminopyridine and 1,4-Dihydro-Quinoxalin-2,3-dione.

A new series of tetradentate N2O2 acyclic complexes of type (M(L)X2)Xn where M = Mn(II), Cd, Cr(III) and Fe(III); L is tetradentate acyclic Schiff base formed via condensation reaction, and X = Cl-, n=1 for M(III), have been prepared on the basis of condensation of 2,6-diaminopyridine and 1,4-dihydro-quinoxalin-2, 3-dione by template method. The complexes are formulated as: (M(L)Cl)Cl where M=Cr, Fe(III),(MLCl2),MII=Mn, Cd(II) and (VOL)SO4 on the basis of elemental analyses,molar conductance and other spectral data. The organic moiety formed up on template condensation behaves as tetradentate N2O2 system through the two azomethine nitrogen atoms of -C=N- and the participation of O atoms of -C=O in 2- position of pyrazine ring. However, the pyridine nitrogen atom does not take part in coordination as confirmed by FTIR,UV-Visible and H NMR spectroscopy data. The newly template metal complexes have characterized with the help of various spectral techniques H NMR,13C NMR, F.T.I.R, elemental analyses, electronic spectra, molar conductivity measurements and magnetic susceptibilities. The octahedral geometry has been proposed for Cr(III),Fe(III), Mn (II) and Cd(II) while vanadyl complex was square pyramid configuration respectively. Keywords: Template complex, Quinoxaline-3, 2-dione, Schiff bases.

SYNTHESIS AND CHARACTERIZATION OF OCTAAZATRICYCLOTETRACOSANE (OCTC) MACROCYCLIC COMPLEXES OF NI (II), CU (II) TRANSITION METAL IONS DERIVED FROM 1, 3-DIAMINOPROPANE CONTAINING AZA LIGANDS

This paper deals with the synthesis and characteriz ation of macrocyclic ligand and its complex compoun d. Template condensation of chlorocarbons such as 1,1,2,2-tetrachloroethane wit h 1,3-diaminopropane in presence of nickel (II) or copper (II) yielded the corresponding metal complexes such as 3,7,10,14,15, 19,20,24- octaazatricyclotetracosane (OCTC) . The macrocyclic ligands and their complexes have been characterized by elementa l analysis, molecular weight determination, conduct ance, IR and NMR spectral studies. The magnetic moments, along with electroni c spectral data suggested hexa coordinated state fo r Nickel, its geometry is outer orbit octa hedral and tetra coordinated state for c opper, its geometry is square planner .Conductivity data suggests that they behave as electrolytes. The formulation of the complexes h as been established on the basis of chemical compos ition.

Synthesis, electronic spectroscopy, electrochemistry and catalytic activity of a new Co (II) complex of 1,4,8,11-tetraaza[14]annulene derivative

A new Co (II) complex of 6,13-disubstituted 1,4,8,11-tetraaza[14]annulene derivative has been synthesized by template condensation reaction of 2-(1-quinolinium-1-yl) trimethinium salt (B) with 1,2-diaminopyridine in the presence of Co (II) acetate in DMF. The electrochemical behavior of the metal complex showed a CoII/CoI redox couple at about −0.99V vs. Ag/Ag+ in DMF solvent. Axial ligation of N-donor ligands such as pyridine and imidazole was found to shift the reduction potential of CoII/CoI to more negative potential. The binding of N-donor axial ligands to the metal complex was monitored by measuring changes at about 458nm (maximun absorption of the metal complex) and shifts in the CoII/CoI redox couple potential upon addition of various concentrations of the N-donor axial ligand. Results showed that the number of axial ligand molecules bound to the metal complex is ≈1 and the oxidized state of cobalt (CoII) is more stabilized than the reduced state (CoI) in the presence of the axial ligand. The metal complex also showed catalytic activity toward hydrogen peroxide decomposition in the presence of the N-donor axial ligand.

Coordination compounds of copper(II) with substituted 3-{[(2-hydroxyphenyl)methylidene]amino}propane-1,2-diols

3-{[(2-Hydroxyphenyl)methylidene]amino}propane-1,2-diol, its 5-chloro-,5-bromo-, 5-nitro-, 3-methoxy derivatives, and 3-{[(2-hydroxynaphthyl-1)methylidene]amino}propane-1,2-diol react with hydrates of copper(II) chloride, bromide and nitrate in ethanol to form coordination compounds Cu(L)X·nH2O. Template condensation reaction between 3-aminopropane-1,2-diol and 2,3-, 2,4- or 2,5-dihydroxybenzaldehyde in the presence of copper(II) nitrate trihydrate results in similar compounds Cu(L)NO3·nH2O. Structure of some of the condensation products was identified by X-ray analysis. Thermolysis of the substances obtained occurs through the dehydration step (70–90°C) and complete thermal decomposition (290–560°C).

Trivalent transition metal complexes derived from carbohydrazide and dimedone

A new series of the complexes has been prepared by template condensation reaction of dimedone and carbohydrazide in the methanolic medium forming the complexes of the type [M(TML)X]X2; where TML is a tetradentate macrocyclic ligand; M=Cr(III), Fe(III); X=Cl−, NO3-, CH3COO−. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, infrared, far infrared spectral and structural studies. Molar conductance values indicate them to be 1:2 electrolytes. Electronic spectra along with magnetic moments suggest the five coordinate square pyramidal geometry for these complexes. The complexes have also been tested for their in vitro antibacterial activity by agar well diffusion method and macro dilution tube method. Some of the complexes showed good antibacterial activity.

Synthesis, Characterization, Electrochemical and Antimicrobial Activity of Macrocyclic Binuclear Cu(II), Ni(II) and VO(II) Schiff Base Complexe

A template condensation of 3,3'- diaminobenzidine with benzil and dimethyl ortho- phenylenediamine in the presence of Cu(II), Ni(II) and VO(II) resulted in the formation of tetradentate macrocyclic Schiff base binuclear complexes of the type (M2 L.X) and (M2 L). X2 (where, X= 2ClO4 - , CH3COO - and 2SO4 - ). Structural characterization of the complexes were achieved by several physicochemical methods, namely elemental analysis, electronic spectra, infrared, EPR, cyclic voltammetry, molar conductivity and magnetic susceptibility measurements. A square planar binuclear structure was proposed for the perchlorate anions in Cu(II) and Ni(II) complexes. Whereas the square pyramidal environment around the VO(II) center. The Schiff base complexes were investigated for antibacterial and antifungal properties of gram-positive bacteria (staphylococcus auerus), gram- negative bacteria (pseudomonas fluorescens) and fungi (Aspergillus fumigatus) were used in this study to assess their antimicrobial properties. The results showed that this skeletal framework exhibit marked potency as antimicrobial agents.