Electronic Spectral Studies Research Articles

Synthesis and Structure of a Ternary Copper(II) Complex with Mixed Ligands of Diethylenetriamine and Picrate: DNA/Protein-Binding Property and In Vitro Anticancer Activity Studies.

Based on the importance of the design and synthesis of transition metal complexes with noncovalent DNA/protein-binding abilities in the field of metallo pharmaceuticals, a new mononuclear ternary copper(II) complex with mixed ligands of diethylenetriamine (dien) and picrate anion (pic), identified as [Cu(dien)(pic)](pic), was synthesized and characterized by elemental analysis, molar conductivity measurement, infrared spectrum, electronic spectral studies, and single-crystal X-ray diffractometry. The structure analysis reveals that the copper(II) complex crystallizes in the monoclinic space group P21 /c, and the copper(II) ion has a distorted square pyramidal coordination geometry. A two-dimensional supramolecular structure is formed through hydrogen bonds. The DNA/bovine serum albumin (BSA)-binding properties of the complex are explored, indicating that the complex can interact with herring sperm DNA via intercalation mode and bind to BSA responsible for quenching of tryptophan fluorescence by static quenching mechanism. The in vitro anticancer activity shows that the copper(II) complex is active against the selected tumor cell lines.

Tridentate hydrazone metal complexes derived from cephalexin and 2-hydrazinopyridine: Synthesis, characterization and antibacterial activity

Metal(II) coordination compounds of a tridentate hydrazone ligand (HL) derived from the condensation of cephalexin antibiotic with 2-hydrazinopyridine were synthesized. The hydrazone ligand and mononuclear [ML(OAc)(H2O)] (M(II)=Mn, Co, Ni, Cu, Zn, Ag) complexes were characterized by several techniques, including elemental and thermal analysis, molar conductance and magnetic susceptibility measurements, electronic, FT-IR, EPR and 1H NMR spectral studies. The cephalexin 2-pyridinylhydrazone ligand HL behaves as a monoanionic tridentate NNO chelating agent. The biological applications of complexes have been studied on three bacteria strains (Escherichia coli, Acinetobacter baumannii and Enterococcus faecalis) by agar diffusion disc method.

Synthesis and crystal structure of new dicopper(II) complexes with N,N′-bis-(dipropylenetriamine)oxamide as bridging ligand: Effects of the counterions on DNA/protein-binding property and in vitro antitumor activity

Two new dicopper(II) complexes bridged by N,N′-bis(dipropylenetriamine)oxamide (H2oxdipn), namely, [Cu2(oxdipn)](pic)2(1) and [Cu2(oxdipn)(ClO4)2] (2), where pic represents picrate ion, have been synthesized and characterized by elemental analyses, molar conductance measurements, IR and electronic spectral studies, and X-ray single crystal diffraction. In both dicopper(II) complexes, the two copper(II) ions are bridged by trans-oxdipn ligand with the Cu⋯Cu separations of 5.2536(15) and 5.231(2)Å, respectively. The copper(II) ion in complex 1 has a square-planar coordination geometry, while that in 2, a square-pyramidal. Linked with classical hydrogen bonds, the molecules of complex 1 consist of a one-dimensional chain, while complex 2 molecules result in a two-dimensional structure. Numerous hydrogen bonds link complex 1 or 2 into a 2-D infinite network. In vitro cytotoxicity experiment shows that the two dicopper(II) complexes exhibit cytotoxic effects against the selected tumor cell lines. The reactivity towards herring sperm DNA (HS-DNA) and bovine serum albumin (BSA) reveals that the two dicopper(II) complexes can interact with the DNA in the mode of intercalation, and effectively quench the intrinsic fluorescence of BSA via a static mechanism. The influence of different counterions in this kind of dicopper(II) complexes on DNA/BSA-binding properties, and the in vitro cytotoxic activities was investigated.

Studies on metal complexes of 1-((8-hydroxyquinolin-5-yl)methyl)-3-(thiazol-2-ylimino)indolin-2-one

Novel ligand 1-((8-hydroxyquinolin-5-yl)methyl)-3-(thiazol-2-ylimino)indolin-2-one was synthesized by condensation of 5-(chloromethyl)-1,8a-dihydroquinolin-8-ol with 3-(thiazol-2-ylimino)indolin-2-one. Metal complexes of this ligand were prepared using various transition metal ion salts, viz., Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II). All synthesized compounds were characterized by various spectroscopic techniques. Thermogravimetric analysis of metal complexes was also carried out. Geometry of the metal complexes was carried out by electronic spectral analysis and magnetic measurement studies. The ligand and metal complexes were screened for their antibacterial activities against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Proteus vulgaris, and Pseudomonas aeruginosa. The metal complexes are found more potent bactericides than the ligand. The interaction of ligand and its complexes with plasmid (pUC 19) DNA and calf thymus DNA was investigated by gel electrophoresis measurements. The superoxide dismutase mimetic activity of the ligand and its metal complexes has also been assessed for their ability to inhibit the reduction of nitrobluetetrazolium chloride.

Preparation, Characterization and Biological Studies of Adducts of Bis(O-isopropyldithiocarbonato)oxovanadium(IV) with Nitrogen Donor Ligands

A series of adducts of bis(O-isopropyldithiocarbonato)oxovanadium(IV) with substituted pyridines have been synthesized by treating bis(O-isopropyldithiocarbonato)oxovanadium(IV) with substituted pyridines in acetone in equimolar ratios. Analytical results show that the adducts have 1:1 stoichiometry with general formula VO(O-isopropyldithiocarbonato)2L where L = 2 and 3-bromopyridine; 4-acetylpyridine; 3-hydroxypyridine; 2-methoxypyridine; 2-amino-3-methylpyridine; 2-amino-4-methylpyridine; 2-amino-6-methylpyridine). The addition complexes have been characterized by elemental analysis, conductivity measurements, magnetic susceptibility measurements, infrared and electronic spectral studies. These studies suggest a distorted octahedral structure and paramagnetic nature of the adducts. Antifungal activity of some adducts have been carried out against the fungal strain Sclerotium rolfsii. Xanthate have recently been shown to inhibit the replication of both DNA and RNA viruses in vitro. It was found that certain xanthate derivatives exhibit beneficial antimicrobial and antiviral effects 7 . Here we report synthesis and investigation of the 1:1 adducts of some adducts of oxovanadium(IV)xanthates with substituted pyridines such as 2 and 3-bromopyridine; 4-acetylpyridine; 3-hydroxypyridine; 2-methoxypyridine; 2-amino-3- methylpyridine; 2-amino-4-methylpyridine and 2-amino-6-methylpyridine.

Synthesis, Characterization, Antioxidant, and Antibacterial Studies of Some Metal(II) Complexes of Tetradentate Schiff Base Ligand: (4E)-4-[(2-{(E)-[1-(2,4-Dihydroxyphenyl)ethylidene]amino}ethyl)imino]pentan-2-one.

Co(II), Ni(II), Cu(II), and Zn(II) complexes of (4E)-4-[(2-{(E)-[1-(2,4-dihydroxyphenyl)ethylidene]amino}ethyl)imino]pentan-2-one have been synthesized and characterized by elemental analyses, molar conductance, electronic and IR spectral studies, and XRD. FTIR confirmed the ligand coordinates the metal ion to form mononuclear complex via the oxygen and nitrogen atoms of the phenolic group and azomethine group, respectively. Tetrahedral geometry is proposed for Co(II) complex and square-planar geometry for Ni(II) and Cu(II) complexes. The antibacterial studies of the compounds were determined and they show that the metal complexes are more active than the free ligands. The antioxidant activity by DPPH and ABTS method was examined and it shows Cu(II); IC50 = 2.31 ± 1.54 µM for DPPH and Co(II); IC50 = 1.83 ± 1.08 µM for ABTS were the most active.

Synthesis and Characterization of Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) Complexes of Schiff Base Derived from Isonicotinoyl Hydrazone.

2-hydroxy-5-chloro-3-nitroacetophenone isonicotinoyl hydrazone as a Schiff base ligand and its complexes with Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) metal ions have been synthesized. The ligands as well as their metal complexes were well characterized using various physicochemical techniques such as elemental analyses, molar conductance measurements, magnetic measurements, thermal analysis, electronic and IR spectral studies. On the basis of these studies, square pyramidal stereochemistry for Mn(III) and VO(IV) complexes while octahedral stereochemistry for all the other complexes have been suggested. The complexes were found to be stable up to 60-70° and thermal decomposition of the complexes ended with respective metal oxide as a final product. The thermal data have been analyzed for kinetic parameters using Broido and Horowitz-Metzger methods. The synthesized Schiff base ligand and its complexes were also tested for their antimicrobial activity using various microorganisms.

Synthesis and characterization of manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) mixed ligand complexes with [(1-phenyl-3- methyl-5- hydroxopyrazol-4-yl) methylimino] 2′, 3′ dimethylaniline and 2- hydroxy-1-naphthaldehyde

Mixed ligand complexes of the type [MLL ' ] where M = Mn (II), Co (II), Ni (II), Cu (II), Zn (II) HL = [(1-phenyl-3methyl-5-hydroxopyrazol-4-yl)phenylimino]2,3-dimethylaniline; (HPMPZP)dma. HL ' = 2-hydroxy-1-naphaldehyde; (HNA), have been synthesized and characterized on the basis of elemental analysis, conductivity measurements, magnetic, electronic and infra red spectral studies. The complexes confirm to 1:1:1 stoichiometry and are non electrolytes. The schiff base HL act as a monovalent bidentate ligand co-ordinating through azomethine nitrogen and phenolic oxygen. On the basis of electronic spectra, IR spectra and magnetic moment measurements; six coordinated octahedral structures have been proposed for the complexes. Thermal studies revealed the presence of two co-ordinated water molecules. The shiff base and mixed ligand complexes have been tested for their antibacterial activity against the Escherichia coli, Bacillus substilis, staphylococcus aureus.

Synthesis, characterization, biological studies, and molecular modeling of mixed ligand bivalent metal complexes of Schiff bases based on $N$-aminopyrimidine-2-one/2-thione

New mixed Schiff bases, Cu(II), Co(II), Ni(II), and Mn(II) complexes, were synthesized derived from 5-chloro-2-hydroxyacethophenone and 1-amino-5-benzoyl-4-phenyl-1H-pyrimidine-2-one/thione. These complexes were characterized by elemental analysis, magnetic measurements, molar conductivity, IR, electronic, NMR, and mass spectral studies. All the complexes showed nonelectrolytic behavior. Moreover, the newly synthesized mixed ligand complexes were evaluated for their in vitro antimicrobial efficiency against bacteria and yeast. The compound named Co(L$_{1}$L) had good antifungal activity against Candida species, but no profound antibacterial effect against bacterial strains. In addition, the ground state geometries of the complexes were optimized using a semi-empirical method at PM6 level, which is a suitable and effective basis set for organometallic and large structures to obtain information about their 3D geometries and electronic structures.

Multiple Linear Regression Solvatochromic Analysis of Donar-Acceptor Imidazole Derivatives

Catalytic synthesis of some polysubstituted imidazoles under solvent-free condition is reported and their characterization has been carried out spectral techniques. Electronic spectral studies reveal that their solvatochromic behavior depends both the polarity of the medium and hydrogen bonding properties of the solvents. Specific hydrogen bonding interaction in polar solvents modulated the order of the two close lying lowest singlet states. The solvent effect on absorption and emission spectral results has been analyzed by multiple parametric regression analysis. Solvatochromic effects on the emission spectral position indicate the charge transfer (CT) character of the emitting singlet states both in a polar and a non polar environment. The fluorescence decays for the imidazoles fit satisfactorily to a bi exponential kinetics. These observations are in consistent with quantum chemical calculations.

Nickel(ii) dithiocarbamate complexes containing the pyrrole moiety for sensing anions and synthesis of nickel sulfide and nickel oxide nanoparticles

Rare anagostic interaction is observed in (N-(pyrrol-2-ylmethyl)-N-furfuryldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(ii). Bis(N-(pyrrol-2-ylmethyl)-N-furfuryldithiocarbamato-S,S′)nickel(ii) is used for the preparation of spherical nickel sulfide and nickel oxide nanoparticles.

Synthesis, characterization and thermal degradation studies on some oxovanadium(IV) carbodithioates

Some oxovanadium(IV) carbodithioates of general formulae [VO(MorphcdtH)2B]SO4, [VO(4-RPipzcdtH)2B]SO4, [VO(4-EtPipzcdt)2B] (Morphcdt = morpholinecarbodithioate, Pipzcdt = piperazinecarbodithioate, R = M, Et and B = nil or Py) have been prepared and characterized by elemental analysis, TG/DSC, FTIR, electrospray mass spectral, conductance, NMR, solution electronic absorption spectral and variable temperature magnetic susceptibility measurement studies. All the complexes exhibit 1:1 electrolytic nature except [VO(4-EtPipzcdt)2B] which is a non electrolyte. Square pyramidal geometry and presence of superexchange interactions through bridging carbodithioate ligands for antiferromagnetic behaviour of complexes [VO(MorphcdtH)2]SO4, [VO(4-RPipzcdtH)2]SO4 and [VO(4-EtPipzcdt)2] have been proposed. Exchange interaction parameter, 2J = −124 to −83 cm−1 has been evaluated. Octahedral geometry for the pyridine adducts of oxovanadium(IV) carbodithioates has been proposed. Some of the complexes have also been screened for their antimicrobial activities against some pathogenic gram-negative bacteria, Escherichia coli, Enterobacter, Pseudomonasaeruginosa, Salmonella typhi, Shigella flexneri and gram-positive Staphylococcus epidermidis and Salmonella typhimurium using twofold serial dilution method. Minimum inhibitory concentration has been determined to fall in the range 31.25–250 μg mL−1.

Effect of gamma-irradiation on thermal decomposition kinetics, X-ray diffraction pattern and spectral properties of tris(1,2-diaminoethane)nickel(II)sulphate

Tris(1,2-diaminoethane)nickel(II)sulphate was prepared, and characterised by various chemical and spectral techniques. The sample was irradiated with 60Co gamma rays for varying doses. Sulphite ion and ammonia were detected and estimated in the irradiated samples. Non-isothermal decomposition kinetics, X-ray diffraction pattern, Fourier transform infrared spectroscopy, electronic, fast atom bombardment mass spectra, and surface morphology of the complex were studied before and after irradiation. Kinetic parameters were evaluated by integral, differential, and approximation methods. Irradiation enhanced thermal decomposition, lowering thermal and kinetic parameters. The mechanism of decomposition is controlled by R3 function. From X-ray diffraction studies, change in lattice parameters and subsequent changes in unit cell volume and average crystallite size were observed. Both unirradiated and irradiated samples of the complex belong to trigonal crystal system. Decrease in the intensity of the peaks was observed in the infrared spectra of irradiated samples. Electronic spectral studies revealed that the M–L interaction is unaffected by irradiation. Mass spectral studies showed that the fragmentation patterns of the unirradiated and irradiated samples are similar. The additional fragment with m/z 256 found in the irradiated sample is attributed to S8+. Surface morphology of the complex changed upon irradiation.

Studies on Oligomer Metal Complexes Derived from Bisamic Acid of Pyromellitic Dianhydride and 4-Bromoaniline.

Novel oligomer metal complexes (2a–f) of the ligand 2,5-bis((4-bromophenyl)carbamoyl) terephthalic acid (1) were prepared using transition metal salts and characterized by various spectroscopic techniques. The geometry of oligomer metal complexes was carried out by electronic spectral analysis and magnetic measurement studies. Polymeric properties have also been carried out. Ligand was synthesized using pyromellitic dianhydride and 4-bromoaniline. It was duly characterized. All novel synthesized compounds 1 and 2a–f were evaluated for their antibacterial and antifungal activity. The results showed significantly higher antibacterial and antifungal activity of oligomer metal complexes compared to the ligand.

Synthesis and characterization of Schiff base octaazamacrocyclic complexes and their biological studies

A condensation reaction between 1,2-diphenylethane-1,2-dione dihydrazone (DPEDDH) and dimethyl or diethyloxalate in methanol resulted in a novel Schiff base octaazamacrocyclic ligand, (L): (6,7,14,15-tetraoxa-2,3,10,11-tetraphenyl-1,4,5,8,9,12,13,16-octaazacyclohexadecane-1,3,9,11-tetraene). Subsequently metal complexes of the type [MLX2] and [CuL]X2; (M=Mn(II), Co(II), Ni(II) and Zn(II); X=Cl or NO3) were synthesized by the reaction of the free macrocyclic ligand (L) with the corresponding metal salts in 1:1 molar ratio. These complexes were characterized on the basis of analytical data, molar conductivity and magnetic susceptibility measurements, ESI-mass, IR, NMR (1H and 13C), EPR and electronic spectral studies. The thermal stability of the complexes was also studied by TGA and DTA analyses. These studies show that all the complexes have octahedral arrangement around the metal ions except copper complexes which are square planar. The ligand and its complexes were screened for their antibacterial activity in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and were also studied for their anticancer activity against the human cancer cells lines: HeLa (Human cervical carcinoma), MCF7 (Human breast adenocarcinoma) and Hep3B (Human Hepatocellular carcinoma). The recorded IC50 values for the tested compounds show moderate to good cytotoxicity against these cancer cell lines. The copper complex, [CuL]Cl2, showed excellent antimicrobial activity against tested microorganisms which is almost equivalent to the standard drug ciprofloxacin.

Binding interaction between 2-(naphthalen-1-yl)-1-p-tolyl-1H-phenanthro[9,10-d]imidazole and semiconductor nanomaterials

The binding interaction of bioactive phenanthrimidazole with nanoparticulate WO3, Fe2O3, Fe3O4, CuO, ZrO2 and Al2O3 has been studied by electronic and life time spectral studies. The phenanthrimidazole adsorbs strongly on the surface of nanosemiconductor, the apparent binding constants have been determined from the fluorescence quenching. In the case of nanocrystalline insulator, fluorescence quenching through electron transfer from the excited state of the phenanthrimidazole to alumina is not possible, but it is due to energy transfer process.

Synthesis, Characterization and Antifungal Activities of Adducts of Bis(O-isoamyldithiocarbonato)oxovanadium(IV) with Substituted Pyridines

A series of adducts of Bis(O-isoamyldithiocarbonato)oxovanadium(IV) with substituted pyridines have been synthesized by treating Bis(O-amyldithiocarbonato)oxovanadium(IV) with substituted pyridines in acetone in equimolar ratios. Analytical results show that the adducts have 1:1 stoichiometry with general formula VO(O-isoamyldithiocarbonato)2L where L = 2 and 3- bromopyridine; 4-acetylpyridine; 3-hydroxypyridine; 2-methoxypyridine; 2-amino-3-methylpyridine; 2- amino-4-methylpyridine; 2-amino-6-methylpyridine). The addition complexes have been characterized by elemental analysis, conductivity measurements, magnetic susceptibility measurements, infrared and electronic spectral studies. These studies suggest a distorted octahedral structure and paramagnetic nature of the adducts. Antifungal activity of some adducts have been carried out against the fungal strain Sclerotium rolfsii.

Synthesis and characterization of Ni(II) and Zn(II) complexes of (furan-2-yl)methyl(2-(thiophen-2-yl)ethyl)dithiocarbamate (ftpedtc): X-ray structures of [Zn(ftpedtc)2(py)] and [Zn(ftpedtc)Cl(1,10-phen)

Seven complexes of a new dithiocarbamate ligand (ftpedtc=(furan-2-yl)methyl(2-(thiophen-2-yl)ethyl)dithiocarbamate) namely [Ni(ftpedtc)2] (1), [Ni(ftpedtc)(NCS)(PPh3)] (2), [Ni(ftpedtc)(PPh3)2]ClO4 (3), [Zn(ftpedtc)2] (4), [Zn(ftpedtc)2(py)] (5), [Zn(ftpedtc)2(1,10-phen)] (6) and [Zn(ftpedtc)2(2,2′-bipy] (7) have been prepared. The complexes were characterized by IR, UV–Vis and NMR (1H and 13C) spectroscopy. Single crystal X-ray structural analysis was carried out for complexes 5 and [Zn(ftpedtc)Cl(1,10-phen)] (8). Electronic spectral studies suggest square planar geometry for nickel complexes. The 13C NMR peaks of the group N13CS2 are found in all the cases, at around 205.0ppm, which indicates the bidentate character of the dithiocarbamate ligand. X-ray structures of 5 and 8 show bidentate coordination by dithiocarbamate ligands and a distorted trigonal bipyramidal geometry for zinc, defined by NS4 and ClN2S2 donor sets, respectively. The packing in 8 involves π–π stacking interactions involving the 1,10-phenanthroline ring systems with the distance between ring centroids being 3.587Å.

Synthesis, Spectral, and Antimicrobial Studies of Nickel(II) Complexes With Nitrogen-Containing Ligands

Some nickel(II) complexes of 1,10-phenanthroline and 2,2′-bipyridine, associated with counterions such as Cl−, NO3−, OAc−, and SO42− have been synthesized and characterized by elemental analysis, conductance, spectral measurements, and antimicrobial studies. The conductance measurement indicates that [Ni(bipy)2H2O(NO3)](NO3), [Ni(phen)2(H2O)Cl]Cl·3H2O·CH3OH and [Ni(phen)3](NO3)2.4H2O are 1:1 and 1:2 electrolytes, respectively. The infrared and electronic spectral studies are consistent with the adoption of probable six-coordinate octahedral geometry for the complexes. The microbiostatic activity revealed that all the complexes showed pronounced activity against the tested fungi but little or no antibacterial activity. A six-coordinate octahedral geometry was established for [Ni(phen)2(H2O)Cl]Cl·3H2O·CH3OH using X-ray crystallography.

Spin-state-associated ligand distortion and complex solution equilibrium for a pair of Fe(II) pyridyl-imidazoline complexes

Reported herein are the magnetic and structural properties as well as solution equilibrium investigation for a pair of iron (II) pyridyl-imidazoline complexes: [Fe(pizMe)Cl2]2 (1) and [Fe(pizMe)3](FeCl4) (2), where pizMe=2-(2′-pyridinyl)-4,5-dihydro-1-methylimidazole. Dinuclear complex 1 contains high-spin iron (II) centers and a “flat” pizMe ligand (planar at the imidazoline N atom), while the pizMe-containing complex in 2 exhibits characteristics of a low-spin iron (II) center and a pyramidalized pizMe ligand. In solution, the two complexes are present in equilibrium as evinced through NMR and electronic absorption spectral studies. Spin-state switching between 1 and 2 in methanolic solution is a result of ligand lability.