Template synthesis and physicochemical studies of 14-membered hexaazmacrocyclic complexes with Co(II), Ni(II), Cu(II) and Zn(II): a comparative spectroscopic approach on DNA binding with Cu(II) and Ni(II) complexes

A new series of 14-membered pendant arm hexaazamacrocyclic complexes of the type [MLX₂] · [M = Co(II), Ni(II), Cu(II) or Zn(II) for X = Cl; Co(II), Ni(II), Cu(II) or Zn(II) for X = NO₃] has been synthesized by metal template condensation of 1,2-phenylenediamine and 1,4-phenylenediamine with formaldehyde in methanol. The mode of bonding and overall geometry of these complexes have been deduced by elemental analyses, molar conductance values, FT-IR, ¹H-NMR, ¹³C-NMR, EPR, ESI-mass and UV–VIS along with magnetic measurement studies. The fluorescence and UV–VIS studies revealed a significant binding ability to DNA.     

Synthesis and spectroscopic studies on the Schiff base ligand derived from condensation of 2-furaldehyde and 3,3'-diaminobenzidene, L and its complexes with Co(II), Ni(II), Cu(II) and Zn(II): comparative DNA binding studies of L and its Cu(II) and Zn(II) complexes

The Schiff base ligand, N,N'-bis-(2-furancarboxaldimine)-3,3'-diaminobenzidene (L) obtained by condensation of 2-furaldehyde and 3,3'-diaminobenzidene, was used to synthesize the mononuclear complexes of the type, [M(L)](NO3)2 [M=Co(II), Ni(II), Cu(II) and Zn(II)]. The newly synthesized ligand, (L) and its complexes have been characterized on the basis of the results of the elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz, FT-IR, 1H and 13C NMR, mass, UV-vis and EPR. EPR, UV-vis and magnetic moment data revealed a square planar geometry for the complexes with distortion in Cu(II) complex and conductivity data show a 1:2 electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that Schiff base ligand, L and its Cu(II) and Zn(II) complex exhibit significant binding to calf thymus DNA. The highest binding affinity in case of L may be due to the more open structure as compared to the metal coordinated complexes.     

Magnetic,epr and SOD studies of some Cu(II)-Cu(II), Cu(II)-Ni(II) and Cu(II)-Zn(II) imidazolate bridged complexes

Magnetic, spectroscopic and superoxide dismutase activity of imidazolate bridged [(Salala)Cu-Im-Cu(Salala)]Na, [(Salala)Cu-Im-Zn(Salala)]Na and [(Salala)Cu-Im-Ni(Salala)]Na (Salala=Salicyledenealiniate, Im=Imdiazolate) are described. The epr and electronic spectra of related mononuclear complexes, viz., [(Salala)Cu-OH(2)] and [(Salala)Cu-ImH] also described. Appearance of a half-field signal in polycrystalline and decrease in mu(eff) per copper(II) ion indicate super exchange coupling between copper(II) ion in [(Salala)Cu-Im-Cu(Salala)]Na binuclear complex. A pH-dependent epr and UV-vis study of 50% aqueous DMSO solution of binuclear complexes suggest that the complexes are stable in narrow pH range.     

Smectic Cu(II), Pd(II) and VO(IV) complexes: synthesis, EPR and thermogravimetric studies

The octadecanoate of N(-(4-hexyloxyphenyl)salicylaldimine and the corresponding Cu(II), Pd(II) and VO(IV) complexes were synthesized and studied. The compounds were characterized by IR, 1H NMR, elemental and thermal analysis and polarized light microscopy. Thermogravimetric analysis and electronic spectra of the complexes are reported. Electron paramagnetic resonance (EPR) measurements were performed.     

Design,synthesis, DNA binding ability,chemical nuclease activity and antimicrobial evaluation of Cu(II), Co(II), Ni(II) and Zn(II) metal complexes containing tridentate Schiff base

A novel Schiff base has been designed and synthesized using the bioactive ligand obtained from 4-aminoantipyrine, 3,4-dimethoxybenzaldehyde and 2-aminobenzoic acid. Its Cu(II), Co(II), Ni(II), Zn(II) complexes have also been synthesized in ethanol medium. The structural features have arrived from their elemental analyses, magnetic susceptibility, molar conductance, mass, IR, UV–Vis, ¹H NMR and ESR spectral studies. The data show that the complexes have composition of ML₂ type. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion. The interaction of the complexes with calf thymus (CT) DNA has been studied using absorption spectra, cyclic voltammetric, and viscosity measurement. The metal complexes have been found to promote cleavage of pUC19 DNA from the super coiled form I to the open circular form II. The complexes show enhanced antifungal and antibacterial activities compared with the free ligand.     

New oxamato-bridged trinuclear Cu(II)-Cu(II)-Cu(II) complexes with hydrogen-bond supramolecular structures: synthesis and magneto-structural studies

Three oxamato-bridged copper(II) complexes of formula [(Cu(H(2)O)(tmen)Cu(tmen))(mu-Cu(H(2)O)(Me(2)pba))](n)((PF(6))(2))(n).2nH(2)O (1), [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(ClO(4))(2).4H(2)O (2), and [(Cu(H(2)O)(tmen)Cu(NCS)(tmen))(mu-Cu(H(2)O)(Me(2)pba))](2)(PF(6))(2).4H(2)O (3), where Me(2)pba = 2,2-dimethyl-1,3-propylenebis(oxamato) and tmen = N,N,N',N'-tetramethylethylenediamine, have been synthesized and characterized. Their crystal structures were solved. Complex 1 crystallizes in the monoclinic system, space group P2(1), with a = 15.8364(3) A, b =8.4592(2) A, c = 15.952 A, beta = 101.9070(10) degrees, and Z = 2. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.69530(10) A, b = 18.2441(3) A, c = 31.6127(5) A, beta = 90.1230(10) degrees, and Z = 4. Complex 3 crystallizes in the monoclinic system, space group P2(1)/c, with a = 6.68970(10) A, b = 18.150 A, c = 32.1949(4) A, beta = 90.0820(10) degrees, and Z = 4. The three complexes have a central core in common: a trinuclear Cu(II) complex with the two terminal Cu(II) ions blocked by N,N,N',N'-tetramethylethylenediamine. The structure of complex 1 consists of trinuclear cationic entities connected by hydrogen bonds to produce a supramolecular one-dimensional array. The structure of complexes 2 and 3 consist of trinuclear cationic entities linked by pairs by hydrogen bonds between the water molecule of the central Cu(II) and one oxygen atom of the oxamato ligand of the neighboring entity, forming a hexanuclear complex. The magnetic properties of the three complexes were studied by susceptibility vs temperature measurement. For complexes 1-3 the fit was made by the irreducible tensor operator (ITO). The values obtained were J(1) = -386.48 cm(-1) and J(2) = 1.94 cm(-1) for 1, J(1) = -125.77 cm(-1) and J(2) = 0.85 cm(-1) for 2, and J(1) = -135.50 cm(-1) and J(2) = 0.94 cm(-1) for 3. In complex 1, the coordination polyhedron of the terminal Cu(II) atoms can be considered as square pyramidal; the apical positions are filled by the oxygen atom from a water molecule in the former and a F atom of the hexafluorophosphate anion in the latter showing a quasi-planar [Cu(CuMe(2)pba)Cu] network. For complexes 2 and 3, the square pyramidal environment of the terminal Cu(II) ions was strongly modified. To our knowledge, this is the first time that the longest distance (apical) in complexes with oxamato derivatives and bidentate amines as blocking ligands has been reported in one of the oxamato arms. The great difference in J(1) values between 1 and the other two complexes is interpreted as an orbital reversal of the magnetic orbitals of the terminal Cu(II) ions in 2 and 3.     

Dehydration studies of Co(II), Cu(II) and Zn(II) methanesulfonates

The dehydration process of Co(II), Cu(II) and Zn(II) methanesulfonates was studied by thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) techniques in dynamic N₂ atmosphere. The TG/DTG curves show that all of them contain four crystallization water molecules, which are lost in two steps. The peak temperature and dehydration enthalpies ΔH were measured from DSC curves for each compound. The effect of procedural variables on the TG and DSC curves was investigated. In this work, the procedural variables included heating rate, Al pan state (unsealed and sealed) and sample mass.     

Synthesis, spectroscopic studies and crystal structure of the Schiff base ligand L derived from condensation of 2-thiophenecarboxaldehyde and 3,3'-diaminobenzidine and its complexes with Co(II), Ni(II), Cu(II), Cd(II) and Hg(II): Comparative DNA binding studies of L and its Co(II), Ni(II) and Cu(II) complexes

The Schiff base ligand, N,N'-bis-(2-thiophenecarboxaldimine)-3,3'-diaminobenzidine (L) obtained from condensation of 2-thiophenecarboxaldehyde and 3,3'-diaminobenzidine, was used to synthesize the complexes of type, [M2L2]Cl4 [M=Co(II), Ni(II), Cu(II), Cd(II) and Hg(II)]. The newly synthesized ligand (L) was characterized on the basis of the results of elemental analysis, FT-IR, 1H NMR, 13C NMR, mass spectroscopic studies and single crystal X-ray crystallography. The characteristic resonance signals in 1H NMR and 13C NMR spectra indicated the presence of azomethine group as a result of condensation reaction. The stoichiometry, bonding and stereochemistries of complexes were ascertained on the basis of results of elemental analysis, magnetic susceptibility measurements, molar conductance and spectroscopic studies viz., FT-IR, 1H and 13C NMR, UV-vis and EPR. EPR, UV-vis and magnetic moment data revealed an octahedral geometry for complexes with distortion in Cu(II) complex and conductivity data show 1:2 electrolytic nature of complexes. Absoption and fluorescence spectroscopic studies supported that Schiff base ligand L and its Co(II), Ni(II) and Cu(II) complexes exhibited significant binding to calf thymus DNA. The complexes exhibited higher affinity to calf thymus DNA than the free Schiff base ligand L.     

Thermal studies on Ni(II), Cu(II) and Pd(II) complexes of 6-amino-5-formyluracil and its N-methyl derivatives

The thermal behaviour of 6-amino-5-formyluracil (HFU), 6-amino-1-methyl-5-formyluracil (1-MFU), 6-amino-3-methyl-5-formyluracil (3-HFU) and 6-amino-1,3-dimethyl-5-formyluracil (HDFU) is described. Only HDFU is shown to contain crystallization water. Dehydration and fusion enthalpy values have been calculated from the DSC curves. Likewise, the thermal behaviour of new complexes obtained by reaction between the above pyrimidine derivatives and Ni(II), Cu(II) and Pd(II) ions is reported.     

Ternary Cu(II) complexes: synthesis,structural elucidation,and biological studies (DNA binding,cleavage, antibacterial,cytotoxicity)

Research on Chemical Intermediates - The present work focused on the assembly of 2-((2-(4-chlorophenylamino)phenylimino)methyl)-6-methoxyphenol as primary ligand (VBL) and bidentate nitrogen...     

Synthesis and spectral studies of pyranone derivative and its Cu(II), Co(II), Ni(II) and Zn(II) complexes

Under the thermolysis condition, 5-phenyl-2,3-dihydro-2,3-furandione (IV) in inert aprotic solvents as p-xylene at 130–140°C yields 3-benzoyl-4-hydroxy-6-phenyl-2H-pyran-2-one (VI) via phenyl ketene (V). The compound (VI) was converted into the corresponding 3-benzoyl-4-hydroxy-6-phenylpyridin-2(1H)-one (VII), and 3-benzoyl-2-oxo-6-phenyl-2H-pyran-4-yl acetate (VIII), by its reactions with ammonium hydroxyde, and acetic anhydride, respectively. On the other hand, a series of new various metal complexes (IX-XIa, XIb) of VI was synthesized. The results suggest that the compound VI as bidentate ligand indicate a binuclear structure for the Cu(II) complex with square-planar geometry. The Ni(II) and Zn(II) complexes are of tetrahedral and the Co(II) complex is also octahedral geometry with water molecules at the axial positions. The structures of compounds and complexes were characterized on the basis of elemental analysis, Mass, IR, ¹H, and ¹³C NMR spectra. The text was submitted by the authors in English.     

A trinucleating ligand based on 1,8-naphthalenediol: synthesis, structural and magnetic properties of a linear Cu(II)Cu(II)Cu(II) complex

The extension of Robson-type ligands from dinucleating based on 2,6-diformylphenol to trinucleating based on 2,7-diformyl-1,8-naphthalenediol is demonstrated by the synthesis, structural and magnetic characterization of the first trinuclear Cu(II) complex using a 1,8-naphthalenediol derived ligand.     

Thermogravimetric studies on some Cu(II) amine complexes

Thermogravimetric analysis of solid state bis-Cu(II) amine complexes CuL₂X₂, whereX=Cl^– or NO ₃ ^– andL=ethylenediamine (en), tetramethylethylenediamine (tmn),o-phenylenediamine (opd) and 2,2 bipyridyl (bpy), has been carried out and the kinetic parameters have been determined by fitting the observed mass losses corresponding to various steps using the Coats and Redfern equation. These studies show that the activation energies of these complexes decrease on changing the ligand in the order: bpy > opd > en > tmn. This trend can be attributed to the rigidity of the N-C-C-N skeleton in the bpy and opd ligands and steric crowding at the nitrogens in the tmn ligand. The majority of the decomposition steps were found to be composite in nature and frequently involved fractional groups expelled from the complexes. From the observation ofE _a> H, the thermal decomposition process of these complexes appears to be governed by the nucleation and growth mechanism.

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Zusammenfassung Kupfer(II)-bisaminkomplexe der Formel CuL₂X₂ mitX=Cl^– oder NO ₃ ^– undL=Äthylendiamin (en), Tetramethyläthylendiamin (tmn),o-Phenylendiamin (opd) und 2,2-Bipyridyl (bpy) wurden thermogravimetrisch untersucht und die kinetischen Parameter aus den gemessenen, zu den entsprechenden Schritten gehörenden Masseverlustwerten unter Anwendung der Gleichung von Coats und Redfern bestimmt. Es ergab sich, daß die Aktivierungsenergie dieser Komplexe entsprechend folgender Ligandenreihe abnimmt: bpy > opd > en > tmn. Dies kann bei den bpy und opd Liganden auf die Starrheit des N-C-C-N Fragmentes und im Falle der tmn Liganden auf eine räumliche Überfülltheit am Stickstoffatom zurückgeführt werden. Die Mehrzahl der Zersetzungsschritte sind komplexer Natur und haben häufig aus den Komplexen stammende Teilgruppen zum Ergebnis. Aufgrund der BeobachtungE _a>H scheint der thermische Zersetzungsvorgang dieser Komplexe durch einen Keimbildungs und -Wachstums mechanismus bestimmt zu werden.

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-() (II) CuL₂X₂, X = , aL= (en), (tmn),o- (opd) 2,2- (bpy). C - . , bpy\s>opd\s>en\s>tmn. N-C-C-N o- . , , . E _a H, , « ».

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A research grant from the University Grants Commission (India) to LSP and a JRF to JKK are thankfully acknowledged.     

DNA binding, nuclease activity and cytotoxicity studies of Cu(II) complexes of tridentate ligands

Cu(II) complexes of three tridentate ligands, L(1), L(2) and L(3), [L(1), N-((1H-imidazole-2-yl)methyl)-2-(pyridine-2-yl)ethanamine; L(2), N-((1-methyl-1H-imidazole-2-yl)methyl)-2-(pyridine-2-yl)ethanamine; L(3), 2-(pyridine-2-yl)-N-((pyridine-2-yl)methyl)ethanamine] respectively, were synthesized and characterized. The single crystal X-ray structure of complex 1 reveals the pseudo octahedral coordination geometry around the copper center. Absorption and fluorescence experimental evidence show good DNA binding propensity (in the order of 10(5) M(-1)) of the complexes. Thermal denaturation and circular dichroism (CD) analyses reveal minor structural changes of calf thymus (CT) DNA in presence of complexes and groove and/or surface binding of the complexes to CT-DNA. Kinetic DNA cleavage assay shows pseudo-first-order kinetic reaction between the complex and supercoiled (SC) DNA. In addition, mechanistic SC DNA cleavage results show higher DNA cleavage activity in presence of reducing agent, due to the presence of hydroxyl radicals. In vitro cytotoxicity assay of the complexes demonstrate that the complexes have low toxicity for different cancer cell lines and IC(50) values were between 37 and 156 μM.     

On the pH dependence of Cu(II) binding to insulin: ESR and electronic studies

The ESR and electronic absorption spectra have been used to investigate co-ordination of Cu(II) to insulin in aqueous solutions at different pH. Two series of complexes with low- and high copper content were examined and the values of the magnetic tensor components and the shape of the diffuse reflectance transitions suggested that these copper-insulin derivatives have tetragonal symmetry with Cu(II) in a (N_xO_y) ligand field, where oxygen donor groups are predominant at low pH and nitrogenous ligands at high pH. Such a trend was further supported by the presence of superhyperfine structure at pH = 13. Oxygen of the carboxylato groups, nitrogen of α- and ε-amino groups and of imidazoles, all contribute to the coordinations field. At very high pH only, a preferential binding site for Cu(II) is found, which probably involves deprotonated peptide nitrogens.     

Controllable synthesis, structures of amidecrownophane-type macrocycles and their binding ability toward anions

Amidecrownophane-type macrocycles with different number of hydroxy groups were prepared in quantitative yields by control of the conditions of thermal reaction with the aim to examine the role of hydroxy groups in anion recognition. It was proved that the hydroxy group played a critical role in anion binding for this type of macrocycles and the anion binding affinity could be tuned by different number of hydroxy groups. Further exploration clarified the presence of intramolecular hydrogen-bonding and exhibited the major effect on their anion binding potential.     

Synthesis and spectroscopic studies on complexes of N,N'-bis-(2-pyridinecarboxaldimine)-1,8-diaminonaphthalene (L); DNA binding studies on Cu(II) complex

The Schiff base ligand, N,N'-bis-(2-pyridinecarboxaldimine)-1,8-diaminonaphthalene (L), obtained by the condensation of 2-pyridinecarboxaldehyde and 1,8-diaminonaphthalene, has been used to synthesize the mononuclear complexes of the type [MLCl(2)] [M=Co(II), Ni(II), Cu(II) and Zn(II)]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of results of elemental analysis, molar conductance, magnetic susceptibility measurements, Job's method and spectroscopic studies viz., FT-IR, Mass, (1)H and (13)C NMR. The UV-vis and magnetic moment data revealed an octahedral geometry around Co(II), Ni(II) and Cu(II) ions and conductivity data show a non-electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that Cu(II) complex exhibits significant binding to calf thymus DNA.     

Spectroscopic studies on Co(II) and Cu(II) complexes of 6-amino-1-methyl-5-nitrosouracil and its 6-methylamine derivative

Four complexes are obtained during the reactions of 6-amino-1-methyl-5-nitrosouracil and its 6-methylamine derivative with Co(II) and Cu(II) ions. Theses complexes were characterized through their elemental, thermal analysis, infrared and 1H NMR spectroscopes. The obtained results indicate that, the exocyclic oxygen and nitrogen atoms are the most probable binding sites rather than ring nitrogen atoms. For cobalt complexes, the two pyrimidine bases act as bidentate ligands in the anionic form with the dissociation of iminic or N3 proton depending upon the nature of substituents on the pyrimidine ring. For copper complexes, the pyrimidine bases interact in the neutral form as monodentate ligands. Octahedral geometries are proposed for all of these complexes.