Antioxidant,Antimicrobial and Antitumor Studies of Transition Metal Complexes Derived from N-(2-Aminoethyl)-1,3-Propanediamine with DFT Calculations and Molecular Docking Investigation

New expected biologically active complexes for some of the first (Mn (II), Ni (II), Cu (II) and Zn (II)) and second (Rh (III) and Cd (II)) transitional metals rows with N-(2-Aminoethyl)-1,3-propanediamine as a ligand (AEPD)have been synthesized. All synthesized complexes were formed with 1:1 (metal: AEPD) stoichiometry except Ni (II) 1:2 (Ni: AEPD). The compounds were characterized by different analysis tools such as; elemental analysis, Fourier transform infrared (FTIR), ¹H-NMR, mass spectra, thermal analysis, electronic spectra, magnetic measurement and molar conductance techniques. AEPD ligand interacted with all metal ions as tridentate ligand by using the nitrogen atoms. On the other hand, density functional theory (DFT) calculations have been performed to confirm the optimized geometrical structures for both AEPD and its complexes. Furthermore, coordination compounds were screened for their potential antibacterial activities against six pathogenic bacteria as well as one kind of fungi in comparison to standard antibiotics by agar well diffusion method. The results show that most of the complexes exhibit antibacterial and antifungal activities against these organisms. Rh (III)-AEPD complex exhibited the strongest antibacterial effect followed by the Cd (II) complex but as antifungal agents Cd (II) was the first and the second was Rh (III). Also, the anticancer activity was screened for these metal complexes against growth of human liver cancer HEPG2 tumor cell line and this inhibition activity of Cd (II) chelate was noticed to be more active with lowest IC₅₀ than that of all other synthesized complexes. Unfortunately, Mn (II) and Rh (III) chelates lacked anticancer activity. The docking active sites interactions were evaluated using the selected protein for anticancer activity. Finally, antioxidant activity was studied. Mn (AEPD) showed maximum activity followed by complex of Rh (III).     

Antimicrobial studies of N - N ′-dicarboxydiethyloxamide and its Co(II), Ni(II), Cu(II) and Zn(II) complexes

Neutral complexes of Cu(II), Ni(II), Co(II), and Zn(II) have been synthesized from the oxamide-based ligand derived from leucine and diethyloxalate. The structural features have been deduced from their microanalytical, IR, UV/Vis, mass, ¹H and ¹³C NMR spectral data. The Co(II) and Ni(II) chelates have octahedral geometries and the Cu(II) chelate is a square-pyramidal geometry. The non-electrolytic and monomeric nature of the complexes is shown by their magnetic susceptibility and low conductance data. The biological activities of the ligand and its metal chelates against gram-positive and negative bacteria and fungi are also reported. All the compounds are antimicrobially active and show higher activity than the free ligand.     

Antimicrobial and antioxidant activities of new metal complexes derived from 3-aminocoumarin

3-Aminocoumarin (L) has been synthesized and used as a ligand for the formation of Cr(III), Ni(II), and Cu(II) complexes. The chemical structures were characterized using different spectroscopic methods. The elemental analyses revealed that the complexes where M=Ni(II) and Cu(II) have the general formulae [ML(2)Cl(2)], while the Cr(III) complex has the formula [CrL(2)Cl(2)]Cl. The molar conductance data reveal that all the metal chelates, except the Cr(III) one, are non-electrolytes. From the magnetic and UV-Visible spectra, it is found that these complexes have octahedral structures. The stability for the prepared complexes was studied theoretically using Density Function Theory. The total energy for the complexes was calculated and it was shown that the copper complex is the most stable one. Complexes were tested against selected types of microbial organisms and showed significant activities. The free radical scavenging activity of metal complexes have been determined by measuring their interaction with the stable free radical DPPH and all the compounds have shown encouraging antioxidant activities.     

Synthesis,characterization and antimicrobial screening of a novel organylborate ligand,potassium hydro(phthalyl)(salicylyl)borate and its Co(II), Ni(II), and Cu(II) complexes

A new organylborate ligand, potassium hydro (phthalyl) (salicylyl) borate and its Co(II), Ni(II), and Cu(II) complexes were synthesized. The compounds were characterized by elemental analysis, FTIR, ¹H NMR, ESI MS, UV–Vis techniques, molar conductivity and magnetic data measurements. The spectroscopic data support a distorted square planar geometry around the Cu(II) ion, while the Co(II) and Ni(II) ions acquire a distorted octahedral geometry. These synthesised compounds were also tested for their in vitro antimicrobial activities against some bacterial and fungal strains to assess their inhibiting potential and the activities shown by these complexes were compared with standard drugs. Results showed that there is a marked increase in the antibacterial and antifungal activities of the cobalt(II) complex than the free ligand and other complexes when treated against the same microorganism at the same concentration.     

New Coordination Compounds Based on a Pyrazine Derivative: Design,Characterization, and Biological Study

New coordination compounds of Mn(II), Fe(III), Co(II), and Ni(II) and the biologically active ligand L (N′-benzylidenepyrazine-2-carbohydrazonamide) were synthesized and characterized by appropriate analytical techniques: elemental analysis (EA), thermogravimetric analysis (TG–DTG), infrared spectroscopy (FTIR), and flame-atomic absorption spectrometry (F-AAS). The biological activity of the obtained compounds was then comprehensively investigated. Rational use of these compounds as potential drugs was proven by ADME analysis. All obtained compounds were screened in vitro for antibacterial, antifungal, and anticancer activities. Some of the studied complexes exhibited significantly higher activity than the ligand alone.     

Elaborated spectral,modeling, QSAR,docking, thermal,antimicrobial and anticancer activity studies for new nanosized metal ion complexes derived from sulfamerazine azodye

New azodye ligand (H₂L) and its relative Cr(III)-, Mn(II)-, Fe(III)-, Co(II)-, Ni(II)-, Cu(II)-, Zn(II)- and Cd(II)-nanosized complexes were prepared. A new synthesized compounds were characterized using spectral (mass, IR, UV–Vis, XRD, and ESR) and analytical (elemental, molar conductance, thermal and magnetic moment measurements) tools. Infrared spectra showed that the ligand behaves as a monobasic bidentate, coordinating with central atoms through carbonyl oxygen and α-hydroxyl group. The geometrical structures of Cr(III) and Fe(III) complexes were found to be in octahedral configuration, whereas Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes have tetrahedral forms. XRD patterns reflect an amorphous appearance of all investigated complexes. TEM images showed nanosized particles and identical distribution over the complex surface. Molecular modeling for the drug ligand and its metal ion complexes were performed using Gaussian09 program to assert on their structural formulae. Some essential parameters were extracted using HOMO and LUMO energies. AutoDock tools 4.2 was used to simulate the interaction process with infected cell proteins to expect the experimental pathway. The inhibition activity of drug ligand and its metal ion complexes was evaluated towards different types of bacteria and fungi through in vitro antimicrobial activities. The antitumor activities of all compounds are straightened towards human liver carcinoma (HEPG2) cell lines. Fe(III) and Co(II) complexes exhibited IC₅₀ of 2.90 and 4.23 µg mL^?1, respectively, which means they are more potent anticancer drug than the standard (doxorubicin, IC₅₀ = 4.73 µg mL^?1). Therefore, the two complexes may consider promising anticancer drugs.

     

Spectroscopic and mycological studies of Co(II), Ni(II) and Cu(II) complexes with 4-aminoantipyrine derivative

Complexes of the type [M(L)X(2)], where M = Co(II), Ni(II) and Cu(II), have been synthesized with novel NO-donor Schiff's base ligand, 1,4-diformylpiperazine bis(4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) which is obtained by the acid catalyzed condensation of 1,4-diformylpiperazine with 4-aminoantipyrine. The elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, UV, NMR, mass and EPR studies of the compounds led to the conclusion that the ligand acts as tetradentate chelate. The Schiff's base ligand forms hexacoordinated complexes having octahedral geometry for Ni(II) and tetragonal geometry for Co(II) and Cu(II) complexes. The mycological studies of the compounds were examined against the several opportunistic pathogens, i.e., Alternaria brassicae, Aspergillus niger and Fusarium oxysporum. The Cu(II) complexes were found to have most fungicidal behavior.     

Thermal degradation behaviour of some metal chelate polymer compounds with bis(bidentate) ligand by TG/DTG/DTA

Seven novel divalent transitional metal chelate polymers compounds (commonly known as chelate compounds or metal coordination complexes or polymer complexes) have been characterized by thermogravimetry (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA) methods. Thermal decomposition behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) polymers with terphthaoyl-bis(p-methoxyphenylcarbamide) has been investigated by thermogravimetric analysis (TGA) at heating rate 10 °C min^?1 under nitrogen atmosphere. TG/DTA of chelate compounds were shown to be a stable compound against thermal decomposition which was measured on the basis of final decomposing temperature, but it is observed in some curves that decomposition takes place at low temperature due to the lattice water, which is always placed at outer coordination sphere of the central metal ion. The presence of both lattice and coordinated water were noteworthy investigated in Co(II), Ni(II) and Cu(II) chelate polymer compounds, whereas lattice water found in Zn(II), Cd(II) and Hg(II). However, Mn(II) showed only coordinated water. Thermal stabilities for release of lattice water, coordinated water and organic moiety that occur in sequential decomposition of chelate compounds are explained on the basis of ionic size effect and electronegativity. The processes of thermal degradation taking place in seven chelate polymers were studied comparatively by TG/DTG/DTA curves which indicating the difference in the thermal decomposition. Coats–Redfern integral method is used to determine the kinetic parameters for the successive steps in the decomposition sequence of TG curves. Scanning electron microscope images of some chelate polymers were shown in previous publication revealed that particle sizes of chelate polymers were found to be of nanomaterial level therefore, resulting chelate compounds might be called as nanomaterial.     

Synthesis,spectral, and biological studies of transition metal chelates of N-[1-(3-aminopropyl)imidazole]salicylaldimine

Tridentate chelate complexes M[LX?·?2H₂O], where M?=?Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been synthesized from the Schiff base L?=?N-[1-(3-aminopropyl)imidazole]salicylaldimine and X?=?Cl. Microanalytical data, UV-Vis, magnetic susceptibility, IR, ¹H-NMR, mass, and EPR techniques were used to confirm the structures. Electronic absorption spectra and magnetic susceptibility measurements suggest square-planar geometry for copper complex and octahedral for other metal complexes. EPR spectra of copper(II) complex recorded at 300?K confirm the distorted square-planar geometry of the copper(II) complex. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species and one fungus. The electrochemical behavior of the copper complex was studied by cyclic voltammetry.     

1-苯基-3-甲基-4-苯甲酰基-5-吡唑啉酮与对氨基苯乙酮的缩合反应、量化计算和抑菌活性

利用1-苯基-3-甲基-4-苯甲酰基-5-吡唑啉酮(PMBP)和对氨基苯乙酮(PAAP)制备了PMBP缩对氨基苯乙酮(PMBP缩PAAP)及其铜(Ⅱ)、钴(Ⅱ)、镍(Ⅱ)和锌(Ⅱ)配合物,根据元素分析、红外、紫外、MS和1H NMR谱表征了结构.利用量子化学和分子力学计算方法对缩合反应的机理进行了探讨,较好地解释了PMBP-PAAP配体的烯胺酮式构型及其配合物的亚胺烯醇式构型.测定了化合物对大肠杆菌和金黄色葡萄球菌的抑制活性,其中以钴(Ⅱ)和铜配合物(Ⅱ)的抑菌活性最佳.     

Spectral,biological screening,and DNA studies of metal chelates of 4-[N,N-bis-(3,5-dimethyl-pyrazolyl-1-methyl)]aminoantipyrine

Tridentate chelate complexes of Co(II), Ni(II), and Cu(II) have been synthesized from 4-[N,N-bis-(3,5-dimethyl-pyrazolyl-1-methyl)]aminoantipyrine. Microanalytical data, UV-Vis, magnetic susceptibility, Infrared, ¹H- ¹³C-NMR, mass, thermal gravimetric analysis and electron paramagnetic resonance (EPR) techniques were used to confirm the structures. The electronic absorption spectra and magnetic susceptibility measurements suggest a distorted octahedral geometry for the metal. EPR spectra of the copper(II) complex at 77?K confirm the distorted octahedral geometry of the copper(II) complex. The antimicrobial activities of the ligand and metal complexes against the bacteria such as Xanthomonas maltophilia, Chromobacterium violaceum, Acinetobacter, Staphylococci, Streptococci, and the fungus Candida albicans have been carried out. A comparative study of minimum inhibitory concentration values of the ligand and its metal complexes indicates that metal complexes exhibit higher antibacterial and antifungal activity than the free ligand. The electrochemical behavior of copper(II) complex was studied by cyclic voltammetry. The complexes show nuclease activity in the presence of oxidant.     

Structure of (5656)macrotetracyclic chelates in the ternary systems M(II)-ethanedithioamide-acetone (M = Mn, Fe, Co, Ni, Cu, Zn) according to DFT calculations

The thermodynamic and geometric parameters of M(II) macrotetracyclic chelates (M = Mn, Fe, Co, Ni, Cu, and Zn) with the (NNNN) coordination of the donor ligand sites, formed by the complexation reactions of corresponding M(II) compounds, ethanedithioamide H₂N-C(=S)-C(=S)-NH₂, and acetone H₃C-C(=O)-CH₃ in gelatin-immobilized matrix implants have been calculated by the OPBE/TZVP density functional theory method with the use of the Gaussian 09 program package. The bond lengths and bond and torsion angles in these complexes have been reported. It has been shown that despite the fact that the MN₄ chelate core in them is almost planar, the five- and six-membered chelate rings are pronouncedly non-coplanar. In the Mn(II), Fe(II), Co(II), and Ni(II) complexes, these chelate rings are pairwise identical, whereas in the Cu(II) and Zn(II) complexes, they are noticeably different.     

Synthesis,Spectral, Modeling,Docking and Cytotoxicity Studies on 2-(2-aminobenzoyl)-N-ethylhydrazine-1-carbothioamide and its divalent metal complexes

2-(2-aminobenzoyl)-N-ethylhydrazine-1-carbothioamide (H₃L) and its Cu (II), Co (II), Ni (II) and Zn (II) complexes have been synthesized. The structures of the isolated compounds were suggested based on elemental analyses, spectral analyses (FTIR, ¹H and ¹³CNMR, MS, ESR and UV–Visible) and magnetic moments measurements. The free ligand exists in the keto-thione form, while in the metal complexes; it exists in the enol form and coordinates as mononegative bidentate via deprotonated enolic oxygen and N²H nitrogen. Both Co (II) and Ni (II) complexes have an octahedral, while Cu (II) complex has a square planar geometry. The compounds have direct electronic transitions with optical band gap (E_g) values in the range 3.14–3.40 eV. The ligand and its complexes were optimized using DFT/B3LYP methodology. The ligand optimization results supported the involvement of the carbonyl oxygen, thione sulfur and N²H hydrogen atoms in hydrogen bonding formation. Furthermore, the obtained structures of the ligand and its complexes were subjected to molecular docking study to predict interactions cause their cytotoxicity. Finally, the in vitro cytotoxicity activities of the ligand and its complexes were investigated against Hela and WISH cell lines where the Zn (II) complex exhibited higher activity than the other compounds against the two cell lines in accordance with molecular docking suggestion.     

A novel vic-dioxime ligand and its Ni(II), Cu(II) and Co(II) complexes containing calix[4]pyrrole moiety: synthesis, characterization and redox properties

A new calix[4]pyrrole functionalized vic-dioxime, 3-(4-methyl-9,9,14,14,19,19-hexaethylcalix[4]pyrrole)benzoaminoglyoxime (LH₂) was synthesized from anti-chloroglyoxime and 3-aminophenyl-calix[4]pyrrole at room temperature. The mononuclear complexes {nickel(II), copper(II) and cobalt(II)} of this vic-dioxime ligand were prepared and their structures were confirmed by elemental analysis, IR and UV–Vis spectrophotometry, magnetic susceptibility; the MS, ¹H and ¹³C NMR spectra of the LH₂ ligand and its Ni(II) complex were also recorded. The experimental results indicated that the ligand:metal ratio was 2:1 in the cases of Ni(II), Cu(II) and Co(II) complexes as is with most vic-dioximes. Electrochemical properties of the ligand, and its complexes were investigated in DMSO solution by cyclic voltammetry at 200?mV?s^?1 scan rate.     

Novel Schiff base metal complexes: synthesis,characterization, DNA binding,DNA cleavage and molecular docking studies

A novel Schiff base, 3-(((1H-1,2,4-triazol-3-yl)imino)methyl)-4H-chromen-4-one (L) was synthesized and used as ligand for the synthesis of Co(II), Ni(II), Cu(II), Zn(II) and Pd(II) complexes. The structural characterization of the ligand and its metal complexes was determined by using various physicochemical and spectroscopic methods. The IR data show that the Schiff base ligand acts as a bidentate donor coordinating through the oxygen atom of the chromone and nitrogen atom of the imine group. Based on all spectral data, tetrahedral geometry has been proposed for all the metal complexes except Cu(II) and Pd(II) complexes. However, square-planar geometry has been proposed for Cu(II) and Pd(II) complexes. DNA binding interaction of the ligand and its metal complexes was investigated by using UV–visible absorption, fluorescence and molecular docking studies. The binding constants were in the order of 10⁴ M^?1 suggesting good binding affinity towards CT-DNA. The DNA cleavage activity of the synthesized compounds was investigated by using agarose gel electrophoresis. In vitro antimicrobial activity of the synthesized compounds were screened against two gram-positive bacteria (Bacillus subtilis, Staphylococcus aureu) and two gram-negative bacteria (Escherichia coli, Proteus vulgaris) and one fungi strain Candida albicans using disc diffusion method. Antioxidant activity was carried out by DPPH radical scavenging method. In vitro anti-proliferative activity of the ligand and its metal complexes was also carried on the HEK-293, HeLa, IMR-32 and MCF-7 cancer cell lines using MTT assay.     

Synthesis,characterization, cyclic voltammetry,and antimicrobial properties of N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidine-1-yl)-malonamic acid and its metal complexes

A new heterocyclic compound, N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-malonamic acid, was synthesized from N-aminopyrimidine-2-one and malonyldichloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Ni(II), Mn(II), Zn(II), Cd(II), Fe(III), Cr(III), and Ru(III) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and conductometric analyses. Octahedral geometry was suggested for all the complexes, in which the metal center coordinates to ONO donors of the ligand. Each ligand binds the metal using C=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes were also discussed. The compounds were evaluated for their antimicrobial activities against Gram-positive and Gram-negative bacteria, and fungi using microdilution procedure. The antimicrobial studies showed that Cu(II), Fe(III), and Ru(III) complexes exhibited good antibacterial activity against Gram-positive bacteria with minimum inhibitory concentrations between 20 and 80 µg mL^?1. However, the ligand and the complexes possess weak efficacy against Gram-negative bacterium and Candida strains. As a result, we suggest that these complexes containing pyrimidine might be a new group of antibacterial agents against Gram-positive bacteria.     

Preparation of site-differentiated mixed ligand and mixed ligand/mixed metal metallacrowns

Assembly reactions that can prepare reliably regioselective metallamacrocyclic complexes have been a target in the development of metallacrowns. To this end, a series of mixed ligand and mixed ligand/mixed metal metallacrowns have been synthesized in high yield and structurally characterized. Two distinct connectivities have been observed in these types of metallacrowns. The monomeric, vacant metallacrown with mixed ligand composition [12-MC(Ni(II)N(Hshi)2(pko)2-4)] (1a) shows the connectivity pattern [-O-Ni-O-N-Ni-N-]2 while the other Ni metallacrowns, [12-MC(Ni(II)N(shi)2(pko)2-4)] (2a) and the coupled [12-MC(Ni(II)N(shi))2(pko)2-4)][12-MC(Ni(II)N(shi))3(pko)-4)] (3a) fused metallacrowns as well as the mixed metal Mn-Ni metallacrown [12-MC(Ni(II)Mn(III)N(shi)2(pko)2-4)] (4a), follow the pattern [-Ni-O-N-]4. Also, three distinct arrangements of the chelate rings around the metal ions have been observed. The syntheses are completely general, allowing for the substitution of different ligands into the metallacrown core. Compounds 1 and 4 show the 6-5-6-5-6-5-6-5 arrangement, compounds 2 and 3(1) the 6-6-5-5-6-6-5-5, and the 3(2) component the 6-6-5-5-6-5-6-5. The obtained structures can be rationalized by balancing the charge at each metal site in the metallacrown. Variable temperature magnetic susceptibility measurements show that exchange interactions for all the compounds are weak and dominantly antiferromagnetic (e.g., 2a gives an exchange coupling of J = -1.2 cm(-1) with g = 2.2). In solution, the metallacrowns are shown to be stable both to decomposition and ligand exchange.     

A new pyrimidine-derived ligand,N-pyrimidine oxalamic acid,and its Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) complexes: synthesis,characterization, electrochemical properties,and biological activity

A new heterocyclic compound N-(5-benzoyl-2-oxo-4-phenyl-2H-pyrimidin-1-yl)-oxalamic acid has been synthesized from N-amino pyrimidine-2-one and oxalylchloride. Bis-chelate complexes of the ligand were prepared from acetate/chloride salts of Cu(II), Co(II), Mn(II), Ni(II), Zn(II), Cd(II), and Pd(II) in methanol. The structures of the ligand and its metal complexes were characterized by microanalyses, IR, AAS, NMR, API-ES, UV-Vis spectroscopy, magnetic susceptibility, and thermogravimetric analyses. An octahedral geometry has been suggested for all the complexes, except for Pd(II) complex, in which the metal center is square planar. Each ligand binds using C(2)=O, HN, and carboxylate. The cyclic voltammograms of the ligand and the complexes are also discussed. The new synthesized compounds were evaluated for antimicrobial activities against Gram-positive, Gram-negative bacteria and fungi using the microdilution procedure. The Cu(II) complex displayed selective and effective antibacterial activity against one Gram-positive spore-forming bacterium (Bacillus cereus ATCC 7064), two Gram-positive bacteria (Staphylococcus aureus ATCC 6538 and S. aureus ATCC 25923) at 40–80 µg mL^?1, but poor activity against Candida species. The Cu(II) complex might be a new antibacterial agent against Gram-positive bacteria.     

Synthesis,characterization, DFT modeling and biological studies of new Co(II), Ni(II) and Cu(II) 4,6-bis(4-chlorophenyl)-2-amino-1,2-dihydropyridine-3-carbinitrile complexes

Three new metal complexes of 4,6-bis(4-chlorophenyl)-2-amino-1,2-dihydropyridine-3-carbinitrile (L) with Co(II), Ni(II) and Cu(II) were synthesized and characterized with physicochemical and spectroscopic techniques. The data suggest that (L) acts as a bidentate ligand bound to the divalent metal ions through amino N and carbinitrile N atoms having [M(L)₂(H₂O)₂]²⁺ formula (M = metal ions). The theoretical parameters, model structures, charges and molecular orbitals of all possible complexes have been determined using density functional theory. The energy gap of free ligand is ?E = 0.12565 eV, and this value is greater than energy gap of complexes, which indicates that the complexes are more reactive than free ligand. Also, ?E of Co(II) complex is lower than other complexes, which indicates that Co(II) complex is more reactive than Ni(II) and Cu(II) complexes. The antibacterial and antifungal activities of the ligand, metal salts and its complexes were tested against some microorganisms (bacteria and fungi). The complexes showed increased antibacterial and antifungal profile in comparison with the free ligand.     

Synthesis and spectroscopic studies of homo-binuclear, alkoxo bridged homo- and hetero-tetranuclear metal complexes of a bis-N2O4 Schiff base ligand derived from ethanolamine and macroacyclic tetranaphthaldehyde

Three new homo-binuclear Ni(II), Cu(II), Zn(II) complexes (2-4), homo-tetranuclear Cu(II) complex (5), and hetero-tetranuclear Cu(II)-Ni(II) complex (6) of a macroacyclic potentially bis-hexadentate N2O4 Schiff base have been synthesized. The imino-alcohol ligand, H4L was obtained by the condensation of ethanolamine with 2,2'-[2,3-bis(1-formyl-2-naphthyloxymethyl)-but-2-ene-1,4-diyldioxy]bis(naphthalene-1-carbaldehyde). The structures of both the Schiff base and its complexes have been proposed by elemental analyses, spectroscopic data i.e. IR, 1H and 13C NMR, UV-vis, electrospray ionisation mass spectra, molar conductivities and magnetic susceptibility measurements. The ligand has two similar compartments to bind first primary two metal ions, and acts bi- or tetra-negative, bis-tetradentate forming five membered chelate ring. However, secondary two metal ions (either Cu2+ or Ni2+) are ligated with dianionic oxygen atoms of the alcohol groups and are linked to the 1,10-phenanthroline-nitrogen atoms in the tetranuclear complexes (5 and 6).