Ligand Molar Ratio Research Articles

Experimental and theoretical studies of acetatodi(methylcyano)bis(O,O′-dialkyl and alkylene dithiophosphate)gadolinium(III) novel adducts

Seven novel Gd(OAc)[S2P(OR)2]2·2CH3CN and Gd(OAc)[S2P(OR′)2]2·2CH3CN gadolinium complexes where R=Et, n-Pr, n-Bu and Ph and R′=CH2CMe2CH2, CH2CEt2CH2, and CMe2CMe2 were synthesized and characterized by elemental analyses, Molecular weight determinations, IR and UV Visible spectroscopy. Micro analytical data revealed a 1:2 metal–ligand (O,O′-dialkyl and alkylene dithiophosphate) molar ratio in all complexes. Geometries were fully optimized at the Semi Empirical Sparkle PM6 level of theory and geometrical structures and electronic properties of the complexes were evaluated. The optimized geometries were confirmed to be minima on the potential energy surfaces through frequency calculations. Linear and nonlinear static optical susceptibilities for all complexes were calculated at the same level of theory. The absorption spectra of the complexes have been established using ORCA2.9 package utilizing the predicted optimized wave functions. The polarizability invariants were, in general, well-correlated with the molecular volume and the number of carbon atoms within the alkyl moieties. The largest electric properties were exhibited by the phenyl dithiophosphate complex.

Recovery of Cu(II) by chemical reduction using sodium dithionite: effect of pH and ligands.

Wastewaters containing Cu(II) and ligands are ubiquitous in various industrial sectors, and efficacy of copper removal processes, especially precipitation, is greatly compromised by ligands. Chemical reduction, being commonly employed for production of metal nanoparticles, is also effective for metal removal. Adjustment of pH and addition of ligands are important to control the particle size in metallic nanoparticle production. Exploiting the fact that ligands and metals coexist in many wastewaters, chemical reduction was employed to treat ligand-containing wastewater in this study. The experimental result shows that depending on pH, type of ligands, and copper:ligand molar ratio, copper could be removed by either the reduction or precipitation mechanism. Almost complete copper removal could be achieved by the reduction mechanism under optimal condition for solutions containing either EDTA (ethylenediaminetetraacetic acid) or citrate ligands. For solutions containing ammonia, depending on pH and Cu:ammonia molar ratio, copper was removed by both precipitation and reduction mechanisms. At pH of 9.0, formation of nano-sized particles, which readily pass through a 0.45 μm filter used for sample pretreatment before residual copper analysis, results in the lowest copper removal efficiency. Both cuprous oxide and metallic copper are identified in the solids produced, and the possible explanations are provided.

Kinetically stable metal ligand charge transfer complexes as crosslinks in nanogels/hydrogels: Physical properties and cytotoxicity

A terpyridine end-functionalized 8-arm poly(ethylene glycol) was prepared using the reaction of a 4′-aminopentanoxy substituted terpyridine with a p-nitrophenyl chloroformate activated PEG-(OH)8. Supramolecular complexation of the polymer terpyridine moieties by Fe2+ ions was investigated using NMR, UV–Vis and dynamic light scattering experiments. At low concentrations addition of Fe2+ ions to an aqueous solution of the polymer conjugate afforded nanogels with a single size distribution around 250nm. At concentrations above 3wt%, and at a 1:2 metal to ligand molar ratio, hydrogels were formed with increasing mechanical properties at increasing polymer concentrations. Using bovine chondrocytes, the biocompatibility and potential cytotoxicity of the polymer conjugate, nanogels and hydrogels were studied. The polymer conjugate with free ligands was toxic to the cells likely due to depletion of essential metal ions. When the terpyridine groups were complexed with Fe2+ ions, both nanogel suspensions and hydrogels showed no cytotoxicity in direct contact with chondrocytes. Indirect contact of gels with chondrocytes using transwells revealed the absence of toxic components by leaching. A Live-Dead assay on chondrocytes encapsulated in the hydrogels indicated that the hydrogels are cytocompatible, revealing the potential use of these materials for biomedical and pharmaceutical applications. Statement of SignificanceThe binding between transition metal ions and ligands with multiple binding sites can be almost as strong as covalent bonds. This metal–ligand charge transfer (MLCT) complexation was used to crosslink water soluble polymers into hydrogels. This approach to novel materials may find applications in the biomedical and pharmaceutical fields. Transition metal ions are essential trace elements present in tissue but up to now no cytotoxicity data of free ligands are available. Data presented show that free ligands are toxic to cells likely by depletion of trace metal ions, whereas kinetically stable complexes are not cytotoxic even when embedded in hydrogels. These results provide fundamental issues to be considered in the design of hydrogels crosslinked through metal ligand complexation.

Oxovanadium(iv) cations in heterometallic and heteroligand complex formation

The formation of heterometallic oxovanadium(iv) diethylenetriaminepentaacetates with titanium(iii), chromium(iii), cobalt(ii), nickel(ii), and manganese(ii) cations in aqueous solutions was studied by spectrophotometry and pH-metry. The stabilizing influence of heterometallic chelation on an unstable oxidation state of Ti iii and the labilizing effect of oxovanadium(iv) cations on the coordination of Cr iii cations by the carboxylate ligand anions in the heterometallic complex were shown. The optimum conditions for the formation of the heterometallic dtpa complexes were selected and their thermodynamic stability was estimated. The states of the oxovanadium(iv) cations in the monoand heteroligand systems involving polyamine, polyaminopolycarboxylate, and alkylpolyphosphonate ligands were studied. Specific features of ligand coordination and formation of the mixed-ligand chelates were investigated. A variety of molecular compositions of complex oxovanadium(iv) oxyethylenediphosphonate particles formed in ranges of pH 2.2—3.0, 4.5—5.5, and 6.3—6.4 was found. The preferability of formation of polynuclear oxovanadium(iv) oxyethylidenediphosphonates, viz., binuclear particles with oxovanadium(iv) cation to ligand molar ratios of 2 : 1 and 2 : 5 and trinuclear particles with a molar ratio of components of 3 : 2, was shown.

Spectroscopic study of copper(II) complexes with carboxymethyl dextran and dextran sulfate

The copper(II) ion complexes with carboxymethyl dextran (CMD) and dextran sulfate (DS) were studied by different methods. Content of copper was determined by atomic absorption spectroscopy. It was found that copper : ligand mole ratio (Cu : CMD) is 1 : 2, and Cu : DS is 1 : 1 by mole ratio method. Spectrophotometric parameters of synthesized compounds are characteristic for Cu(II) ion in octahedral (Oh) coordination. Analyzing of FTIR spectra in ν(C=O) vibration region has showed that -COOH group acts as bidentate ligand, while the compounds of Cu(II) with DS copper ions are in the region of four oxygen atoms of two adjacent sulfo groups. The presence of crystalline water was determined by isotopic substitution of H2O molecules with D2O molecules. Comparison of spectra recorded at room (RT) and liquid nitrogen temperature (LNT) has enabled detection bands of water molecules libration indicating that they are coordinated complementing coordination sphere of Cu(II) ions to six. The complexes are of Cu(II) · (CMD)2 · (H2O)2 or Cu(II) · DS · (H2O)2 type. The similarities of the γ(C-H) range in a part of FTIR spectra indicate that there is no difference in the conformation of the 4C1 glucopyranose (Glc) unit CMD and DS synthesized Cu(II) complexes.

Mass Spectrometric Analysis of Noncovalent Complexes Between Synthetic Peptides from Human Ribosomal Protein L7 and Protein G

In order to gain a comprehensive insight into the complexes of human ribosomal protein L7 with protein G in a certain degree, an investigation on the complexes of five synthetic L7 peptides, containing the basic-region-leucine-zipper (BZIP)-like domain (aa 15–49), with protein G was performed using nanoelectrospray ionization mass spectrometry (nanoESI-MS). Circular dichroism (CD) was used to characterize the secondary structures of L7 peptides. The characteristics of the complexes between L7 peptides and protein G were studied under various conditions, such as molar ratio of ligands, solvent condition, declustering potential, and peptide sequence. The stability of the complexes is found to decrease with increased declustering potential (>20 V), decreased pH (<5), increased pH (>5), while L7 peptide sequence had no obvious effect on the complex formation. Taken together, the complexes of L7 peptides with protein G are specific noncovalent binding with 1:1 stoichiometry. Because of the availability of synthetic L7 peptides, they might be used as baits to discover the binding partners of protein L7. Furthermore, the elaboration of the binding mechanisms of L7 peptides with protein G could benefit further application of protein G.

Design, spectral characterization, thermal, DFT studies and anticancer cell line activities of Co(II), Ni(II) and Cu(II) complexes of Schiff bases derived from 4-amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol

A series of two biologically active Schiff base ligands L1, L2 have been synthesized in equimolar reaction of 4-amino-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol with thiophene-2-carbaldehyde and furan-2-carbaldehyde. The synthesized Schiff bases were used for complexation with different metal ions like Co(II), Ni(II) and Cu(II) by using a molar ratio of ligand: metal as 1:1 and 2:1. The characterization of Schiff bases and metal complexes was done by 1H NMR, UV–Vis, TGA, IR, mass spectrometry and molar conductivity studies. The in DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. On the basis of the spectral studies an octahedral geometry has been assigned for Co(II), Ni(II) and Cu(II) complexes. The effect of these complexes on proliferation of human breast cancer cell line (MCF-7) and human hepatocellular liver carcinoma cell line (Hep-G2) were studied and compared with those of free ligand. The anticancer cell line results reveal that all metal complexes show moderate to significant % cytotoxicity on cell line HepG2 and MCF-7.

Supramolecular structure of azodye rhodanine compounds and their complexes: a review

The optical absorption properties of 5-(4′-derivatives phenylazo)-2-thioxothiazolidin-4-one (HLn) (where X = H) thin films have been studied. It was found that the values of the energy band gap, Eg, for derivatives were in the range of 1.77–2.29 eV depending on the nature of the substituent. The optical values of the energy band gap (Eg) for all derivatives near the absorption edge were found to be direct allowed transition. The synthesized ligands (HLn) (where X = H) were screened as antibacterial and antifungal agents. The proton–ligand dissociation constant of the rhodanine azo derivatives (HLn) (where X = H and X = P-OCH3Ph) and metal–ligand stability constants of their complexes with metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) have been determined potentiometrically in 0.1 M KCl. The stoichiometries of copper(II) and cadmium(II) complexes of HLn (where X = Ph) were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes. The molar ratio of ligand (HLn) (where X = H) and Ru(III) complexes is (1:2)/(1:3)(M:Ln), respectively. The study revealed octahedral geometry around Ru(III) complexes. A series of heterocyclic mixed ligands of oxovanadium(IV) complexes have been synthesized by the reaction of vanadium(IV) sulfate with rhodanine azo (HLn) (where X = H) in the presence of β-diketone (LH). Palladium(II) complexes of the general formula [Pd(Ln)L] (where LH = diketone = acetylacetone, HLn = azorhodanine) have been synthesized. In these complexes, the azo ligand acts as a monobasic bidentate ligand and is coordinated to the metal ion through the azo-nitrogen, enolic oxygen atoms forming stable six-membered heterocyclic rings. The D.C. electrical conductivity of HLn (where X = Ph) and their complexes were measured. The bond lengths and the force constants have been calculated for uranyl complexes (26–30) of HLn (where X = Ph). The plotting of r1, r2 and r3 (bond distance, rU–O) versus ν3 give a straight line with increasing the value of ν3 and decreasing rU–O.

Design, spectral characterization, DFT and biological studies of transition metal complexes of Schiff base derived from 2-aminobenzamide, pyrrole and furan aldehyde

A series of two biologically active Schiff base ligands L1, L2 have been synthesized in equimolar reaction of 2-aminobenzamide with pyrrol-2-carboxaldehyde and furan-2-carboxaldehyde. The synthesized Schiff bases were used for complexation with different metal ions like Co(II), Ni(II) and Cu(II) by using a molar ratio of ligand: metal as 2:1. The characterization of newly formed complexes was done by 1H NMR, UV–Vis, TGA, IR, mass spectrophotometry, EPR and molar conductivity studies. The thermal studies suggested that the complexes are more stable as compared to ligand. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. On the basis of the spectral studies an octahedral geometry has been assigned for Co(II) and Ni(II) complexes and distorted octahedral geometry for Cu(II) complexes. All the synthesized compounds, were studied for their in vitro antimicrobial activities, against four bacterial strains and two fungal strains by using serial dilution method. The data also revealed that the metal complexes showed better activity than the ligands due to chelation/coordination.

Design, Synthesis and Bioassay of Novel Metal Complexes of 3-Amino-6,8-Dibromo-2-Methyl Quinazolin-4(3H)-One

New ligand 3-amino-6,8-dibromo-2-methylquinazolin-4(3H)-one (L) has been synthesized in good yield by the reaction of methyl 3,5-dibromoanthranilate with acetic anhydride, followed by the replacement of oxygen with nitrogen of hydrazine. When the ligand reacts with Co(II), Zn(II), and Cu(II), new complexes are formed. The chemical structures of all prepared compounds were characterized by IR, elemental analysis, 1H NMR, 13C NMR, GC-MS, and UV/visible spectra; in addition, metal to ligand molar ratios M : L were determined. The free ligand and obtained metal complexes were tested in vitro against a number of microorganisms, including Gram positive bacteria (Staphylococcus aureus, Bacillus species and Enterococcus feacalis), Gram negative bacteria (Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa), and fungi (Candida albicans) in order to assess antimicrobial properties. All complexes showed considerable activity against all test bacteria.

Synthesis, Characterization, In-Vitro Antimicrobial and Antioxidant Activities of Co+2, Ni+2, Cu+2 and Zn+2 Complexes of 3-(2-(2-hydroxy-3-methoxybenzylidene)hydrazono)indolin-2-one

Four novel complexes of “3-(2-(2-hydroxy-3-methoxybenzylidene)hydrazono)indolin-2-one” have been synthesized with Co+2, Ni+2, Cu+2 and Zn+2. Physical and analytical techniques including CHN, IR, UV-Vis, AAS, molar conductivity values and magnetic susceptibility data were used to characterize all complexes. The bis Schiff base ligand i.e. 3-(2-(2-hydroxy-3-methoxybenzylidene)hydrazono)indolin-2-one, acted as a tridentate ligand and coordinated through phenolic oxygen, azomethine nitrogen and carbonyl group. Low values of molar conductance suggested the non-electrolyte nature of all complexes. Elemental analysis of complexes indicated the 1:1 metal to ligand mole ratios for [Cu(Inh)(OAc)] and [Zn(Inh)(OAc)] metal complexes and 1:2 metal to ligand mole ratios for [Co(Inh)2] and [Ni(Inh)2] metal complexes. Square planner geometry is proposed for [Cu(Inh)(OAc)] and distorted tetrahedral geometry is proposed for [Zn(Inh)(OAc)] while octahedral geometries are proposed for [Co(Inh)2] and [Ni(Inh)2] metal complexes. Antimicrobial and antioxidant studies were performed for all compounds and it was discovered that the complexes are more potent antibacterial and antifungal agents while the ligand exhibited comparatively more DPPH (1,1-diphenyl-2-picryl-hydrazil) radical scavenging activity than the complexes.

Oxocomplexes of Mo(VI) and W(VI) with 8-hydroxyquinoline-5-sulfonate in solution: structural studies and the effect of the metal ion on the photophysical behaviour.

Multinuclear ((1)H, (13)C, (95)Mo and (183)W) NMR spectroscopy, combined with DFT calculations, provides detailed information on the complexation between the Mo(VI) and W(VI) oxoions and 8-hydroxyquinoline-5-sulfonate (8-HQS) in aqueous solution. Over the concentration region studied, Mo(VI) and W(VI) oxoions form three homologous complexes with 8-HQS in water in the pH range 2-8. Two of these, detected at pH < 6, are mononuclear 1 : 2 (metal : ligand) isomers, with the metal centre (MO2(2+)) coordinated to two 8-HQS ligands. An additional complex, dominant at slightly higher pH values (5-8) for solutions with a 1 : 1 metal : ligand molar ratio, has a binuclear M2O5(2+) centre coordinated to two 8-HQS ligands. The two metal atoms are bridged by three oxygen atoms, two coming from 8-HQS, together with the M-O-M bridge of the bimetallic centre. We show that the long-range exchange corrected BOP functional with local response dispersion (LCBOPLRD), together with explicit solvent molecules, leads to geometries that readily converge to equilibrium structures having realistic bridging O8-HQS-M bonds. Previous attempts to calculate the structures of such binuclear complexes using DFT with the B3LYP functional have failed due to difficulties in treating the weak interaction in these bridged structures. We believe that the LCBOPLRD method may be of more general application in theoretical studies in related binuclear metal complexes. UV/visible absorption and luminescence spectra of all the complexes have also been recorded. The complex between Mo(vi) and 8-HQS is only weakly luminescent, in contrast to what has been observed with this ligand and many other metal ions. We suggest that this is due to the presence of low-lying ligand-to-metal charge transfer (LMCT) states close to the emitting ligand-based level which quench the emission. However, with W(VI), DFT calculations show that the LMCT states are now much higher in energy than the ligand based levels, leading to a marked increase in fluorescence.

One-step non-chromatography purification of a low abundant fucosylated protein from complex plant crude extract

Effective methods for isolation and purification of glycoproteins and other glycoconjugates are important to biopharmaceutical industry and diagnostic industry. They are also critical to an emerging field of glycoproteomics. In this work, we applied the newly-developed affinity ligand, a fusion protein of elastic like polymer (ELP) and a bacterial lectin, in an affinity precipitation process to purify soybean peroxidase (SBP) based on the presence of fucoseon the protein surface. We addressed, in particular, the challenge of purifying a low abundant protein from a complex dilute crude plant extract. The novel affinity precipitation developed in this work was very promising. One step binding and precipitation resulted in >95% recovery yield directly from crude extract and a 22.7 fold purification, giving a specific activity of 420 U/mg. The SBP isolated using this affinity precipitation meets or exceeds the quality specifications of reagent grade products by Sigma. We showed that the recovery yield had a strong dependence on the molar ratio of ligand to target fucosylated protein, with a ratio of three giving nearly full recovery, which could be predicted based on the total fucose content per protein molecule and the number of binding site per ligand molecule. We additionally developed a method of ligand regeneration and investigated its reuse. A simple wash with pH buffer was shown to be effective to regenerate the binding capacity for the ligand, and the ligand could be used for 10 times, giving an averaged 80% isolation yield based on initial input of soybean peroxidase. Taken together, an effective method of affinity precipitation was developed, which could be used to enrich a low abundant target glycoprotein from a complex mixture with a high recovery yield. The high selectivity for fucosylated protein and its ease of operation make this method particularly useful for purification of low abundant glycoprotein from natural sources. This work establishes a non-chromatography glycoform-specific purification method and extends the useful ELP-based affinity precipitation to glycoproteins.

The Use of Dihexyldithiocarbamate in Solvent Extraction of Transition Metals

Dialkyldithiocarbamates have long been used as chelating agents in solvent extraction of transition metals. In our previous study, an alkyl homolog of this type of ligand, namely dihexyldithiocarbamate (DHDTC), was synthesized and characterized. The use of this particular ligand in the extraction some selected transition metal ions is now reported for the first time. The effect of pH, of the metal to the ligand mole ratio, and of the variation in organic solvents, in the extraction of Fe3+, Ni2+, Cu2+, Cd2+, and Zn2+, were investigated. Results of the experiments showed that an extractability of about 44.62%, 58.15%, and 61.69%, respectively for Ni2+, Zn2+, and Cd2+ at pH 8 could be achieved. For Cu2+ and Fe3+ at pH 5 (69.96%) and pH 9 (81.29%). The metal to the ligand mole ratio for divalent transition metal, was 1:2 while trivalent was 1:3.

α, ω-Cholesterol-functionalized low molecular weight polyethylene glycol as a novel modifier of cationic liposomes for gene delivery.

Here, three novel cholesterol (Ch)/low molecular weight polyethylene glycol (PEG) conjugates, termed α, ω-cholesterol-functionalized PEG (Ch2-PEGn), were successfully synthesized using three kinds of PEG with different average molecular weight (PEG600, PEG1000 and PEG2000). The purpose of the study was to investigate the potential application of novel cationic liposomes (Ch2-PEGn-CLs) containing Ch2-PEGn in gene delivery. The introduction of Ch2-PEGn affected both the particle size and zeta potential of cationic liposomes. Ch2-PEG2000 effectively compressed liposomal particles and Ch2-PEG2000-CLs were of the smallest size. Ch2-PEG1000 and Ch2-PEG2000 significantly decreased zeta potentials of Ch2-PEGn-CLs, while Ch2-PEG600 did not alter the zeta potential due to the short PEG chain. Moreover, the in vitro gene transfection efficiencies mediated by different Ch2-PEGn-CLs also differed, in which Ch2-PEG600-CLs achieved the strongest GFP expression than Ch2-PEG1000-CLs and Ch2-PEG2000-CLs in SKOV-3 cells. The gene delivery efficacy of Ch2-PEGn-CLs was further examined by addition of a targeting moiety (folate ligand) in both folate-receptor (FR) overexpressing SKOV-3 cells and A549 cells with low expression of FR. For Ch2-PEG1000-CLs and Ch2-PEG2000-CLs, higher molar ratios of folate ligand resulted in enhanced transfection efficacies, but Ch2-PEG600-CLs had no similar in contrast. Additionally, MTT assay proved the reduced cytotoxicities of cationic liposomes after modification by Ch2-PEGn. These findings provide important insights into the effects of Ch2-PEGn on cationic liposomes for delivering genes, which would be beneficial for the development of Ch2-PEGn-CLs-based gene delivery system.

Dual-ligand affinity systems with octapeptide ligands for affinity chromatography of hIgG and monoclonal antibody.

This work reports the development of affinity systems with dual octapeptide ligands for affinity adsorption and purification of human IgG (hIgG) and monoclonal antibody (mAb). The three octapeptide ligands, FYWHCLDE (1), FYCHWALE (2), and FYCHTIDE (3), identified earlier by the biomimetic design strategy were used; any two of the three were mixed and coupled to Sepharose gel, leading to the formation of three dual-ligand affinity systems. Research emphasis was first placed on hIgG adsorption isotherms and the results were compared to the three single-ligand affinity systems. It was found that there was synergistic effect of the two peptide ligands in a dual-ligand system, so the affinity of a dual-ligand resin for hIgG was higher than those of its counterparts, single-ligand resins. Of the three dual-ligand systems, the FYWHCLDE (1)-FYCHTIDE (3) resin showed the highest affinity, so it was selected for investigating the effects of ligand density and molar ratio on hIgG adsorption equilibrium. It was found that the synergistic effect increased with increasing the total ligand density of the two peptides in the dual-ligand affinity system. Moreover, the FYWHCLDE (1)-FYCHTIDE (3) system at a molar ratio of 2:1 displayed the highest affinity for hIgG (0.69 μM at a total ligand density of 31.1 μmol/mL), indicating that the synergistic effect reached the maximum at this ratio. This dual-ligand affinity column was then used for the purification of hIgG and mAb by affinity chromatography, resulting in over 95% pure hIgG and mAb at recovery yield over 90%. Molecular docking of the two peptides to the Fc fragment simultaneously showed that FYWHCLDE (1) stood still but FYCHTIDE (3) shifted aside the CH2CH3 inter-domain. Molecular dynamics simulation of the binding process of the two octapeptides to Fc revealed that both the peptide ligands kept stable interactions with Fc. The synergistic effect of the dual-ligand affinity system was thus elucidated by the molecular simulations.

Electrochemical and spectral investigation of various pyridinedicarboxylic acids and their complexes with oxovanadium(IV) in dimethyl sulfoxide

The electrochemical behaviors of various pyridinedicarboxylic acids (pdcs),viz; 2,3-pdc, 2,4-pdc, 2,5-pdc, 2,6-pdc, 3,4-pdc, and 3,5-pyridinedicarboxylic acids only and their complexes with oxovanadium(IV) were investigated in 1:2 metal:ligand molar ratio in dimethylsulfoxide (DMSO) containing 0.2M sodium perchlorate (NaClO4) as a supporting electrolyte at a glassy carbon disc electrode (GCE) by means of cyclic voltammetry (CV). It is worth mentioning that all redox waves in pdc–oxovanadium(IV) complexes are attributed to pdc-ligand-centered redox reaction(s) because of the similarities of the cyclic voltammograms between free pdc ligands and the vanadyl complexes. CVs of the VO2+ complexes with these ligands have also shown that the cathodic peak potential shifts toward less negative potential, while the anodic peak potential becomes more negative as compared to the redox potentials of the respective ligand, clearly indicating that the reduction becomes easier on complexation. UVvisible spectra of the complexes have also been recorded in DMSO.

Synthesis and Toxicity Test Of Zinc (II) Pyridine-2,6-Dicarboxylate Complexes

Complexes of zinc (II) with pyridine-2,6-dicarboxylic acid were synthesized from a reaction between zinc(II) chloride and pyridine-2,6-dicarboxylic acid with two different methods. The first method was carried out by reflux method, mixing a certain mole ratio of metal and ligand in the mixed solution of methanol:water (1:1) as the solvent. The second method was carried out by employing a direct reaction of metal and ligand in a 1:2 mole ratio of the same solvent as it is of the first method. The first method yielded a small clear crystal grains shaped like parallelogram with the molecular formula of [Zn(H2dipic,dipic)Zn2(10H2O)]Cl4∙5H2O (Complex I-trinuclear). The second method yielded the colorless needle-like crystals and molecular formula [Zn(H2dipic)2Zn(H2O)5]Cl4∙2H2O (Complex II-dinuclear). Both complex compounds were tested their toxicity using Brine Shrimp Lethality Test (BSLT) method and obtained LC50 values of 989.26 and 503.32 ppm, respectively.

Cu(II) and Ni(II) Complexes of Novel Three 2-{1′-Phenyl-3′-(4″-Halophenyl)-1H-Pyrazole-4-yl}-1H-Benzimidazoles: Synthesis and Structural Depiction

Novel three 2-{1′-Phenyl-3′-(4″-halophenyl)-1H-pyrazole-4-yl}-1H-benzimidazoles (HBa–c) synthesized by the condensation of o-phenylenediamine and substituted-1H-pyrazole aldehydes in the presence of H2O2 through Ceric ammonium nitrate in catalytic amount and the nonchelated monodentate benzimidazoles complexes of 2-{1′-Phenyl-3′-(4″-halophenyl)-1H-pyrazole-4-yl}-1H-benzimidazoles were synthesized with a choice of metal salts in 2:1 mole ratio of ligand and metal salts, respectively, in ethanolic solution. The confirmed structures and characteristics of complexes were in good agreement with various physicochemical studies. The monodentate behavior of the ligands was proposed on the basis of spectral studies. The newly synthesized complexes possess octahedral and tetrahedral, square pyramidal and square planar geometry.

Influence of metal to ligand molar ratios on the supramolecular structure formation of Cu(II) with diaminopropane and iodide: Synthesis, structure, spectroscopic and DFT studies

Two new copper(II) complexes with 1,3-diaminopropane and iodide, viz., [{Cu ((1,3-diaminopropane)2 I (I3))}] (1) and [{Cu ((1,3 diaminopropane)2(I)2)}] (2) have been synthesized under self assembly conditions and structurally characterised to observe the structural variations brought about by varying ligand molar ratios, towards studying the effect of external factors on supramolecular structure formation, with a long term goal of obtaining magnetic materials. Corresponding to the variation in metal to ligand molar ratios from one to two, totally different products are obtained whose gross structural features are entirely different. The formation of 1, is unpredicted under given synthetic conditions and hence is interesting. The formation of 2, is as generally expected for the reacting components under given conditions. In case of 1, the metal ion’s choice to adopt a square pyramidal geometry by coordinating to two ligand units and a coordinated iodide, even in the absence of sufficient moles of ligand, as in 2, is due to sub-molar ligand ratios complemented by weak hydrogen bonding interactions, operating between the ligand amino hydrogens and coordinated iodide and uncoordinated triiodide moiety. This approach of providing sub-molar amounts of ligand to the metal to satisfy its coordination requirements, appear to be a promising strategy towards obtaining novel solid systems of material relevance. Both the complexes are characterised structurally and spectroscopically. Further, both the structures were satisfactorily modelled by calculations based on Density Functional Theory (DFT), and their UV–visible spectra were analyzed in depth with the help of Time Dependent DFT (TD-DFT).