Tetradentate Schiff Base Ligand Research Articles

Crystal structure and Hirshfeld surface analysis of 2,2'-{(1E,1'E)-[ethane-1,2-diylbis(aza-nylyl-idene)]bis-(methanylyl-idene)}bis-[4-(tri-fluoro-meth-oxy)phenol]copper(II) hydro-quinone hemisolvate.

In the title com-plex, [Cu(C18H12F6N2O4)]·0.5C6H6O2, the CuII ion has a square-planar coordination geometry, being ligated by two N and two O atoms of the tetra-dentate open-chain Schiff base ligand 6,6'-{(1E,1'E)-[ethane-1,2-diylbis(aza-nylyl-idene)]bis-(methanylyl-idene)}bis-[2-(tri-fluoro-meth-oxy)phenol]. The crystal packing is stabilized by intra-molecular O-H⋯O and inter-molecular C-H⋯F, C-H⋯O and C-H⋯π hydrogen bonds. In addition, weak π-π inter-actions form a three-dimensional structure. Hirshfeld surface analysis and two-dimensional fingerprint plots were performed and created to analyze the inter-molecular inter-actions present in the crystal, indicating that the most important contributions for the crystal packing are from F⋯H/H⋯F (25.7%), H⋯H (23.5%) and C⋯H/H⋯C (12.6%) inter-actions.

Yb(III), Sm(III) and La(III) complexes of a tetradentate pyridoxal Schiff base ligand: Their DNA-binding activity and bio-imaging applications

Yb(III), Sm(III) and La(III) complexes of a tetradentate Schiff base ligand, bis(pyridoxylidene)ethyelenediamine, are reported. Single crystal X-ray structures of the complexes reveal that in all the three complexes the Ln(III) ions are in a distorted dodecahedral geometry with N4O4-coordination environment provided by two coordinated ligands. Fluorescence spectroscopy shows that in the Yb(III) and Sm(III) complexes energy transfer from ligand centered excited state leads to population of an emissive f-f excited state. The complexes bind to ct-DNA, with high binding constant (Kb) comparable to those compounds (like ethydium bromide) which bind by intercalative mode. Cytotoxicity study shows that the complexes have quite low cytotoxicity towards HeLa cells. Further, they exhibited fast response, bright fluorescence and stability at physiological pH, making them suitable for use in fluorescence bio-imaging.

Tetradentate phenolic Schiff base ligands derived from aromatic diamine and their nickel (II) complexes: Synthesis, characterization, and in vitro anticancer screening

Two tetradentate phenolic Schiff base ligands namely 2,2'-((1E,1'E)-(1,2-phenylenebis(azanyl-ylidene))bis(methanylylidene))diphenol, L1H, 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis-(methanylylidene))bis(4-fluorophenol), L1F and their new nickel(II) complexes were successfully synthesized, characterized and evaluated for their in vitro anticancer activities against human colon cancer cell lines, HCT116. The compounds were characterized using FT-IR, 1H and 13C NMR, UV-Visible, elemental analysis and melting point. The anticancer results revealed that the parent ligands were more active than their corresponding complexes with L1F being the most potent anticancer compound with IC50 of 2.8 mg/ml.

Vanadium(IV) Schiff base Complex: Synthesis, Characterization, Crystal Structure and Thermal Decomposition into V2O5 Particles

Vanadium(IV) complex [VO((MeO-bph)2en)] (1), (MeO-bph)2en=N,N¢-bis(2-hydroxy-4-methoxybenzophenone)-1,2-ethanediamine, was synthesized and characterized by elemental analyses (CHN), FT-IR spectroscopy, thermogravimetry, SEM and single crystal X-ray diffraction. The title complex 1 was prepared by the reaction of VO(acac)2, 1,2-ethanediamine and 2-hydroxy-4-methoxybenzophenone (molar ratio 1:1:2). The single-crystal X-ray analysis of 1 shows that the vanadium(IV) ion is located in a distorted square pyramid (N2O3) environment with the tetradentate Schiff base ligand coordinated in equatorial positions and one oxygen atom in the axial position. Thermogravimetric analysis shows that the complex 1 decomposes in two stages. Finally, the complex was calcinated at 500 °C for 3 h and the V2O5 products characterized by FT-IR and SEM.

Synthesis, crystal structures, photoluminescence, electrochemistry and DFT study of aluminium(III) and gallium(III) complexes containing a novel tetradentate Schiff base ligand.

Single crystals of the aluminium and gallium complexes of 6,6'-{(1E,1'E)-[1,2-phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2-methoxyphenol), namely diaqua(6,6'-{(1E,1'E)-[1,2-phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2-methoxyphenolato)-κ4O1,N,N',O1')aluminium(III) nitrate ethanol monosolvate, [Al(C22H18N2O4)(H2O)2]NO3·C2H5OH, 1, and diaqua(6,6'-{(1E,1'E)-[1,2-phenylenebis(azanylylidene)]bis(methanylylidene)}bis(2-methoxyphenolato)-κ4O1,N,N',O1')gallium(III) nitrate ethanol monosolvate, [Ga(C22H18N2O4)(H2O)2]NO3·C2H5OH, 2, were obtained after successful synthesis in ethanol. Both complexes crystallized in the triclinic space group P-1, with two molecules in the asymmetric unit. In both structures, in one of the independent molecules the tetradentate ligand is almost planar while in the other independent molecule the ligand shows significant distortions from planarity, as illustrated by the largest distance from the plane constructed through the central metal atom and the O,N,N',O'-coordinating atoms of the ligand in 1 of 1.155 (3) Å and a distance of 1.1707 (3) Å in 2. The possible reason for this is that there are various strong π-interactions in the structures. This was confirmed by density functional theory (DFT) calculations, as were the other crystallographic data. DFT was also used to predict the outcome of cyclic voltammetry experiments. Ligand oxidation is more stabilized in the gallium complex. Solid-state photoluminescence gave an 80 nm red-shifted spectrum for the gallium complex, whereas the aluminium complex maintains the ligand curve with a smaller red shift of 40 nm.

Synthesis and structural characterization of three manganese(III) complexes with N2O2 donor tetradentate Schiff base ligands: Exploration of their catalase mimicking activity

Three manganese(III) complexes, [Mn(L1)(N3)(H2O)]·CH3OH·H2O (1), [Mn(L2)(N3)(H2O)] (2) and [Mn(L3)(H2O)2]ClO4 (3) {where H2L1 = N,N'-bis(3-methoxysalicylidene)1,2-ethanediamine, H2L2 = N,N'-bis(3-methoxysalicylidene)1,2-diamino-1-propene and H2L3 = N,N'-bis(3-methoxysalicylidene)1,2-propanediamine}, have been synthesized and characterized. Single crystal x-ray diffraction analysis confirmed their structures. Weak noncovalent interactions generate extended supra-molecular assemblies in all three complexes. Catalase mimicking activities (catalytic decomposition of hydrogen peroxide into oxygen and water) of the complexes have been investigated. Complex 3 catalyzes the decomposition of hydrogen peroxide most effectively. The higher catalase mimicking efficiency of complex 3 has been related to its structure.

Biomimetic catalytic activity and structural diversity of cobalt complexes with N3O-donor Schiff base ligand

This report describes the syntheses and structural characterizations of four new cobalt(III) compounds (1–4) derived from a tetradentate Schiff base ligand and their catalytic oxidation of different o-aminophenols in aerobic condition. X-ray crystal structural studies reveal that both pseudohalide ions and solvents used for the syntheses have significant influence on the structural diversity in these systems. All these compounds show the diverse catalytic activity towards the aerial oxidation of different o-aminophenols. As expected, the substitutionally labile coordination sites available for substrate binding is responsible for significantly higher catalytic activity of 1 and 2 then others. Literature reports reveal that although significant attention has been made to the catalytic oxidation of some substituted o-aminophenols in terms of the isolations and characterizations of their oxidised products with the native enzyme and its models, but the detailed kinetic studies were not available in the literature. Herein, we have examined the detailed kinetic studies of the aerobic oxidation of two substituted o-aminophenols, namely 2-amino-5-methylphenol and 2-amino-4-methylphenol, using 1 and 2 as catalysts. ESI mass spectrometry provides significant information to get insight into the mechanistic details and further disclose that the methyl substation in aromatic ring does not inhibit formation of the complex-substrate aggregate but it resulted the phenoxazine chromophore instead of phenoxazinone chormophore.

Colorful TiO2-x microspheres cooperating with titanium Schiff base complex for efficient visible light photocatalysts

As a promising photocatalyst, the large band gap of TiO2 imposes restriction on its light absorption in the visible region, making it less application in industrial fields. Herein, we design a facile solvothermal method to fabricate colorful defective TiO2-x microspheres with controllable morphological and porous structure, large specific surface area and tunable band gap on the basis of the Schiff base reaction between acetylacetone and ethylenediamine which produce bis(acetylacetone)ethylenediamine (acacen). The acacen, as a tetradentate Schiff-base ligand, has four binding sites which can stabilize titanium centers to produce titanium Schiff base complexes. The color of TiO2-x-Ti(acacen)y complexes changes from yellowish to brown and red with the variation of the acacen ligand, and the corresponding bandgap narrows from 3.25 eV to 2.16 eV as a result of the newly formed Ti3+ and oxygen vacancies (Vo) in the TiO2 lattice. In addition, red TiO2-x microspheres cooperating with titanium Schiff base complex demonstrate high photocatalytic efficiency in methylene blue under visible light as well as hydroxyl radical generation in contrast to yellowish TiO2 microspheres, revealing the significance of this strategy for morphological and bandgap manipulation in defective TiO2-x nanomaterials for high-performance photocatalysis.

Complexation of High-Valency Mid-Actinides by a Lipophilic Schiff Base Ligand: Synthesis, Structural Characterization, and Progress toward Selective Extraction.

Separation of U, Np, and Pu from used nuclear fuel (UNF) would result in lower long-term radiotoxicity, alleviating constraints on the storage and handling of the material. The complexity of UNF requires several industrial-scale processes with multiple waste streams. A one-step solution to the group removal of the elements, U-Pu, is desirable. Here we present a possible solution to group actinide separation utilizing the unique dioxy conformation of An(V/VI) cations and demonstrate the ability of a tetradentate lipophilic Schiff base ligand (L) to yield isostructural complexes of the general formula [(AnVIO2)(L)(CH3CN)] (where An = U, Np, or Pu). Extraction of An(VI) with the ligand follows the order U > Pu > Np, likely reflecting the decreased stability of the hexavalent actinide across the series. While the results indicate a promising path toward a one-step process, further improvement in the ligand stability and control of the redox chemistry is required.

A mononuclear cobalt(II) salophen-type complex: Synthesis, theoretical and experimental electronic absorption and infrared spectra, crystal structure, and predicting of second- and third-order nonlinear optical properties.

A tetradentate Schiff base ligand, (4-nitro-N,N'-o-phenylene-bis(5-methoxysalicylideneimine)) (H2L), and its cobalt(II) complex (CoL•DMF) were synthesized. Elemental analysis, and FT-IR and 1H NMR spectra were used to confirm the molecular structure of H2L ligand. In addition, elemental analysis, molar conductance measurement, infrared and electronic absorption spectroscopies as well as single crystal X-ray diffraction were employed to distinguish the molecular structure of the complex that has a slightly distorted square-planar geometry around the cobalt(II) ion. The geometries of H2L and CoL were optimized by means of the DFT/(U)PBE0/Def2-TZVP level of theory. Good agreement of the optimized geometric parameters of the complex with the corresponding experimental ones and successfully reproduction of the FT-IR spectra of the ligand and complex validated the applied method. Based on the optimized structure of CoL, its electronic absorption spectrum was reproduced by using time-dependent density functional theory (TDDFT) at the same level. Its analysis was carried out to assign the observed electronic transitions and determine their characters. The computed nonlinear optical (NLO) parameters (β, γ and < γ > values) of H2L and CoL by using TDDFT at the same level combined with the sum-over-states (SOS) method are considerable larger values than reference compound i.e. urea. The ligand and the complex in the absence of nitro and methoxy moieties referred to as H2L' and CoL' respectively were optimized to elucidate the effect of these moieties on hyperpolarizabilities values.

Syntheses, structures and electrochemical properties of ruthenium(II/III) complexes with tetradentate Schiff base ligands

Three unsymmetrical tetradentate Schiff base ligands, H2salipn, H2salipn-Br4 and H2salipn-Cl2, have been synthesized from the typical condensation reactions of treating 1,2-diaminopropane with salicylaldehyde, 3,5-dibromosalicylaldehyde and 5-chlorosalicylaldehyde, respectively. Treatment of [RuCl2(PPh3)3] with one equivalent of H2salipn or H2salipn-Br4 in the presence of triethylamine in tetrahydrofuran (THF) afforded the corresponding ruthenium(III) complexes [RuIIICl(PPh3)(salipn)] (1) and [RuIIICl(PPh3)(salipn-Br4)] (2). Interaction of [RuHCl(CO)(PPh3)3] with one equivalent of H2salipn-Cl2 or H2salipn-Br4 under the same conditions led to isolation of ruthenium(II) complexes [RuII(CO)(PPh3)(salalipn-Cl2)] (3) and [RuII(CO)(PPh3)(salalipn-Br4)] (4), respectively, in which one of the imine bonds was nucleophilically attacked by hydride to result in the formation of a mixed imine-amine ligand. The molecular structures of 1⋅1.5CH2Cl2, 2, 3⋅0.5CH2Cl2 and 4 have been determined by single-crystal X-ray crystallography. The electrochemical properties of 1–4 were also investigated. Their cyclic voltammograms displayed quasi-reversible Ru(IV)/Ru(III) and Ru(III)/Ru(II) couples with Eo ranging from 0.67 to 1.05 V and 0.74 to 0.80 V vs. Ag/AgCl (0.1 M), respectively.

Polyethyleneimine Nanofibers Functionalized with Tetradentate Schiff Base Complexes of Dioxomolybdenum(VI) as Efficient Catalysts for Epoxidation of Alkenes

AbstractThree tetradentate Schiff base ligands (H2L1‐3) were prepared from the reaction of 5‐sustituted‐2‐hydroxybenzaldehydes and 3,4‐diaminobenzoic acid. The obtained ligands were reacted with molybdenyl acetylacetonate in ethanol to prepare the corresponding dioxomolybdenum(VI) complexes (MoO2L1‐3) in good yields (80‐82%). Immobilization of the abovementioned complexes on polyethyleneimine (PEI) was achieved via condensation of carboxylic functional groups of the complex with amine functional groups of the polymer in presence of dicyclohexylcarbodiimide (DCC) and 4‐dimethylaminopyridine (DMAP). The obtained hybrid materials were then converted to electrospun nanofibers and used as recyclable catalysts for the epoxidation of alkenes.

Synthesis, crystal structure, experimental and theoretical studies of tetradentate N2O2 Schiff base ligand and its Ni(II) and Pd(II) complexes

The synthesis of a novel ligand bis(3-methoxysalicylidene)-4-methylbenzene-1,2-diamine (H2L) has been carried out by the condensation of 4-methylbenzene-1,2-diamine with 3-methoxysalicylaldehyde. The Ni(II) and Pd(II) Schiff base complexes have been synthesized from the reaction of Ni(OAc)2·4H2O and Pd(OAc)2 with the Schiff base ligand (H2L) in methanol and acetonitrile, respectively. The ligand and its complexes have been characterized by elemental analyses, FT-IR, 1H-NMR and UV–Vis spectroscopy. Moreover, the crystal structure of the ligand has been determined by single crystal X-ray crystallography. To have better understanding of electronic transitions of the ligand and its complexes, density functional theory (DFT) calculations have been performed. The geometries and electronic properties of the compounds have been obtained with the M062X level at Def2-TZVP basis set. Additionally, NBO analysis has been performed to interpret electronic transitions by determining their included occupied and virtual orbitals. The theoretical parameters confirmed the suggested structure of complexes. The spectroscopic data obtained from DFT calculations show acceptable agreement with the experimental results.

Effect different concetration and pH on complexes formation of New Tetradentate Schiff base Ligand

Effect different concetration and pH on complexes formation of New Tetradentate Schiff base Ligand

Enzymatic Activity and Photo-Kinetic Study of Cr(III), Mn(II), Co(II), Ni(II) and Cu(II) Complexes with Tetradentate

The Photo kinetic studies for five metal complexes of tetradentate Schiff base ligand were studied. These complexes were Chrome, Manganese, Cobalt, Nickle and Copper complexes. The kinetic values were achieved for the photoreaction and it referred to first order by in terms of complexes concentration. Three concentrations of these complexes to determined rate constant value which were determined by calculation the slope (-k) of relationship between radiation time on X-axis and natural logathirm of concentration changing on Y-axis. Values of rate constant were (0.0317min-1) for Cr-complex, (0.054min-1) for Mn-complex, (0.0706min-1) for Co-complex, (0.133min-1) for Ni-complex and (0.1211min-1) for Cu-complex. Relation between concentration on Y-axis and radiation time were showed the decreasing of concentration with time. Enzymatic study for the five complexes were achieved and showed that Cr-complex and Mn-complex showed competitive reactions and uncompetitive for Co-complex, Ni-complex and Cu-complex.

Synthesis, structural investigations and pharmacological properties of a new zinc complex with a N4-donor Schiff base incorporating 2-pyridyl ring

A tetradentate Schiff base ligand, L (L = N,N′-bis(1-(2-pyridyl)ethylidene)-2,2-dimethylpropane-1,3-diamine) was used in the preparation of a new mononuclear Zn(II) complex, [Zn(L)Cl]. The complex was structurally investigated by elemental analyses, spectroscopic studies and single crystal X-ray crystallography. Furthermore, to obtain insights into the structure, the ground state geometry of zinc complex cation was examined by dispersion corrected DFT method i.e. B3LYP-D3 within unrestricted scheme. Intermolecular contacts in the crystal structure were calculated and quantified by examination of Hirshfeld surface and fingerprint plots. In addition, the pharmacological properties of the newly synthesized complex were examined to explore the in vitro antibiofilm activity against P. aeruginosa, and anticancer activity against Human breast adenocarcinoma (MCF-7) cell line. Furthermore, molecular docking study was also recorded to find out various modes of virtual interactions between the zinc complex cation and the active site of receptor (PDB: 1gzt).

Nickel(II) and Copper(II) Complexes of a New Tetradentate Schiff Base Ligand: Synthesis, Characterization, Thermal Studies and Use as Precursors for Preparation of NiO and CuO Nanoparticles

A new tetradentate N2O2 Schiff base ligand (MeO-bph)2bn = N,N¢-bis(2-hydroxy-4-methoxybenzophenone)-1,4-butanediamine was prepared from the condensation of butane-1,4-diamine with 4-methoxy-2-hydroxybenzophenone and characterized by 1H-NMR spectroscopy and single-crystal X-ray diffraction. Its nickel(II) and copper(II) complexes characterized using elemental analyses (CHN) and IR spectroscopy. Thermogravimetric analysis of the Schiff base ligand and its Ni(II) and Cu(II) complexes revealed their thermal stability and decomposition pattern. Finally, the complexes were used for the preparation of NiO and CuO nanoparticles by solid-state thermal decomposition. The nanoparticles were characterized by FT-IR, XRD, and SEM. FT-IR and XRD confirmed the purity of the formed products NiO and CuO.

Highly Selective Solid Contact Sensor for Low Level Concentration Measurements of Iron(III) in Pharmaceutical and Biological Media

A symmetrical tetradentate Schiff base ligand was derived by the condensation of the corresponding o-vanillin with urea. The synthesized Schiff base ligand was studied to characterize its ability as a cation carrier in poly(vinylchloride) membrane solid contact sensor. The constructed sensor showed excellent response characteristics to iron(III) ion. The electrode exhibited Nernstian slope of 19.5 mV/decade over a wide concentration range of iron(III) from 3.0 × 10–6 to 1.3 × 10–2 M with a detection limit of 1.2 × 10–6 M. The sensor has fast response time, good reproducibility and excellent selectivity toward iron(III) ion with respect to many alkali, alkaline earth, transition and heavy metal ions. The potentiometric response of the sensor is independent of pH of the test solution in the range of 2.5–4.5. The applicability of the sensor was investigated by the determination of iron(III) concentration in pharmaceutical, biological and water samples.

Synthesis, characterization, crystal structure and DFT studies of a palladium(II) complex with an asymmetric Schiff base ligand

A Pd(II) complex of tetradentate Schiff base ligand, bis(5-methoxysalicylidene)-4-methyl benzene-1,2-diamine (H2L) was prepared from Pd(OAc)2 in refluxing acetonitrile. The complex was characterized using FT-IR, lH NMR, 13C{1H} NMR spectroscopic techniques, elemental analyses (CHN). Also, its molecular structure was determined by single-crystal X-ray diffraction. The crystal structure data showed a tetradentate mode of coordination for Schiff base, through N2O2 donor sets. In addition, DFT calculations at M06-2X/Def2-TZVP level of theory were conducted to obtain electronic and structural properties of the studied species. NBO-CMO analysis combined with TD-DFT method was done to interpret electronic transitions by determining their included occupied and virtual orbitals. NBO-CMO data show that there are MMCT and LMCT in the studied complex. All theoretical data are in line with the experimental results.

Nickel(II) complex with an asymmetric tetradentate Schiff base ligand: synthesis, characterization, crystal structure, and DFT studies

A new asymmetric tetradentate Schiff base, bis(5-methoxysalicylidene)-4-methylbenzene-1,2-diamine), H2L, and its Ni(II) complex were prepared and characterized using elemental analyses (CHN), FTIR, UV–Vis, 1H NMR, and 13C{1H} NMR spectroscopic techniques, and crystal structures of both were determined by X-ray crystallography. For both ligand and Ni(II) complex, density functional theory calculations to find geometry parameters, IR frequencies, electronic properties, and natural bond orbital analysis (NBO) were done with M062X method and Def2-TZVP basis set. All calculated data are consistent with the experiments. NBO data for the Ni(II) complex show that the main type of transition in UV-Vis is interligand charge-transfer, which is assigned as π-π*.