Tetradentate Schiff Base Ligand Research Articles

Di-nuclear water-soluble oxovanadium (V) Schiff base complexes: Electrochemical properties and catalytic oxidation

Two dinuclear water-soluble oxovanadium (V) complexes [(L1H)VO(μ-O)]2 (C1) and [(L2H)VO(μ-O)]2 (C2) were prepared from VOSO4 and the corresponding tetradentate Schiff base ligands [N-(2-hydroxyethylamino)ethyl]-5-methoxysalicylaldimine (L1H) and 2-[(2-(2-hydroxyethylamino) ethylimino)methyl] phenol (L2H) in refluxing methanol. Their catalytic performance in the oxidation of olefins was explored in water as green solvent using different oxidant agents. Our results demonstrate the effectiveness and good yield of the catalysts by ensuring its effective reusability. The electrochemical behaviour of oxo-vanadium complexes were investigated using cyclic voltammetry (CV). The results showed that complexes exhibit one-electron transfer coupled with the electrochemical irreversibility of the process (ErCi mechanism) corresponding to the VOIV/VOV. The irreversibility behavior of the complexes was showed with the scan rate growing and deformation of peaks.

Cyclometalated Pt(II) complexes with tetradentate Schiff base ligands: Synthesis, photophysics, electrochemical studies and optical power limiting performance

Pt(II) complexes with tetradentate Schiff base ligands (Pt-1–Pt-5) were prepared, and their detailed photophysics were studied using steady-state, transient spectroscopies and density functional theory systematically. Pt-1–Pt-5 all exhibit 1π,π* transitions and metal-to-ligand/intraligand charge transfer transitions in the UV–vis region. Meanwhile, these complexes are emissive in solution at room temperature (λem = 400–800 nm, Φem = 0.008–0.196). Triplet transient absorption (TA) demonstrated that except Pt-3, all complexes exhibit broad and strong triplet excited-state absorption from 400 to 750 nm. What's more, nonlinear transmission experiment demonstrated that Pt-1–Pt-5 show robust reverse saturable absorption (RSA) at 532 nm ns laser pulses. Among them, Pt-5 shows the strongest nonlinear absorption performance, which could potentially be used as optical power limiting (OPL) materials.

Thermal Studies of Iron (II) Schiff Base Complexes: New Precursors for Preparation of α-Fe2O3 Nanoparticles via Solid-State Thermal Decomposition

In this research study, four iron (II) complexes of tetradentate N2O2 Schiff base ligands with the general formula of Fe((MeO-bph)2 Am) (Am=1,2-ethyelenediamine (1), 1,3-propanediamine (2), 1,4-buanediamine (3) and 2,2-dimethyl-1,3-propanediamine (4) were synthesized and characterized using the elemental analysis (CHN) and FT-IR spectroscopy. Thermal properties and decomposition stages of all the complexes were evaluated. Finally, all complexes were decomposed at 600 °C for 3 h and the dark precipitates were characterized using the FT-IR, XRD and SEM. FT-IR and XRD results revealed that the precipitate were the pure phase of rhombohedral of magnetite (α-Fe2O3) nanoparticles. The SEM images showed that, the morphology of the precipitate was a relatively spherical shape and average diameter of 40-70 nm. The results of the thermogravimetric analysis the iron (II) complexes showed that the complexes 1–4 were stable until 140-200 °C. However, after that, all the complexes 1–4 decomposed in two stages at various temperatures.

Synthesis and Testing of The Antibiotic Properties of Schiff Base Ligands and Their Cobalt Complexes

The ability to design and synthesize new antibiotic compounds has become necessary in recent years due to the emergence of antibiotic resistant bacteria from such species as E. coli, K. pneumoniae, and S. aureus, among others. Schiff base ligands and their metal complexes, namely those complexes formed with cobalt (II), have displayed promising potential as a means to synthesize new compounds for antibiotic use in a straightforward and efficient manner. Specifically, cobalt complexes of tetradentate Schiff base ligands have been shown to be effective against both Gram‐positive and Gram‐negative bacterial strains (Shaheen et al., 2019); however, there is as of yet limited information as to how a variety of specific bacterial strains will be affected by such compounds. This project is centered on the synthesis of Schiff base ligands from O‐phenylenediamine and various salicylaldehyde precursors in order to form tetradentate complexes and to test their antibiotic properties through the Kirby‐Bauer disc diffusion test. The proper synthesis of the Schiff base ligands is currently be confirmed by NMR, IR, and MS analysis. Following this confirmation, we will add cobalt acetate to facilitate metal complex formation and confirm expected complexing by Microwave Plasma‐Atomic Emission Spectrometry (MP‐AES), cyclic voltammetry, and Electron Spin Resonance (ESR) analyses. Overall, we expect that this project will shed new insights on the specific antibacterial range for these cobalt Schiff base complexes as well as the efficacy of these complexes as effective antibiotics for general medical use.

Bioconjugates of Co(III) complexes with Schiff base ligands and cell penetrating peptides: Solid phase synthesis, characterization and antiproliferative activity

In this work we synthesized a chelating Schiff base by a single condensation of salicylaldehyde with 3,4-diamino benzoic acid (1). This ligand was used further for complexation to CoCl2·6H2O under nitrogen. In the next step, three six-coordinate Co(III) complexes were synthesized by coordinating this complex with imidazole (2), 2-methyimidazole (3) and N-Boc-l-histidine methyl ester (4) (Boc: tert.-butoxycarbonyl) in axial positions with simultaneous oxidation of Co(II) to Co(III) under ambient environment. All Co(III) complexes were characterized by multinuclear NMR spectroscopy (1H, 13C and 59Co NMR), FT-IR, mass spectrometry and HPLC. The Co(III) complexes were conjugated to three different cell penetrating peptides: FFFF (P1), RRRRRRRRRGAL (P2) and FFFFRRRRRRRRRGAL (P3). Standard solid-phase peptide chemistry was used for the synthesis of cell penetrating peptides. Coupling of N-terminal peptides with the cobalt complexes, possessing a carboxylic group on the tetradentate Schiff base ligand, afforded Co(III)-peptide bioconjugates, which were purified by semi-preparative HPLC and characterized by analytical HPLC and mass spectrometry. The antiproliferative activity of the synthesized compounds was studied against different human tumour cell lines: lung cancer A549, liver cancer HepG2 and normal human fibroblasts GM5657T, in comparison with the activity of cisplatin as a reference drug. The bioconjugate 21 containing the Co complex 4 and the combined phenylalanine and polyarginine cell penetrating sequence P3 shows better activity against the liver cancer line HepG2 than the parent Co(III) complex 4.

Direct determination of monosaccharides in honey by coupling a sensitive new Schiff base Ni complex electrochemical sensor and chemometric tools

The determination and quantification of saccharides is of considerable importance in the food industry among other fields. In this work, we describe for the first time the preparation of the Schiff base Ni complex, NiII-(N,N’-bis(2,3-dihydroxybenzylidene)-1,2-diaminobenzene) (Ni(II)-2,3dhS) obtained by reaction of the tetradentate Schiff base ligand containing ortho quinone functional groups (N,N’-bis(2,3-dihydroxybenzylidene)-1,2-diaminobenzene) and Ni2+, as well as its application in the development of an electrochemical sensor. Coupled to chemometric tools, the sensor allowed the direct determination of glucose and fructose in honey, without the need of previous separation steps or chromatographic techniques. For this purpose, the new Schiff base Ni complex has been electropolymerized onto screen-printed electrodes modified with carbon nanotubes. The electropolymerization process has been exhaustively characterized by operando spectroelectrochemical techniques to confirm the generation of the desired polymer. The resulting modified electrodes present a strong electrocatalytic activity towards the oxidation of glucose and fructose in alkaline solution and have been employed in combination with partial least squares regression (PLSR) to resolve mixtures of glucose and fructose in a complex matrix, as honey. The multivariate model was based on PLSR analysis and showed good predictive capability for the two analytes in sample standard honey with an average error of 8% and relative standard deviations below 9%.

Synthesis, crystal structure, and characterization of two Cu(II) and Ni(II) complexes of a tetradentate N2O2 Schiff base ligand and their application in fabrication of a hydrazine electrochemical sensor

Two new Cu(II) and Ni(II) complexes of a tetradentate N2O2 Schiff base ligand (H2L = N,N'-bis-(4-hydroxysalicylidene)-ethylenediamine) were synthesized. The structures of the H2L ligand and its complexes (1 and 2) were unambiguously determined by elemental analysis, FT-IR, 1H NMR, and UV–Vis spectroscopy. The crystal structures of the complexes were also determined by X-ray crystallography technique. In addition, the complexes were tested as a modifier for a glassy carbon electrode (GCE) to prepare an electrochemical sensor for detection of hydrazine in real samples. The prepared sensor with Ni(II) complex showed admirable sensitivity and selectivity for determination of hydrazine at 0.55 V without any interference of other common substrates. A dynamic linear range of 0.5–150 µM with a detection limit (LOD) of 166.66 nM and sensitivity of 0.1174 μA µM−1 cm−2 was achieved. The obtained LOD was much lower than that specified in the U.S. Environmental Protection Agency (EPA) regulations. The prepared sensor was also successfully applied to detect hydrazine in Tehran’s Jajrood river water as a real sample.

Easy coordinate geometry indexes, τ4 and τ5 and HSA study for unsymmetrical Pd(II), Fe(II), Zn(II), Mn(II), Cu(II) and VO(IV) complexes of a tetradentate ligand: Synthesis, characterization, properties, and antioxidant activities

In this study, versatile multifunctional Schiff base derivative and its metal complexes were synthesized and characterized by 1H, 13C NMR, UV–vis, IR, CHN analysis, Mass spectra, m.p. and X-ray diffraction. The tetradentate Schiff base H2L was synthesized using a microwave-assisted method. Metal complexes [M = Pd (1), Zn (2), Cu (3), Fe (4), Ni (5) Mn (6) and V(O) (7)] were prepared using mild conditions. Their antioxidant activities were assessed by four different methods (DPPH, FTC, HRSA, and H2O2 SA). The antioxidant results revealed that these compounds have moderate to good activities against the BHA which was used as a standard or a positive control. The crystal and molecular structures of H2L, 1, 2 and 7 have been determined by X-ray diffraction on single crystals with Hirshfeld surfaces and fingerprint plots analysis facilitating a comparison of intermolecular interaction. H2L possesses intra-molecular hydrogen bonds. In the complexes, the tetra dentate Schiff base ligands (ONNO) forms a heterocyclic base plane of a distorted square-pyramidal coordination geometry in 1, 2 and 7. Interestingly, only the enol-imine tautomeric form was confirmed by various techniques as an EE isomer. Geometric parameter for four and five-coordinate complexes, τ4 and τ4 for quantitatively evaluating the geometry of the complexes are presented.

Dinuclear Zn(II) and tetranuclear Co(II) complexes of a tetradentate N2O2 Schiff base ligand: Synthesis, crystal structure, characterization, DFT studies, cytotoxicity evaluation, and catalytic activity toward benzyl alcohol oxidation

Two novel dinuclear Zn(II) and tetranuclear Co(II) complexes of a tetradentate N2O2 Schiff base ligand (H2L = N,N′‐bis‐(4‐hydroxysalicylidene)‐1,3‐diaminopropane) were prepared. The structures of the H2L ligand, [4(Zn2L(μ‐O2CCH3)(O2CCH3)(H2O))]⋅4CH3OH⋅3H2O (complex 1) and [Co4L2(μ‐O2CCH3)2(O2CCH3)2]⋅2H2O (complex 2) were unambiguously characterized by elemental analysis, mass spectrometry, Fourier‐transform infrared spectroscopy (FT‐IR), 1H nuclear magnetic resonance (NMR), and UV–Vis spectroscopy. Single crystal X‐ray diffraction studies revealed that two Zn(II) nuclei of 1 were connected through μ‐phenolato and μ‐acetato bridges and had distorted square pyramidal and distorted octahedral coordination geometries. Four Co(II) nuclei of 2, on the contrary, showed a Co4O4 cubane‐like configuration in which Co(II) cations and O atoms were located at alternating corners of a distorted cube. Density functional theory studies at the B3LYP/6–31 G(d) level were carried out to gain an insight into the thermodynamic stability of the complexes. in vitro cytotoxicity of the ligand and the complexes were evaluated using the MTT assay against breast cancer MCF7 cells, melanoma cancer A375 cells, and prostate cancer PC3 cells as representative human cancer cell lines. Complex 1 showed a remarkable activity against A375 and PC3 cancer cell lines. In addition, 1 and 2 were used as precursors to produce zinc and cobalt oxide nanoparticles via pyrolysis technique. The resulting ZnO and Co3O4 nanoparticles were characterized using FT‐IR spectroscopy, UV–Vis diffuse reflectance spectroscopy, powder X‐ray diffraction, and field emission scanning electron microscopy. Then, these nanoparticles were used as heterogeneous catalysts in the oxidation of benzyl alcohol with hydrogen peroxide at room temperature. Both catalysts showed good recyclability with a negligible decrease in their efficiency during four catalytic cycles. The results of theoretical calculations showed that the most stable product was benzaldehyde, which is in good agreement with the obtained experimental results.

Cobalt complexes containing salen-type pyridoxal ligand and DMSO for cycloaddition of carbon dioxide to propylene oxide

Cobalt complexes containing a salen-type pyridoxal ligand with pyridine were synthesized as a new Co(III) catalytic system for the cycloaddition of carbon dioxide. Two cobalt(III) complexes possessing a salen-type pyridoxyl ligand were synthesized by the reaction of pyridoxal ligands (pyr2en = (N,N′-bis(pyridoxylideneiminato)ethylene) and pyr2cy = (N,N′-bis(pyridoxylideneiminato)cyclohexane)) and Co(OAc)2 and characterized by various analytical methods, including infrared spectroscopy and high-resolution mass analysis. Single-crystal X-ray crystallography analysis confirmed that the cobalt pyr2en complex had a distorted octahedral structure: the tetradentate Schiff base ligand binds the cobalt metal in one plane, and the metal center adopts an octahedral geometry by the additional coordination of acetate and dimethyl sulfoxide. The synthesized complexes were used as catalysts in the cycloaddition of carbon dioxide (CO2) to propylene oxide. The catalysts showed high activity for cycloaddition between CO2 and epoxides, even at a low loading (0.5 mol%), in the presence of various cocatalysts.

Preparation ,Characterization and The Biological Activity Study of A new heterocyclic (Azo-Schiff base) ligand and Their Complexation with {Co,Ni,Cu,Zn(II)}Ions

A new tetra dentate Schiff base ligand has been synthesized from condensation of compound (1): [( 4 -((1-H-imidazol-2-yldiazenyl)-1,5-dimethyl-2-phenyl-1Hpyrazol-3(2H)-one)]with compound (2) thio semicarbazaide. The general formula of complexes are [M(L)]Cl2 Where. M= Co(II) ,Ni (II)and Cu(II)Zn(II) are reported. The geometry structures of ligand and the complexes were determined through Fourier-transform infrared spectroscopy (FT-IR), Mass spectra, X-ray diffraction analysis, Ultra violet-Visible(UV-Vis), Proton nuclear magnetic resonance(1H NMR) spectral studies, magnetic moment measurement, elemental analysis, and molar conductance. These studies revealed square planar geometries for Ni(II)and Co(II) and Cu(II)complexes, except the Zn(II) complex was a tetrahedral geometry around the central metal ion. Complex formation studies via molar ratio and continuous variation methods were consisted to those found in the solid complexes with a ratio of (M:L) as (1:1) . Stability constant of complexes were calculated by spectrophotometric methods. Hyper Chem-8 program has been used to predict geometries structures of compounds in gas phase. The heat of formation (∆Hf) and binding energy (∆E b) at 298 K for the metal complexes were calculated by PM3 method. Biological activity studies of the ligand and their metal complexes against several organisms, bacteria Gram positive G(+ve)staphylococcus aureus and bacteria Gram negative G(- ve)Escherichia coli, klebsiella pneumonic, In addition to fungi like Aspergillus Niger, Rhizoclonia bataicola and Aspergillus flavus , are reported. Compounds exhibited the high activity on the growth of all types microorganisms in this study. This may be attributed to the impact of both the chelate effect of Schiff bases ligand and the role of the metal in these complexes.

Stöber synthesis of salen-formaldehyde resin polymer- and carbon spheres with high nitrogen content and application of the corresponding Mn-containing carbon spheres as efficient electrocatalysts for the oxygen reduction reaction.

Salen-formaldehyde (SF) resin polymer spheres were synthesized by the Stöber method from 4,4′-dihydroxysalen (N,N′-bis-(4-hydroxysalicylidene)-ethylenediamine; a tetradentate N2O2 Schiff base ligand) and formaldehyde. The salen precursor was prepared by condensation of ethylenediamine with 2,4-dihydroxybenzaldehyde in methanol. The SF resin colloidal spheres were also prepared by using Pluronic F127 and ammonia as a porogenic agent and catalyst, respectively (SF-P). In addition, corresponding Mn(ii)-coordinated polymer spheres of the SF-P were synthesized (SF-P-Mn(ii)). Corresponding monodispersed carbon spheres of all of the abovementioned samples were also obtained by pyrolysis technique. All of the products were characterized with conventional microscopic and spectroscopic techniques, as well as other physical methods such as BET analysis. It was found that carbonization of the SF resin spheres results in carbon spheres with specific surface areas in the range of 499–528 m2 g−1 and average pore sizes in the range of 2.58–3.08 nm. Nitrogen content of the SF-MWHT (obtained hydrothermally in a methanol/water mixture), and SF-P-C@Mn (obtained from carbonization of SF-P-Mn(ii)) samples were as high as 27.5 wt% and 35.02 wt%, respectively. Finally, a glassy carbon electrode (GCE) modified with SF-P-C@Mn (SF-P-C@Mn/GCE) was prepared and its electrocatalytic activity was evaluated for oxygen reduction reaction (ORR) by linear sweep voltammetry (LSV). The LSV results showed that the SF-P-C@Mn/GCE has a higher current density and a lower negative potential in the ORR compared to GCE.

Synthesis and Crystal Structure of [Benzyl N'-[[2-(hydroxy-kO)phenyl]ethylene]-N-[[2-(hydroxy-kO)phenyl]methylene]-carbamohydrazonothioato-kN,kN']-ethanol-dioxido-uranium

The uranyl compound UO2(L')EtOH (L' = benzyl N-(2-(oxidanyl)benzylidene)-N'-((2-(1-oxidanyl)phenyl)ethylidene) carbamohydrazonothioate) was synthesized and its molecular and crystal structure was determined by X-ray diffraction. The compound crystallizes in the triclinic sp. gr. P$$\bar {1}$$, Z = 2. The coordination geometry about the uranium atom is distorted pentagonal bipyramidal consisting of a UO2O4N2 polyhedron where the oxido ligands occupy axial positions with a symmetric linear structure (O=U=O angle = 179.11(12)°). The pentagonal plane (N2O3) is formed by the dinegative, tetradentate Schiff base ligand (N2O2) and the oxygen atom of the coordinated alcohol ligand. In the complex, the ligand adopts a propeller-like conformation.

Synthesis, structure and DFT study of novel Ga(III) complexes containing a tetradentate ligand

Abstract The synthesis, structure and density functional theory (DFT) calculations of two novel Ga(III) complexes, the first containing a tetradentate Schiff base ligand (L1) and the second containing a tetradentate carboxamide ligand (L2), are presented. The complexes are isolated as octahedral complexes with two water molecules attached to the axial positions. Both experimental and DFT calculations show that when [Ga(L1)(H2O)2].NO3 is dissolved in dimethyl sulfoxide (DMSO), spontaneous substitution of axial water groups by DMSO occur to form [Ga(L1)(DMSO)2].NO3.

Crystal structure, spectroscopic studies, DFT calculations, cyclic voltammetry and biological activity of a copper (II) Schiff base complex

Abstract Herein we describe the chemical synthesis of a novel tetradentate Schiff base ligand (H2L), bridged with a pyridine, and its corresponding mononuclear copper complex (Cu(II)L). H2L, derived from the condensation of 2,3-diaminopyridine and 5-bromosalicylaldehyde, and Cu(II)L were structurally confirmed by routine spectral techniques, UV–Vis, FT-IR, 1H NMR, MS and elemental analysis. Single crystal X-ray diffraction analysis of Cu(II)L complex showed a monoclinic system with P21/C space group and Z = 4 molecules per unit cell. The characterization data of the complex revealed strong coordination via azomethine nitrogen (N) and bromo-phenolate oxygen (O). Moreover, the experimental parameters were found in line with the theoretical parameters. The conductivity measurement showed a non-electrolytic nature of the complex and the electrochemical behavior exhibits two quasi reversible redox processes. In-vitro antimicrobial studies on the synthesized compounds revealed a significant activity of the complex on some bacteria strains than the free ligand. DFT calculations were fully optimized using B3LYP and confirmed practical electrochemical and antibacterial results.

Solid-State Nonlinear Optical Properties of Mononuclear Copper(II) Complexes with Chiral Tridentate and Tetradentate Schiff Base Ligands.

Salen-type metal complexes have been actively studied for their nonlinear optical (NLO) properties, and push-pull compounds with charge asymmetry generated by electron releasing and withdrawing groups have shown promising results. As a continuation of our research in this field and aiming at solid-state features, herein we report on the synthesis of mononuclear copper(II) derivatives bearing either tridentate N2O Schiff bases L(a−c)− and pyridine as the forth ancillary ligand, [Cu(La−c)(py)](ClO4) (1a–c), or unsymmetrically-substituted push-pull tetradentate N2O2 Schiff base ligands, [Cu(5-A-5′-D-saldpen/chxn)] (2a–c), both derived from 5-substituted salicylaldehydes (sal) and the diamines (1R,2R)-1,2-diphenylethanediamine (dpen) and (1S,2S)-1,2-diaminocyclohexane (chxn). All compounds were characterized through elemental analysis, infrared and UV/visible spectroscopies, and mass spectrometry in order to guarantee their purity and assess their charge transfer properties. The structures of 1a–c were determined via single-crystal X-ray diffraction studies. The geometries of cations of 1a–c and of molecules 2a–c were optimized through DFT calculations. The solid-state NLO behavior was measured by the Kurtz–Perry powder technique @1.907 µm. All chiral derivatives possess non-zero quadratic electric susceptibility (χ(2)) and an efficiency of about 0.15–0.45 times that of standard urea.

Copper(II) Coordination Complex Constructed from Halogenated Tetradentate Schiff Base Ligand: Synthesis, Crystal Structure, and Hirshfeld Surface Analysis

Copper complex [Cu-3Br-salen]] (3-Br-salen = N,N'-bis(3-bromosalicylidene)ethylene-1,2-diamine) is synthesized as a part of the research work of exploring the relationship between the constitution of Schiff-base ligands and the complex structures. The single-crystal X-ray diffraction analysis indicates that the title compound crystallizes in the monoclinic system, sp. gr. Pbca, Z = 8. IntermolecIular hydrogen bonds and the π···π stacking interactions form 2D networks between which there is only van der Waals interaction. Besides, Hirshfeld surface analysis was used to further study the intermolecular interactions of the complexes.

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.