Transition Metal Schiff Base Complexes Research Articles

Biocompatibility assessment of chemically modified GONRs with hemoglobin and histopathological studies for its toxicity evaluation.

Transition metal-Schiff base complexes are found to be important for biomedical applications but have demerits of being homogeneous complexes, thus their synthesis on the surface of graphene oxide nanoribbons (GONRs), materials of specific interest, can be beneficial for preparing advanced graphene-based materials for biomedical applications. Of foremost importance is their safety and biocompatibility with biological systems. In this study, a transition metal-Schiff base complex has been synthesized on the surface of a GONR (Ni-S-GNR) using 3-aminopropyltriethoxysilane and pyridine-2-carbaldehyde and complexing nickel. This Ni-S-GNR was characterized well by various physicochemical techniques. The evaluation of biocompatibility of Ni-S-GNR with hemoglobin confirmed binding interactions and influence on the native structure of hemoglobin. It was found that there was alteration in the secondary and tertiary structures of hemoglobin. In addition, histopathological studies on the liver and kidney cells of rats revealed non-toxicity of Ni-S-GNR towards these cells. Overall, Ni-S-GNR was found to be compatible with protein as the native structure was not destroyed and was non-toxic to cells.

Transition metal Schiff base complexes supported on layered double hydroxide: synthesis, characterization and catalytic activity for the oxidation of toluene

The catalytic oxidation of toluene was studied over Mn(III) and Fe(III) Schiff base complexes supported layered double hydroxide catalysts. The supported catalysts were synthesized by intercalation method and abbreviated as LDH-[NAPABA-M], {where M = Mn(III) and Fe(III)}. The obtained material was characterized by various physical techniques such as ICP-AES, EDX, XRD, FTIR, SEM, TEM, BET surface area, EPR, and TGA. The liquid-phase catalytic oxidation of toluene was studied using LDH-[NAPABA-M]/TBHP system. A maximum conversion of toluene (55.3%) and selectivity of benzaldehyde (86.1%) was observed with LDH-[NAPABA-Mn(Cl)]/TBHP system, when the reaction is carried out at toluene to tert-butylhydroperoxide (TBHP) molar ratio 1:3, temperature 373 K, and catalyst amount, 100 mg. The catalyst, LDH-[NAPABA-Mn(Cl)] gave excellent; conversion of toluene and selectivity of benzaldehyde in comparison to LDH-[NAPABA-Fe(Cl)] catalyst. The catalyst, LDH-[NAPABA-Mn(Cl)] showed good stability and reusability up to five cycles without significant loss of catalytic activity.

Fluorimetric Detection of Phosphates in Water Using a Disassembly Approach: A Comparison of FeIII‐, ZnII‐, MnII‐ and MnIII‐salen Complexes

Details of the reaction sequence used for the fluorimetric detection of phosphates by disassembly of transition metal Schiff base complexes were investigated for [FeIII(salen)(H2O)]+, [ZnII(salen)], [MnII(salen)(H2O)2], and [MnIII(salen)(H2O)]+. The reactivity of these compounds towards phosphorus oxoanions of differing charge, number of donor atoms and steric hindrance was detected by UV/Vis and fluorescence spectroscopy in both aprotic organic and aqueous media. Selectivity of [FeIII(salen)(H2O)]+ towards pyrophosphate over all other tested phosphorus‐containing analytes was strongly supported. [ZnII(salen)] showed a faster reactivity but was much less selective. In contrast, [MnIII(salen)(H2O)]+ proved to be more stable than the iron complex but generally showed little reactivity towards phosphorus oxoanions. The influence of the charge of the central atom was investigated using the MnII analogue [MnII(salen)(H2O)2]. As expected, the reduced charge resulted in a reactivity comparable to the ZnII complex in organic solution but lead to hydrolysis of the complex in water. Finally, the reaction products of [FeIII(salen)(H2O)]+ with phosphates were characterized by IR spectroscopy and mass spectrometry, providing further insights into the reaction mechanism of the disassembly process.

A review of Titanium, Vanadium and Chromium transition metal Schiff base complexes with biological and catalytic activities

Schiff bases are compounds obtained from the condensation reaction of a primary amine and aldehyde or ketone They can be coordinated with metals especially the transition metals to form Schiff base complexes The objective of this work is to review the synthesis biological as well as catalytic activities of both Schiff base ligands and their transition metal complexes of titanium vanadium as well as chromium The methodology used for looking for the references were through the internet Biological activities that were considered in this review were mainly those of antibacterial and antifungal For the antibacterial both gram positive and gram negative strain were considered The results obtained from the study indicated that the Schiff base complexes Schiff bases as well as metal ions for the metals titanium vanadium and chromium were used by different researchers to investigate antimicrobial activities against bacteria fungi as well as anti tumour activity against breast cancer The antimicrobial literature studies showed that the metal ions were having lower inhibition capacity than the ligands but the complexes showed the highest inhibition capacity against the microbial The use of Mono and dioxide complexes showed anticancer activity against MCF breast cancer cells The cis Dioxido vanadium V complexes were also investigated for catalytic activity on the oxidation of cyclohexane and gave conversion of and selectivity of up to The paper is divided into five sections which include introduction methodology used in looking for references results and discussion acknowledgements and references The results obtained from the review show that the Schiff base complexes were more effective when screened as anti microbial compounds than their ligands The complexes also showed effectiveness when screened for their catalytic activity on organic chemistry reactions

Transition Metal Schiff Base Complexes Synthesis, Spectral Examination and used as a Catalyst in the Oxidation of Alcohols and C-C Coupling Reactions

In this correspondence, it reveals the formation of Co (II) and Cu (II) complexes consists of a Schiff base ligand having the four donar destinations 2NO. Co(II) and Cu(II) complexes were made ready by the response of 1:1 proportion of the MCl2 .6H2O (M = Co/Cu) with a Schiff base ligand prepared by the response of 2-hydroxynaphthaldehyde with orthophenylene diamine in ethanolic medium having the stoichimetric proportion of 2:1. The purged and arranged complexes were analytically explored. Catalytic efficacy was assessed for oxidation of alcohols and C-C coupling responses.

Supported transition metal catalysts of Cu(II), Mn(II) and Co(II): synthesis, characterization, and catalytic behavior

A variety of heterogeneous transition metal Schiff base complexes have been prepared by their intercalation in layered double hydroxide, abbreviated as LDH-[SALABA-M] {where M is Cu, Mn and Co}. The synthesized catalysts are characterized by various analytical techniques like X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, inductive coupled plasma-atomic emission spectroscopy, thermogravimetric analysis, Brunauer–Emmett–Teller surface area etc. The aforesaid catalysts are employed for the oxidation of cyclohexene. Effect of various metals, substrate to oxidant molar ratio, temperature, and catalyst amount etc. have been studied so as to derive optimum conditions for obtaining maximum conversion. Tert-butyl hydroperoxide has been used as an oxidant in acetonitrile solvent. The oxidation products obtained are 2-cyclohexene-1-ol and 2-cyclohexene-1-one. The catalyst, LDH-[SALABA-Cu(II)] is recycled ten times in consecutive runs. Additionally, mechanism of reaction is found out using quenching study.

Installation of internal electric fields by non-redox active cations in transition metal complexes.

Local electric fields contribute to the high selectivity and catalytic activity in enzyme active sites and confined reaction centers in zeolites by modifying the relative energy of transition states, intermediates and/or products. Proximal charged functionalities can generate equivalent internal electric fields in molecular systems but the magnitude of their effect and impact on electronic structure has been minimally explored. To generate quantitative insight into installing internal fields in synthetic systems, we report an experimental and computational study using transition metal (M1) Schiff base complexes functionalized with a crown ether unit containing a mono- or dicationic alkali or alkaline earth metal ion (M2). The synthesis and characterization of the complexes M1 = Ni(ii) and M2 = Na+ or Ba2+ are reported. The electronic absorption spectra and density functional theory (DFT) calculations establish that the cations generate a robust electric field at the metal, which stabilizes the Ni-based molecular orbitals without significantly changing their relative energies. The stabilization is also reflected in the experimental Ni(ii/i) reduction potentials, which are shifted 0.12 V and 0.34 V positive for M2 = Na+ and Ba2+, respectively, compared to a complex lacking a proximal cation. To compare with the cationic Ni complexes, we also synthesized a series of Ni(salen) complexes modified in the 5' position with electron-donating and -withdrawing functionalities (-CF3, -Cl, -H, -tBu, and -OCH3). Data from this series of compounds provides further evidence that the reduction potential shifts observed in the cationic complexes are not due to inductive ligand effects. DFT studies were also performed on the previously reported monocationic and dicatonic Fe(ii)(CH3CN) and Fe(iii)Cl analogues of this system to analyze the impact of an anionic chloride on the electrostatic potential and electronic structure of the Fe site.

Nanographene Sheet Immobilized Transition Metal Complexes for C-C Coupling Reactions

Transition metal Schiff base complexes covalently immobilized on the surface of amino functionalized graphene sheet to catalyze C-C coupling reaction is reported. Graphene sheet which synthesized using mechanical exfoliation and then by differential oxidative reduction phenomenon of graphite. The schiff base ligand is prepared using aldehyde and amino groups containing compounds which further treated with metal salts to form metal complexes. The as-synthesized metal complexes was then incorporated into amino functionalized nanosheets which are characterized using different spectrochemical techniques. The catalytic investigation of the as-prepared catalyst were done by the cross coupling of aryl halides and aryl boronic acids to form biaryls as product in C-C cross coupling reaction. The yield of the products were high and selective which were analyzed using Gas chromatography technique. The advantage of this catalyst is high stability, recyclability easy recovery of catalyst, environmentally benign and mild reaction condition.

Synthesis and characterization of transition metal complexes with a Schiff base derived from cephalexin and 1,2–diaminobenzene. antibacterial activity

From the reaction of 1,2-diaminobenzene 1 with cephalexin 2 antibiotic a cephalexin–based Schiff base (HL) 3, was obtained and the transition metal Schiff base complexes were synthesized. The products were characterized by physical and spectral techniques, namely, UV–Vis, FT-IR, 1H-NMR, EPR, MALDI mass spectrometry, magnetic susceptibility, molar conductance, molecular modeling, together with elemental and thermal analysis. The general composition [M(L)(OAc)(H2O)2], M(II) = Mn2+ 4, Co2+ 5, Ni2+ 6, Cu2+ 7, Zn2+ 8, where L represents deprotonated tridentate NNO Schiff base, have been assigned to the adducts. Direct calcinations of the complexes 6 and 8 at 700 °C resulted high-quality metal oxide (MO) nanoparticles. Paper disc diffusion method was used to test the bactericidal activity of the synthesized products.

Antibacterial activity of transition metal complexes with a tridentate NNO amoxicillin derived Schiff base. Synthesis and characterization

From the reaction of amoxicillin (1) antibiotic with 2,6−diaminopyridine (2) an amoxicillin−based Schiff base (HL) (3) was obtained and its transition metal Schiff base complexes were synthesized. Spectroscopic and physicochemical techniques, namely, UV−Vis, FT−IR, 1H−NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility, molecular modelling, together with elemental and thermal analyses, were used to characterize the synthesized compounds. Spectral and magnetic data suggested an octahedral geometry for all the complexes and the general formulae [ML(H2O)3][PF6] (M(II) = Mn2+ (4), Co2+ (5), Ni2+ (6), Cu2+ (7), Zn2+ (8), was proposed for them, where L represents deprotonated tridentate NNO amoxycillin−derived Schiff base. All compounds were screened for antibacterial activity by using agar disc diffusion method. The zinc(II) complex exhibited promising bactericidal activity against E. coli and S. aureus.

Schiff base complex conjugates of bovine serum albumin as artificial metalloenzymes for eco-friendly enantioselective sulfoxidation.

Artificial metalloenzymes (BSA-ML) have been prepared by non-covalent insertion of transition metal Schiff-base complexes, ML (L = 2-hydroxynaphthalen-1-naphthaldehyde and 3,4-diaminobenzenesulfonic acid; M = Co, Mn, V, Fe, Cr), into bovine serum albumin (BSA) as the host protein and were characterized by UV-visible spectroscopy, ESI-TOF mass spectrometry and molecular docking studies. The catalytic activities of the BSA-ML in the selective oxidation of various prochiral sulfides in aqueous media, using H2O2 as oxidant, have been evaluated. During the optimization process, pH and the concentrations of catalyst and oxidant were found to have a remarkable influence on both yield and enantioselectivity. In certain cases, BSA-ML gave satisfactory results in the oxidation of organic sulfides to sulfoxides (up to 100% conversion, 100% chemoselectivity, 96% ee and 500 h−1 turnover frequency).

X-ray crystallography, electrochemistry, spectral and thermal analysis of some tetradentate schiff base complexes and formation constant measurements

ABSTRACTA series of new transition metal Schiff base complexes was synthesized via the reaction of H2L (N,N′-bis(naphthylidene)-2-aminobenzylamine) with the transition metals (Cu2+, Co2+, Ni2+, Zn2+ and Mn2+) and characterized by elemental analysis, 1HNMR, FT-IR, UV-Vis spectroscopy, thermogravimetric analysis(TG) and in selected cases by X-ray crystallography. Thermodynamics of complex formation, electrochemistry of the metal Schiff base complexes and kinetic aspects of thermal decomposition of the complexes were also studied. The obtained formation constants change according to the following trend due to the electronegativity and Jahn-Teller effects of the central transition metals: Cu > Co > Ni > Zn >Mn. Cyclic voltammogram of the complexes in acetonitrile was done to evaluate the redox behavior of the complexes. Electrochemistry of these complexes showed a redox reaction without any successive reactions. Furthermore, kinetic parameters which calculated by Coats–Redfern equation revealed a first-order kinetics of thermal decomposition in all stages.

RETRACTED ARTICLE: Schiff base transition metal complexes for Suzuki–Miyaura cross-coupling reaction

Schiff base ligand and its complex with iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) ions were synthesized using 4-aminoacetophenone and salicylaldehyde and characterized. FTIR spectrum shows that bidentate coordination of metal ions with ligand where O, N are electron donating sites of azomethine group. The geometry of the complexes was deduced from the calculated magnetic moment values and SCXRD analysis. All complexes were studied for their catalytic activity in Suzuki–Miyaura cross-coupling reaction with Cu–L complex showing excellent coupling yield among others. The catalytic activity data show promising results in coupling efficiency, employing cheap, abundant and green metals. Synopsis The transition metal Schiff base complexes synthesized and characterized by SCXRD, Mass spectrometry, TGA, UV–Vis and FTIR analysis. Magnetic susceptibility measurements were also examined to know the plausible geometry of the complex. The synthesized complexes were systematically investigated for Suzuki–Miyaura cross-coupling reactions and optimized to enhance the yield of the Suzuki reaction.

Co (II) Complexes with Schiff Base Ligands: Synthesis and EXAFS Study

Thesynthesis of transition metal Schiff base complexes of Co(II) are prepared by chemical root method. Obtained by the condensation of O-phenylenediamine, salicylaldehyde and isatin / 2-hydroxy- 1 Naphthaldehyde is presented. The complexes were characterized by Co- K- edge EXAFS measurements using the dispersive beam line at 2.5GeV energy of Indus-2 synchrotron radiation source RRCAT Indore. The recorded EXAFS data were analyzed using the computer software Athena for determine the nearest neighboring distances (bond lengths) of these complexes with conventional methods and were compared with Fourier transform (FT) analysis.

Exafs and comparative studies of copper (II) complexes

The present paper deals with the synthesis of transition metal Schiff base complexes of copper by chemical root method. The synthesized metal complexes were characterized by Extended X-ray absorption fine structure (EXAFS) is a technique that has been used for determining the metal ligand bond length using conventional X-ray source and also by EXAFS analysis using IFEFFIT programming. Bond lengths determined from these data analysis methods are compared with the bond lengths obtained from LSS, Levy's and Lytle's methods. Bond lengths of the complexes are in good agreement obtained by theoretical and experimental method.

EXAFS study of copper thiosemicarbazide complexes

The present paper deals with the synthesis of transition metal Schiff base complexes of copper by chemical root method. The synthesized metal complexes have been studied by extended X-ray absorption fine structure (EXAFS) technique. The metal ligand bond length have been determined using LSS, Levy's and Lytle's methods. Bond-lengths have also been determined from the Fourier transform of the EXAFS data. Bond lengths determined from these methods are comparable to each other.

A Theoretical Investigation into the Luminescent Properties of d8‐Transition‐Metal Complexes with Tetradentate Schiff Base Ligands

A theoretical investigation on the luminescence efficiency of a series of d(8) transition-metal Schiff base complexes was undertaken. The aim was to understand the different photophysics of [M-salen](n) complexes (salen = N,N'-bis(salicylidene)ethylenediamine; M = Pt, Pd (n = 0); Au (n = +1)) in acetonitrile solutions at room temperature: [Pt-salen] is phosphorescent and [Au-salen](+) is fluorescent, but [Pd-salen] is nonemissive. Based on the calculation results, it was proposed that incorporation of electron-withdrawing groups at the 4-position of the Schiff base ligand should widen the (3)MLCT-(3)MC gap (MLCT = metal-to-ligand charge transfer and MC = metal centered, that is, the dd excited state); thus permitting phosphorescence of the corresponding Pd(II) Schiff base complex. Although it is experimentally proven that [Pd-salph-4E] (salph = N,N'-bis(salicylidene)-1,2-phenylenediamine; 4E means an electron-withdrawing substituent at the 4-position of the salicylidene) displays triplet emission, its quantum yield is low at room temperature. The corresponding Pt(II) Schiff base complex, [Pt-salph-4E], is also much less emissive than the unsubstituted analogue, [Pt-salph]. Thus, a detailed theoretical analysis of how the substituent and central metal affected the photophysics of [M-salph-X] (X is a substituent on the salph ligand, M = Pt or Pd) was performed. Temperature effects were also investigated. The simple energy gap law underestimated the nonradiative decay rates and was insufficient to account for the temperature dependence of the nonradiative decay rates of the complexes studied herein. On the other hand, the present analysis demonstrates that inclusions of low-frequency modes and the associated frequency shifts are decisive in providing better quantitative estimates of the nonradiative decay rates and the experimentally observed temperature effects. Moreover, spin-orbit coupling, which is often considered only in the context of radiative decay rate, has a significant role in determining the nonradiative rate as well.

Analgesic and Anti-Inflammatory Activities of some Transition Metal Schiff Base Complexes

Analgesic and anti-inflammatory activities of four transition metal complexes of a Schiff base derived from salicylaldehyde and glycine, viz. [N-salicylideneglycinato diaqua cobalt(II) dimer] (SGCo)2, [N-salicylideneglycinato-di-aqua-nickel(ll)dimer] (SGN)2, [N-salicylideneglycinato-aqua-copper(II)] (SGC) and [N-salicylideneglycinato diaqua zinc(II) dimer] (SGZ)2 were studied in swiss albino mice. 10 mg/kg (p.o) dose for each compound were selected throughout the research work. The analgesic activity was determined by acetic acid induced writhing and tail immersion methods. All such data were compared with standard drugs at the dose of 10 mg/kg (p.o. The anti-inflammatory activity of the test compounds was determined by the carragenan induced mice paw edema inhibition method.). Analgesic and anti-inflammatory activities of the test compounds at 10 mg/kg (p.o.) were quite comparable to those of standard drugs at 10 mg/kg (p.o.). All these compounds can be considered as potent analgesic and anti-inflammatory agents.

Analgesic and Anti-Inflammatory Activities of some Transition Metal Schiff Base Complexes

Analgesic and anti-inflammatory activities of four transition metal complexes of a Schiff base derived from salicylaldehyde and glycine, viz. [N-salicylideneglycinato diaqua cobalt(II) dimer] (SGCo)2, [N-salicylideneglycinato-di-aqua-nickel(ll)dimer] (SGN)2, [N-salicylideneglycinato-aqua-copper(II)] (SGC) and [N-salicylideneglycinato diaqua zinc(II) dimer] (SGZ)2 were studied in swiss albino mice. 10 mg/kg (p.o) dose for each compound were selected throughout the research work. The analgesic activity was determined by acetic acid induced writhing and tail immersion methods. All such data were compared with standard drugs at the dose of 10 mg/kg (p.o. The anti-inflammatory activity of the test compounds was determined by the carragenan induced mice paw edema inhibition method.). Analgesic and anti-inflammatory activities of the test compounds at 10 mg/kg (p.o.) were quite comparable to those of standard drugs at 10 mg/kg (p.o.). All these compounds can be considered as potent analgesic and anti-inflammatory agents.

Immobilization of transition metal (Fe2+, Co2+, VO2+ or Cu2+) Schiff base complexes onto graphene oxide as efficient and recyclable catalysts for epoxidation of styrene

Transition metal (Fe2+, Co2+, VO2+ or Cu2+) Schiff base complexes were immobilized onto graphene oxide previously functionalized with 3-aminopropyltriethoxysilane (3-APTES). X-ray diffraction (XRD), IR spectroscopy, thermal gravimetric analyses (TGA) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) confirmed the successful incorporation of the metal Schiff base onto the graphene oxide. N2 adsorption–desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the intact structure of the graphene oxide. Catalytic results showed that the immobilized copper(II) Schiff base complex catalyst was more active than the immobilized iron(II), cobalt(II) and oxovanadium(IV) complexes in the epooxidation of styrene. Above 94% styrene conversion and excellent ∼99% selectivity to the epoxide could be achieved over the copper(II) Schiff base heterogeneous catalyst in the epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as oxidant after 7 h reaction. The recycling experiment results indicated that the catalyst could maintain very high styrene conversion (>93%) and epoxide selectivity (>99%) even after being used for four cycles.