Active Transition Metal Complexes Research Articles

تحضير ، تشخيص دراسة التحلل الحراري فعالية مضادات الاكسدة لمعقدات العناصر الانتقالية مع ليكاند صبغة الازو

تم إجراء تفاعل ديازوتيزيشن بين 1- (6,4,2-ثلاثي هيدروكسي-فينيل) -إيثانون وأملاح ديازونيوم مما أدى إلى تكوين ليكاند 4- (3-أسيتيل -2،4،6-ثلاثي هيدروكسي-فينيل ازو) -N- (5-ميثيل-إيزوكسازول-3-يل) -بنزين سلفوناميد ، وهذا بدوره يتفاعل مع أيونات المعادن التالية (+V4، +Cr3، +Mn2 و +Cu2) مكونة معقدات مستقرة ثمانية السطوح لكل من الكروم والمنغنيز والنحاس و هرمي مربع القاعدة لـلفناديوم الرباعي .تم اكتشاف إنشاء مثل هذه المعقدات من خلال استخدام الوسائل الطيفية التي تنطوي على الأشعة فوق البنفسجية التي أثبتت الأشكال الهندسية التي تم الحصول عليها ، وأثبت IR تكوين مجموعة الآزو والتنسيق مع أيون المعدن من خلالها. أثبتت دراسات الانحلال الحراري (TGA & DSC) تنسيق بقايا الماء مع أيونات المعادن داخل مجال التناسق وكذلك ذرات الكلور. علاوة على ذلك ، التحليل الجزئي للعنصر و AAS الذي أعطى النتيجة المقابلة مع نتيجة العد النظري. (H &13C-NMR1) والكميات المغناطيسية يمكن أن تشير أيضًا إلى تكوين ليكاند H3L وحدوث التنسيق. تم حساب الثوابت الديناميكية الحرارية (H∆, S∆, G∆). سيتم استخدام طريقة الكسح الجذري DPPH لتقييم الأنشطة المضادة للأكسدة للمركبات التي أظهرت قدرتها المضادة للأكسدة على اخماد الجذور الحرة.

A brief review on the antimicrobial activity of transition metal complexes with N,O donor chelating ligand

Activities of microorganisms can immensely influence our health. Our present environment is highly dominated by microorganisms and our future will also be highly impacted by their activities. We need to control microbial populations in order to prevent transmission of infections and disease, and to do that we require antimicrobial medicines. But unfortunately their drug resistance is becoming a major cause of morbidity and mortality at the present time. For this reason, we have to focus on design and development of novel antimicrobial drugs in order to control infections and diseases. Metal complexes usually contain a variety of structural and electronic features which can be exploited in designing of drugs. The metal ion and its oxidation state, as well as coordination geometries and coordination numbers can be varied. These properties allow the fine-tuning of chemical reactivity, including the rates of ligand exchange, the strength of metal–ligand bonds, metal- and ligand- based redox potentials, ligand conformations, and outer-sphere interactions. These review works depict the current studies on the antimicrobial activities of transition metal complexes with N, O donor chelating agent.

Paramagnetic Relaxation Agents for Enhancing Temporal Resolution and Sensitivity in Multinuclear FlowNMR Spectroscopy.

Sensitivity in FlowNMR spectroscopy for reaction monitoring often suffers from low levels of pre-magnetisation due to limited residence times of the sample in the magnetic field. While this in-flow effect is tolerable for high sensitivity nuclei such as 1 H and 19 F, it significantly reduces the signal-to-noise ratio in 31 P and 13 C spectra, making FlowNMR impractical for low sensititvity nuclei at low concentrations. Paramagnetic relaxation agents (PRAs), which enhance polarisation and spin-lattice relaxation, could eliminate the adverse in-flow effect and improve the signal-to-noise ratio. Herein, [Co(acac)3 ], [Mn(acac)3 ], [Fe(acac)3 ], [Cr(acac)3 ], [Ni(acac)2 ]3, [Gd(tmhd)3 ] and [Cr(tmhd)3 ] are investigated for their effectiveness in improving signal intensity per unit time in FlowNMR applications under the additional constraint of chemical inertness towards catalytically active transition metal complexes. High-spin Cr(III) acetylacetonates emerged as the most effective compounds, successfully reducing 31 P T1 values four- to five-fold at PRA concentrations as low as 10 mM without causing adverse line broadening. Whereas [Cr(acac)3 ] showed signs of chemical reactivity with a mixture of triphenylphosphine, triphenylphosphine oxide and triphenylphosphate over the course of several hours at 80° C, the bulkier [Cr(tmhd)3 ] was stable and equally effective as a PRA under these conditions. Compatibility with a range of representative transition metal complexes often used in homogeneous catalysis has been investigated, and application of [Cr(tmhd)3 ] in significantly improving 1 H and 31 P{1 H} FlowNMR data quality in a Rh-catalysed hydroformylation reaction has been demonstrated. With the PRA added, 13 C relaxation times were reduced more than six-fold, allowing quantitative reaction monitoring of substrate consumption and product formation by 13 C{1 H} FlowNMR spectroscopy at natural abundance.

Synthesis and Characterization of some biologically active transition metal complexes for a ligand derived from dimedone with mixed ligands.

The aim of the work is synthesis and characterization of bidentate ligand
 [3-(3-acetylphenylamino)-5,5-dimethylcyclohex-3-enone][HL], from the
 reaction of dimedone with 3-amino acetophenone to produce the ligand
 [HL], the reaction was carried out in dry benzene as a solvent under reflux.
 The prepared ligand [HL] was characterized by FT-IR, UV-Vis
 spectroscopy, 'H, 8C-NMR spectra, Mass spectra, (C.H.N) and melting
 point. The mixed ligand complexes were prepared from ligand [HL] was
 used as a primary ligand while 8-hydroxy quinoline [HQ] was used as a
 secondary ligand with metal ion M(IT).Where M(IT) = (Mn ,Co ,Ni ,Cu ,Zn
 ,Cd and Pd) at reflux ,using ethanol as a solvent, KOH as a base.
 Complexes of the composition [M(L)(Q)] with (1:1:1) molar ratio were
 prepared . All the complexes were characterized by spectroscopic methods
 (FT-IR, UV-Vis spectroscopy) along with elemental analysis (A.A),
 chloride content and melting point measurements were carried out, together
 with conductivity and magnetic susceptibility. These measurements showed
 tetrahedral geometry around (Mn", Col, Ni, Cu", Zn! and Cd") ions and
 square planner around (Pd") ion. The biological activity of the ligands
 [HL],[HQ] ] and complexes (MLQ): were studied using inhibition method.

Pharmacological aspects of Co(II), Ni(II) and Cu(II) schiff base complexes: An insight

Schiff bases are versatile chemical compounds that are frequently utilized and manufactured by reacting various amines with carbonyl compounds (aldehydes/ketones), resulting in the formation of the azomethine/imine (–CN–) group by condensation reaction. Medical science is driven to generate novel drugs with revolutionary bioactivities and functionalities to cure diseases that are rapidly evolving. Schiff base (SB) is a dynamic pharmacophore that, through chelation, can create complexes with metals of various oxidation states. SB metal complexes have already been recognized as an effective branch of investigation in coordination science. In the recent years, scientists have paid close attention to SBs and the metal complexes owing to versatile potential in the pharmaceutics sector, such as antifungal, antibacterial, antiviral and antimalarial, anti-HIV, anti-cancer, anti-tuberculosis, and many others. These compounds have also been identified as potent oxidants, with applications in sensing and nanotechnology. The ligand environment, metal ion complexation, and lipophilic nature have an impact on the biological activity of transition metal complexes. SB metal complexes are the attractive targets for the development of broad-spectrum medicines due to their combination of pharmacological properties. The review focuses on the synthesis, spectroscopic characterization and in-vitro biomedical applications (antimicrobial, anticancer, antitumor, DNA binding and cleavage, antioxidant) of SBs as well as their Co(II), Ni(II) and Cu(II) transition metal complexes.

A metal-organic framework-supported dinuclear iron catalyst for hydroboration of carbonyl compounds.

Preparation of catalytically active dinuclear transition metal complexes with an open coordination sphere is a challenging task because the metal sites tend to be "saturated" with excess donor atoms around during synthesis. By isolating the binding scaffolds with the metal-organic framework (MOF) skeleton and installing metal sites through post-synthetic modification, we succeed in constructing a MOF-supported metal catalyst, namely FICN-7-Fe2, with dinuclear Fe2 sites. FICN-7-Fe2 effectively catalyses the hydroboration of a broad range of ketone, aldehyde, and imine substrates with a low loading of 0.05 mol%. Remarkably, kinetic measurements showed that FICN-7-Fe2 is 15 times more active than its mononuclear counterpart FICN-7-Fe1, indicating that cooperative substrate activation on the two Fe centres significantly enhances the catalysis.

DESIGN, SYNTHESIS AND BIOLOGICAL PROPERTIES OF TRANSITION METAL COMPLEXES OF SCHIFF BASE LIGAND DERIVED FROM PYRIDINE DERIVATIVES

Novel classes of heterocyclic Schiff base ligand were prepared from the condensation of 2-methoxy benzaldehyde and 2-amino 4-methyl pyridine in absolute ethanol in presence of catalytic amount of dilute HCl. The resulted novel class ofheterocyclic ligand was treated with metal salt or acetate results in the formation of Fe (III), Co (III), Ni (II) & Cu (II)complexes. All newly synthesized resulted ligand its metal complexes were characterized by elemental analysis and FTIR,Magnetic susceptibility, Antimicrobial, Antioxidant, ESR spectrum for Copper complex in DMF solvent recorded atroom temperature. The Electronic spectra and magnetic susceptibility measurements indicates that square planer andoctahedral geometry of these complexes also suggest their structure in which (N, O) group acts as bidentate ligand. Thethermal stability, decomposition behavior has been investigated by using thermo gravimetric analysis at heating rate 10°Cper minute with nitrogen atmosphere and their and kinetic parameter was also calculated by using Freeman Carrollmethod. Screening results of antimicrobial, antioxidant activity of transition metal complexes shows good antibacterialand antifungal activity and excellent antioxidant activity.

Cu(II) Complexes with Proline-Derived Schiff Base Ligand: Chemical Resolution of N,C-Unprotected α-Amino Acids and Their Antibacterial Activity

An operationally simple and convenient resolution method via Cu(II) complexes was reported, efficiently providing valuable enantiopure N,C-unprotected α-amino acids. This protocol features synthetically attractive yields and a stereochemical outcome, using a recyclable Schiff base ligand and inexpensive easily accessible metal copper salts. These novel Cu(II) complexes can be obtained in an enantiopure state by means of column chromatography or recrystallization. Furthermore, all the Cu(II) complexes were evaluated for their antibacterial activities. Among them, complexes (S,2S)-3a, (S,2S)-3g, and (S,2S)-3o showed significant antibacterial activities against Staphylococcus aureus Mu50. Further biological evaluation indicated that they were effective against most of Gram-positive bacteria. It is the first study on the biological activities of transition metal complexes with this type of proline-derived Schiff base ligand.

Synthesis, spectral analysis, DFT-assisted studies, in vitro antioxidant and antimicrobial activity of transition metal complexes of hydrazone ligands derived from 4-nitrocinnemaldehyde

Synthesis, spectral analysis, DFT-assisted studies, in vitro antioxidant and antimicrobial activity of transition metal complexes of hydrazone ligands derived from 4-nitrocinnemaldehyde

Rhenium-guanidine complex as photosensitizer: trigger HeLa cell apoptosis through death receptor-mediated, mitochondria-mediated, and cell cycle arrest pathways.

The growing evidence over the past few decades has indicated that the photodynamic antitumor activity of transition metal complexes, and Re(I) compounds are potential candidates for photodynamic therapy. This study reports the synthesis, characterization, and anti-tumor activity of three new Re(I)-guadinium complexes. Cytotoxicity tests reveal that complex Re1 increased cytotoxicity by 145-fold from IC50 >180μM in the dark to 1.3± 0.7μM following 10 min of light irradiation (425nm) in HeLa cells. Further, the mechanism by which Re1 induces apoptosis in the presence or absence of light irradiation was investigated, and results indicate that cell death was caused through different pathways. Upon irradiation, Re1 first accumulates on the cell membrane and interacts with death receptors to activate the extrinsic death receptor-mediated signaling pathway, and then is transported into the cell cytoplasm. Most of the intracellular Re1 locates within mitochondria, improving the reactive oxygen species level, and decreasing mitochondrial membrane potential and ATP levels, and inducing the activation of caspase-9 and, thus, apoptosis. Subsequently, the residual Re1 can translocate into the cell nucleus, and activates the p53 pathway, causing cell cycle arrest and eventually cell death.

AIE or AIE(P)E-active transition metal complexes for highly sensitive detection of nitroaromatic explosives

Nitroaromatic compounds (NACs) that are components of explosives have become seriously endanger human health, environmental cleaning, national homeland security, etc. The development of appropriate probes for the detection of NACs with desired easy operability, rapid response, reusability and high sensitivity and selectivity advantages has remained a great challenge. Over the past few years, great efforts have been made toward the development of advanced functional materials based on aggregation-induced emission or aggregation induced emission (phosphorescence) enhancement (AIE or AIE(P)E)-active transition metal complexes(AIEgens)and their remarkable achievements in the detection of NACs due to their high quantum yield and tunable photophysical properties. In this review, a brief description of luminescent AIEgens is presented, accompanied by a study on the Ir(III), Re(I) and Pt(II)-based AIEgens as sensing materials for nitroexplosives detection. Then, the trends and challenges of AIE or AIE(P)E-active transition metal complexes for the sensitive and selective detection of nitroaromatic explosives are also discussed.

Mechanochemical Synthesis of Biologically Active Transition Metal Complexes of 1H-4,4,6-Trimethyl-3,4-dihydropyrimidine-2-thione

A new series of metal complexes using 1H-4,4,6-trimethyl-3,4-dihydro-2-pyrimidinethione (HTMPT) ligand were synthesized mechanochemically and also evaluated for antibacterial and DNA photocleavage potential. Complexes of 1H-4,4,6-trimethyl-3,4-dihydro-2-pyrimidinethione (HTMPT) [M(tmpt)2(H2O)n] (M = Cu2+, Mn2+, Ni2+, Co2+; n = 2 and M = Zn2+, Cd2+, Pd2+; n = 0) were synthesized in 1:2 metal ligand ratio. All the metal complexes were characterized by 1H NMR, FTIR, UV-vis, ESI-mass spectrometry, molar conductivity, magnetic and thermal measurements. 1H NMR and IR results showed that the coordination occurs via N and S forming four-membered cyclic ring. Mass spectrum showed the formation of 1:2 metals to ligand stoichiometry. The antibacterial activity of synthesized compounds was evaluated by agar well diffusion method. All the synthesized compounds were evaluated for their DNA nicking activity and found most of metal complexes exhibited good DNA photocleavage activities.

Microwave synthesis, Characterisation and Biological activities of transition metal complexes with Novel SNSN Donor Schiff base ligand

A novel Schiff base (E)-N-(pyridine-2-yl)thiophen-2-ylmethylene)hydrazine carbothioamide (L), was synthesised by the condensation of thiophen-2-carbaldehyde and N-(pyridin-2-yl)-hydrazinecarbothiamide, using solvent free microwave synthesis. The Co(II), Ni(II), Cu(II) and Zn(II) complexes of the ligand were also prepared. They were characterised by elemental analysis, EI-mass spectrum, 1H & 13C-NMR spectrum, FTIR, UV-Vis spectra, magnetic, EPR spectra and thermal analysis. The “SNSN” donor ligand binds the metal ion in tetradentate mode through thiophenyl and thioenolic sulphur atoms and imino and pyridine nitrogen atoms. The electronic spectra along with magnetic measurements demonstrate tetrahedral geometry for Co(II), Ni(II) and Zn(II) complexes whereas square planar geometry for CuL complex. All the complexes were found to be thermally stable from thermogravimetric studies. The complexes show enhanced antibacterial activity than the ligand against various bacterial strains. The BSA binding activity of the complexes shows that the affinity for binding was greater towards copper complex. The cytotoxicity of the ligand and its complexes were tested on HT29 colon cancer cells using MTT assay.

Solvent-free Synthesis, Characterization and Biological Activity of Transition Metal Complexes of Schiff Base Ligand Derived from 2-Amino Benzimidazole with 4, 4’Dibromobenzil

Microwave-assisted synthesis and characterization of Schiff base ligand complexes of transition metals such as Mn(II), Fe(III), Co(II), Ni(II),Cu(II), Zn(II) Cd(II), and Ag(I) (using Schiff base) prepared by irradiation of 2-Amino benzimidazole with 4,4’dibromo benzil. The Synthesized transition metal complexes and Schiff base ligand have been representatively characterized by elemental analysis and spectral methods such as UV, IR, 1H-NMR, LC-MS, and Thermal analysis. The synthesized ligand and its complexes were also screened for their biological activities, such as antibacterial activity against bacterial species Staphylococcus aureus, Escherichia coli, and Salmonella Typhi. The result indicated that the complexes exhibited octahedral geometry.

Negative-ion field desorption revitalized by using liquid injection field desorption/ionization-mass spectrometry on recent instrumentation

Field ionization (FI), field desorption (FD), and liquid injection field desorption/ionization (LIFDI) provide soft positive ionization of gaseous (FI) or condensed phase analytes (FD and LIFDI). In contrast to the well-established positive-ion mode, negative-ion FI or FD have remained rare exceptions. LIFDI provides sample deposition under inert conditions, i.e., the exclusion of atmospheric oxygen and water. Thus, negative-ion LIFDI could potentially be applied to highly sensitive anionic compounds like catalytically active transition metal complexes. This work explores the potential of negative-ion mode using modern mass spectrometers in combination with an LIFDI source and presents first results of the application of negative-ion LIFDI-MS. Experiments were performed on two orthogonal-acceleration time-of-flight (oaTOF) instruments, a JEOL AccuTOF GCx and a Waters Micromass Q-TOF Premier equipped with LIFDI sources from Linden CMS. The examples presented include four ionic liquids (ILs), i.e., N-butyl-3-methylpyridinium dicyanamide, 1-butyl-3-methylimidazolium tricyanomethide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate), 3-(trifluoromethyl)-phenol, dichloromethane, iodine, polyethylene glycol diacid, perfluorononanoic acid, anionic surfactants, a tetraphosphazene silanol-silanolate, and two bis(catecholato)silanes. Volatile samples were delivered as vapors via the sample transfer capillary of the LIFDI probe or via a reservoir inlet. Condensed phase samples were applied to the emitter as dilute solutions via the sample transfer capillary. The compounds either yielded ions corresponding to their intact anions, A−, or the [M–H]− species formed upon deprotonation. This study describes the instrumental setups and the operational parameters for robust operation along with a discussion of the negative-ion LIFDI spectra of a variety of compounds.

Microwave Assisted Synthesis, Characterization and Biological Activity of Transition Metal Complexes of Schiff Base Ligand Derived from 2-Amino Benzimidazole with Isophthalaldehyde

Microwave Assisted Synthesis, Characterization and Biological Activity of Transition Metal Complexes of Schiff Base Ligand Derived from 2-Amino Benzimidazole with Isophthalaldehyde

Synthesis, structural characterization and biological activities of transition metal complexes derived from 2,4-dihydroxybenzaldehyde n(4)-methyl(phenyl)thiosemicarbazone

A new thiosemicarbazone, (E)-2-(2,4-dihydroxybenzylidene)-N-methyl-N-phenylhydrazinecarbothioamide (L) was synthesized. Single crystals were grown by slow evaporation of its ethanolic solution at room temperature. The grown crystals were characterized by SCXRD, elemental analyses, FT-IR, 1H NMR and UV-Vis spectral analyses. Complexes of L with Co(II), Ni(II) and Cu(II) chlorides were synthesized and their structures were elucidated by elemental analyses, FT-IR, 1H NMR, UV-Vis, EPR spectral analyses and magnetic moment measurements. All these compounds were tested against microbial strains. The free-radical-scavenging ability of the ligand and the metal complexes was measured by their interaction with the stable DPPH free radical and all the compounds showed appreciable antioxidant activity.

Synthesis, spectroscopic studies and pesticidal activity of transition metal complexes with unsymmetrical schiff base

Unsymmetrical Schiff base glyoxal salicylaldehyde succinic acid dihydrazide (gssdh), and their Co(II), Ni(II), Cu(II), and Zn(II) complexes have been synthesized and analyzed. These complexes' structures are explained based on magnetic, electronic, IR, and NMR (1H and 13C) spectral studies. These ligands show monobasic tetra-dentate behavior, bonding through C=O, two C=N, and a phenolate group. Ni(II) complex show square planar geometry while Cu(II) and Co(II) complexes exhibit tetrahedral geometry in the solid-state shown by electronic spectra. However, Co(II) and Cu(II) complexes adopt octahedral geometry in DMSO solution. The insecticidal activity of these compounds is tested, and compared their activity with their standard. Synthesized compounds show moderate insecticidal activity at higher concentrations. At low concentrations, these compounds have anti-fungal and antibacterial properties but do not show the pesticide property.

Synthesis, characterization and antimicrobial activity of transition metal complexes of 4-[(2-hydroxy-4-methoxyphenyl)methyleneamino]-2,4-dihydro-3H-1,2,4-triazole-3-thione

A novel nitrogen containing 3 H -1, 2, 4-triazole-3-thione-2, 4-dihydro-4-[(2-hydroxy-4-methoxyphenyl) methylene]-amino ligand (H 2 L) was synthesized using an equimolar ratio of 4-amino-1, 2, 4-triazole-3-thione and 2-hydroxy-4-methoxybenzaldehyde. A series of Mn (II), Fe (II), Co (II), Ni (II), Cu (II), Zn (II), Cd (II) transition metal complexes were synthesized using the ligand. The synthesized ligand and transition metal complexes were characterized by using IR, 1 H NMR, 13 C NMR, Mass spectrometry, UV, XRD and TGA investigation methods. Spectral data suggests that the ligand acts as a tridentate SNO donor. Further, the synthesized H 2 L ligand and their metal complexes were screened for antimicrobial activity. The results of biological activities showed that the metal complexes have higher antifungal as well as antibacterial activity as compared to the parent H 2 L ligand against the tested microbes.

Sublimable Spin-Crossover Complexes: From Spin-State Switching to Molecular Devices.

Spin‐crossover (SCO) active transition metal complexes are an important class of switchable molecular materials due to their bistable spin‐state switching characteristics at or around room temperature. Vacuum‐sublimable SCO complexes are a subclass of SCO complexes suitable for fabricating ultraclean spin‐switchable films desirable for applications, especially in molecular electronics/spintronics. Consequently, on‐surface SCO of thin‐films of sublimable SCO complexes have been studied employing spectroscopy and microscopy techniques, and results of fundamental and technological importance have been obtained. This Review provides complete coverage of advances made in the field of vacuum‐sublimable SCO complexes: progress made in the design and synthesis of sublimable functional SCO complexes, on‐surface SCO of molecular and multilayer thick films, and various molecular and thin‐film device architectures based on the sublimable SCO complexes.