Copper Complexes Research Articles

Synthesis and Spectroscopic Investigation of N-(Morpholinofurfuryl) Maleimide and its Copper (II) Complex uses in Biological Applications

The Mannich base N-(morpholinofurfuryl) maleimide (MOFM) is synthesized through a Mannich reaction using Maleimide as one of the starting materials. The reaction likely involves the condensation of Maleimide with formaldehyde and a secondary amine. It is then complexed with copper (II) to form the copper complex. This complexation process might involve reacting the Mannich base with a copper (II) salt under appropriate conditions. Characterization techniques such as FT-IR, UV–visible spectroscopy, 1H, and 13C NMR spectroscopy are used to confirm the formation of the complex and determine its structural features. The antioxidant properties of both the Mannich base ligand and its copper (II) complex are evaluated using assays such as DPPH (2,2-diphenyl-1-picrylhydrazyl) and reducing power assay. These assays assess the ability of the compounds to scavenge free radicals and reduce oxidative stress. It was found that MOFM had an IC50 value of 4.1762 x 10-4 and its Cu(II) complex had 2.5772 x 10-4 which confirms the ability of the prepared compounds to scavenge free radicals and reduce oxidative stress. The antimicrobial activity of the copper (II) complex of MOFM and the ligand is tested against various microorganisms including Aspergillus niger, Candida albicans, Escherichia coli, and Staphylococcus aureus using the agar-well diffusion method. Both the compounds had good antibacterial and antifungal properties. By conducting these experiments and analyses, you can gain insights into the structural features, antioxidant properties, and antimicrobial efficacy of both the Mannich base ligand and its copper (II) complex, which could have potential applications in various fields such as pharmaceuticals, materials science, or environmental protection.

Phenanthroline and phenyl carboxylate mixed ligand copper complexes in developing drugs to treat cancer

The success of a classic inorganic coordination compound, Cisplatin, cis-[Pt(NH3)2Cl2], as the first anticancer metallodrug started a field of research dedicated to discovering coordination compounds with antitumor activity, encompassing various metals. Among these, copper complexes have emerged as interesting candidates to develop drugs to treat cancer. In this work, mixed ligand complexes of Cu(II) with diimines (phenanthroline or 4-methylphenanthroline) and 3-(4-hydroxyphenyl)propanoate, phenylcarboxylate or phenylacetate were synthesized. They were characterized in the solid state, including a new crystal structure of [Cu2(3-(4-hydroxyphenyl)propanoate)3(phenanthroline)2]Cl·H2O. The obtained complexes presented a variety of stoichiometries. In solution, complexes were partially dissociated in the corresponding Cu-diimine complex. The complexes bound to the DNA by partial intercalation and groove binding, as assessed by Circular Dichroism, relative viscosity change and UV–Vis titration. The cytotoxicity of the complexes was determined in vitro on MDA-MB-231, MCF-7 (human metastatic breast adenocarcinomas, the first triple negative), MCF-10A (breast nontumoral), A549 (human lung epithelial carcinoma), and MRC-5 (human nontumoral lung epithelial cells), finding an activity higher than that of Cisplatin, although with less selectivity.

Nature of the chemical bonding and electronic structure of dicoordinated copper(I) complexes of alkenes, alkynes, and NHC ligands: a DFT overview

Nature of the chemical bonding and electronic structure of dicoordinated copper(I) complexes of alkenes, alkynes, and NHC ligands: a DFT overview

Synthesis, structural characterization, DFT and molecular dynamics simulations of dinuclear (μ-hydroxo)-bridged triethanolamine copper(II) complexes: efficient candidates towards visible light-mediated photo-Fenton degradation of organic dyes.

Multinuclear (di/tri) copper(II) complexes bridged through hydroxyl groups are very interesting coordination complexes owing to their potential applications in various fields. In this work, three novel dinuclear (μ-hydroxo)-bridged copper(II) complexes in the crystal form, namely, [Cu2(3,5-DIFLB)2(H2tea)2](H2O) (1), [Cu2(4-ClB)2(H2tea)2](H2O) (2), and [Cu2(4-ETHB)2(H2tea)2](H2O)2 (3) (where DIFLB = difluorobenzoate, CLB = chlorobenzoate, ETHB = ethoxybenzoate, and H3tea = triethanolamine), were isolated at room temperature using methanol and water in a 4 : 1 v/v ratio as a solvent. Furthermore, all three complexes (1-3) were characterised using spectroscopic (UV-vis, DRS, and FT-IR), electrochemical (CV) and single-crystal X-ray diffraction techniques. Structural insights gained by packing analysis revealed the role of steric constraints of substituents and various non-covalent interactions in lattice stabilization, which were indeed supported by theoretical and molecular electrostatic potential illustrations. Hirshfeld surface analysis provided quantitative verification about various non-covalent interactions (interatomic contacts) involved in the packing of molecules. Interestingly, as a potential application, complexes 1-3 all exhibited remarkable visible light-mediated photo-Fenton degradation of approximately 98% for 50 ppm concentration of organic dyes (fuchsin basic (FB) and methyl orange (MO)) in 90 minutes with the optimized conditions of 1 mg mL-1 of dye solution. In all the cases, dye degradation by these materials was ascribed to the symbiotic relations among the molecular structures of complexes 1-3, which were endowed with various electron-withdrawing and electron-releasing substituents and ionic strength, with respect to the structure, shape and interacting patterns of dye molecules. The adsorption mechanism indicates that various weak interactions between the donor and acceptor groups of complexes and dyes, such as electrostatic, hydrogen bonding, and direct coordination to metal sites, play a crucial role, which is confirmed by molecular dynamics (MD) simulations. Theoretical studies by DFT-based descriptors, molecular electrostatic potentials, and band gaps provided deep insights into various electronic and reactivity parameters. For subsequent processes of dye degradation, complexes 1-3 were stable and recoverable. The successful integration of experimental and theoretical approaches sheds light on copper-based dinuclear stable coordination complexes, showcasing a significant step towards the development of novel heterogeneous photo-Fenton catalysts.

Effect of Bipyridines on Catalytic Oxygen Reduction by Oxamidato‐Bridged Dicopper(II) Complexes

ABSTRACTThe oxygen reduction reaction (ORR) has a crucial impact on the energy conversion efficiency and the performance of fuel cells, it is urgent to deliver low‐cost efficient ORR catalysts for the aim to scale up the utilization of fuel cells. In this study, three oxamidate copper(II) complexes [Cu2(trans‐L)(H2O)2(ClO4)2]·2H2O (Cuox), [Cu2(cis‐L)(bpy)(ClO4)2]·CH3OH (Cuoxbpy), and [Cu2(cis‐L)(mebpy)(ClO4)](ClO4) (Cuoxmebpy) (L = N,N–bis(2–pyridylmethyl)oxamide, bpy = 2,2′–bipyridine, and mebpy = 4,4′–dimethyl–2,2′–bipyridine) were prepared and characterized. The configuration of L varied from the trans form to the cis form as the bipyridines were introduced to the dicopper complex. The redox properties of three oxamidate copper(II) complexes and their catalytic activities for the ORR were studied in neutral aqueous solutions. The ORR onset potentials by Cuox, Cuoxbpy, and Cuoxmebpy were 0.417, 0.502, and 0.481 versus RHE, respectively. Three complexes homogeneously catalyzed the ORR to predominantly generate H2O2. A bimolecular catalytic pathway was proposed for the ORR mediated by Cuox, whereas a single‐molecular pathway was by Cuoxbpy and Cuoxmebpy. This work demonstrated that oxamidate metal complexes are promising ORR catalyst candidates provided that their electronic structures are appropriately tuned by altering the substituent on the organic ligands.

3D fabrication of complex copper microstructures with path planning by localized electrochemical deposition

3D fabrication of complex copper microstructures with path planning by localized electrochemical deposition

Hybrid Organic-Inorganic Copper and Cobalt Complexes for Antimicrobial Potential Applications

Background/Aims: The naturally occurring phenolic chemical curcumin (CUR), which was derived from the Curcuma longa plant, has a variety of biological actions, including anti-inflammatory, antimicrobial, antioxidant, and anticancer activities. Curcumin is known for its restricted bioavailability due to its hydrophobicity, poor intestinal absorption, and quick metabolism. To boost the biological effects of these bioactive molecules, it is necessary to raise both their bioavailability and their solubility in water. Aim: The aim of this study is to synthesize and characterize hybrid organic-inorganic complexes of copper and cobalt, and to evaluate their antimicrobial potential against a range of pathogenic microorganisms. Methods: The synthesis of metal curcumin complexes (Cu-CUR and Co-CUR) was achieved by mixing curcumin with copper acetate monohydrate. The solid residue was isolated, filtered, and dried in an oven. X-ray diffraction analysis was used to identify the structure and phase of the prepared samples. FTIR spectra were recorded using a Shimadzu 2200 module. The antimicrobial activity of the prepared complexes was evaluated against four bacterial strains and two Candida species. The chemical materials were dissolved in DMSO to a final concentration of 20%, and the plates were incubated at 37°C for 24 hours. The results showed that the prepared complexes had antimicrobial activity against the tested microorganisms. Results: The study compared the Powder X-ray diffraction (XRD) patterns of prepared copper and cobalt complexes to pure curcumin, revealing new, isostructural complexes. The FTIR analysis showed that the Cu-CUR and Co-CUR complexes varied in their inhibitory effect against microorganisms, with Co-CUR being more effective. The results are consistent with previous studies showing the cobalt-curcumin complex was effective against various bacterial genera, with inhibition activity varying depending on the species and strains of microorganisms. Conclusion: Copper and cobalt curcumin complexes, synthesized at room temperature, exhibit high crystallinity and antimicrobial activity. Co-CUR, with its superior antibacterial potential, outperforms pure curcumin in inhibiting microbes. Further investigation is needed to understand their interaction mechanisms with bacteria and fungi.

Development of pivalic acid conjugated Nafion modified glassy carbon electrode for sensitive detection of Cu(II) by electrochemical approach

In this work, pivalic acid (pivH) molecule is employed for an electrochemical sensing of copper cations in an aqueous medium. For sensitive as well as selective potential sensor application, pivH was fabricated onto a glassy carbon electrode (GCE) facilitated by adhesive conducting binder, nafion, so as make it selective and effective electrochemical probe (pivH/Nafion/GCE) towards specific heavy metal cations. This newly fabricated pivH/Nafion/GCE reveals enhance electrochemical activity toward copper ions in the presence of other interfering heavy metal cations in phosphate buffer solution (PBS) of pH=7. The calibration plot was linear (r2 = 0.9879) across broad linear dynamic range (LDR) spanning Cu2+ concentration from 0.1 nM to 0.01 M. The sensitivity and detection limit was found to be 0.0212 × 10−2 µAµM−1cm−2 and 0.014 nM, respectively. So, this newly fabricated GCE as selective electrochemical probe offers a sensitive as well as selective detection of Cu2+ cations in real environmental samples using a novel electrochemical, current–potential (I-V), approach, for the first time. Further, we explored pivalic acid for the preparation of new di-nuclear copper complex, [Cu2(piv)4(pivH)2] (where piv = pivalate; pivH=pivalic acid) and characterized by Fourier transform infrared spectroscopy (FTIR) spectroscopy, elemental analysis and single crystal X-ray diffractometry. Density functional theory (DFT) calculations were carried out to confirm the interactions and these calculations well-support to experimental data. In case of deprotonated form of pivH, Molecular Electrostatic Potential (MEP) analysis exhibits electrostatic potential equals to −148.4 kcal/mol which suggest about the strong interaction of –COOH with copper centers. Similarly, interaction energies, the quantum theory of atoms in molecules (QTAIM) study and Natural Bond Orbital (NBO) analysis also favor to experimental work. Thus, this novel study demonstrates an excellent approach for highly selective and sensitive detection of Cu2+ cations in short response time with low detection limit and good reproducibility by using I-V method based on newly designed pivH/Nafion/GCE as selective Cu2+ cationic electrochemical sensor. The experimental data was compactable with theoretical calculations.

Metal complexes featuring a quinazoline schiff base ligand and glycine: synthesis, characterization, DFT and molecular docking analyses revealing their potent antibacterial, anti-helicobacter pylori, and Anti-COVID-19 activities

Mixed ligand complexes of manganese(II), cobalt(II), copper(II), and cadmium(II)with an innovative Schiff base ligand denoted as (L1), 4-(2-((1E,2E)-1-(2-(p-tolyl)hydrazineylidene)propan-2-ylidene)hydrazineyl), served as the principal ligand, while glycine (L2) was employed as secondary ligand were successfully effectively characterized through a comprehensive set of analyses, including Elemental analysis, UV–Visible, FT-IR, Mass spectra, and conductometric measurements. Density functional theory (DFT) computations were executed to discern the enduring electronic arrangement, the energy gap, dipole moment and chemical hardness of the hybrid ligand assemblies. The proposed geometry for the complexes is a distorted octahedral structure. The antimicrobial efficacy of these compounds was assessed against a range of bacterial and fungal strains. Notably, these complexes exhibited promising antimicrobial activities, with the cadmium (II) complex demonstrating superior efficacy towards all tested organisms. These compounds were also examined for their antibiotic properties against H. pylori to explore their broader medical potential. The Schiff base ligand and its corresponding metal complexes displayed substantial potential as an antibiotic against H. pylori. Additionally, the antitumor potential of the synthesized complexes was assessed against MCF-7 (Breast carcinoma) cells—the Cu (II) complex demonstrated superior activity with the lowest IC50 value compared to cisplatin. Moreover, it exhibited reduced cytotoxicity towards normal cells (VERO cells) compared to cisplatin, establishing it as the most potent compound in the study. Furthermore, molecular docking was explored of the Schiff base ligand and its corresponding cadmium(II) complex. The analysis of the docking study yielded valuable structural insights that can be effectively utilized in conducting inhibition studies for example against COVID-19. This comprehensive study highlights these synthesized compounds' multifaceted applications and promising bioactive properties.

Azolylphenanthridine-ligated Cu(II) catalyst for electrochemical oxidation of cholesterol in aprotic medium

The synthesis of original 6-(azol-1-yl)phenanthridine ligands and a copper(II) complex based on them is reported. Comprehensive studies of the structural, physicochemical, and electrocatalytic properties for the selected 6-(1H-pyrazol-1-yl)phenanthridine-containing coordination compound have been carried out. The latter has demonstrated pronounced electrochemical and electrocatalytic activities in the enzyme-free cholesterol oxidation in DMSO. A six-stage mechanism including electrocatalytic reduction of cholesterol and subsequent oxidation of its reduction products has been proposed and underpinned by quantum mechanical considerations. Obtained analytical characteristics of the enzyme-free cholesterol oxidation (LoD 0.0032 mM, detectable concentrations 0.01–0.40 mM) open a prospect towards the investigated complexes to be applied as sensitive elements of portable electrochemical platforms for the point-of-care diagnostics.

Carrier-free nanoparticles based on self-assembly of 5-FU and copper-genistein complexes for the combined treatment of hepatocellular carcinoma.

5-Fluorouracil (5-FU) is commonly used as a chemotherapeutic drug for advanced HCC. However, the effectiveness of 5-FU is limited by the emergence of resistance and poor targeting efficiency. Combining 5-FU with natural compounds has shown promise in HCC treatment. In this study, we prepared carrier-free nanoparticles (GEN-Cu-GEN@FUA) containing 5-FU and genistein (GEN) in a synergistic ratio via a green synthesis procedure. The resulting GEN-Cu-GEN@FUA nanoparticles had a spherical or near spherical shape, a dynamic size of 129.3 ± 40.1nm, and a high drug loading content of approximately 21.40% (5-FU) and 61.48% (GEN). These nanoparticles exhibited approximately 3.6-fold lower IC50 value than 5-FU alone in Bel-7402 cells and resulted in a 3.7-fold greater reduction in tumor weight compared to 5-FU alone in Bel-7402 tumor-bearing BALB/c mice. Importantly, the nanoparticles showed negligible systemic toxicity due to their synergistic effect on cancer cell dysfunction and significant amplification of intracellular glutathione consumption. Our findings suggest that the developed carrier-free nanomedicines offer a highly promising platform for the co-delivery of genistein (GEN) copper(II) complexes and 5-FU, with easy fabrication and great potential for clinical translation in HCC synergistic therapy.

Water-Insoluble Copper Complexes As Electrocatalysts for CO2 Reduction

The electrochemical reduction of carbon dioxide (CO2R) constitutes a promising CO2 utilization technology, allowing the production of valuable fuels and chemicals by using electrical energy from renewable sources. Nevertheless, poor selectivity and high required overpotentials hamper practical applications of the CO2R, which highlights the need for the development of more efficient electrocatalysts. Different copper-based materials have been extensively studied as electrocatalysts for CO2R. Particularly, copper complexes exhibited interesting properties under operational conditions: many of them undergo structural modifications (e.g. changes in oxidation state and/or coordination number), which potentially affect activity, selectivity and stability. Interestingly, some complexes exhibit reversible restructuring under specific conditions, which can be an interesting property to reach higher stability. In this presentation, we will show the results obtained for the electrocatalysis of water-insoluble copper complexes for the CO2R. The activity, selectivity and stability of both [Cu(bzimpy)Cl2] and [Cu(pyrben)2(NO3)]NO3 were investigated in K2SO4 0.1 mol L-1 (CO2 sat.) under different electrochemical conditions. Here, bzimpy and pyrben stand for 2,6-bis(2-benzimidazolyl)pyridine and 2-(2-pyridyl)benzimidazole, respectively. Qualitative EC-MS (Electrochemistry Coupled to Mass Spectrometry) analysis evidenced that both complexes are active for CO2 reduction and that product distribution changes according to the applied potential. Quantitative gas chromatography measurements revealed that, at -1.24 V vs. RHE, [Cu(bzimpy)Cl2] promotes the formation of H2, CO, CH4 and C2H4 with faradaic efficiencies of 26, 3.4, 9.2 and 31%, respectively. On the other hand, [Cu(pyrben)2(NO3)]NO3 shows FE values of 24, 8.8, 15 and 24% for H2, CO, CH4 and C2H4, respectively. After 1.6 h of electrolysis, the former exhibited stable current and FE of ~42% towards ethylene formation.

Size and Electronic Effects on Redox Potentials and Electrocatalytic Processes Performed by Corrole-Chelated Metal Complexes

The future of our planet critically depends on the introduction of new or improved strategies for developing non-polluting energy production. Leading approaches are the electrocatalytic production of hydrogen gas, development of fuel cells relying on efficient reduction of oxygen and either gaseous or liquid fuels, as well as efficient reduction of carbon dioxide. Metal complexes chelated by N4 macrocycles serve as excellent catalysts in many of these processes, performed at both homogeneous and heterogeneous conditions. Our contributions to those aspect focused on introducing metallocorroles as catalysts for reduction of protons, oxygen and carbon dioxide, as well as for water oxidation [1-5]. The common motif in these and other publications was to take advantage of the relatively easy functionalization of the macrocyclic periphery for the tuning of properties and reactivity. A significant game changer was the recently reported synthetic access to corroles with meso-CF3 substituents and even to the parent corrole with no substituents whatsoever [6]. These developments allow for a focus on the size effect, which according to both hypothesis and fast accumulating results has a very strong effect (“smaller is better”) on the performance of electrodes modified by the corresponding metal complexes [7-9].References Sinha, N. Fridman, Y. Diskin-Posner, L. J. W. Shimon and Z. Gross “Superstructured Metallocorroles for Electrochemical CO2 Reduction”, Chem. Commun. 2019, 55, 11912-11915.Sinha, A. Mahammed, N. Fridman and Z. Gross “Water Oxidation Catalysis by Mono- and Binuclear Iron Corroles” ACS Catal. 2020, 10,3764-3772.Sudhakar, A. Mahammed, Q.-C. Chen, N. Fridman, B. Tumanskii and Z. Gross “Copper Complexes of CF3‐Substituted Corroles for Affecting Redox Potentials and Electrocatalysis” ACS Appl. Energy Mater. 2020, 3, 2828-2836.Yadav, I. Nigel-Etinger, A. Kumar, A. Mizrahi, A. Mahammed, N. Fridman, S. Lipstman,I. Goldberg, and Z. Gross “Hydrogen Evolution Catalysis, by Terminal Molybdenum-Oxo Complexes”, Iscience 2021, 24, 102924.-C. Chen, S. Fite, N. Fridman, B. Tumanskii, A. Mahammed, and Z. Gross “Hydrogen Evolution Catalyzed by Corrole-Chelated Nickel Complexes, Characterized in all Catalysis-relevant Oxidation States”, ACS Catalysis 2022, 12, 4310−4317.Kumar, P. Yadav, M. Majdoub, I. Saltsman, N. Fridman, S. Kumar, A. Kumar,A. Mahammed and Z. Gross “Corroles: The Hitherto Elusive Parent Macrocycle and its Metal Complexes” Angew. Chem. 2021, 60, 25097-25103. Mahammed and Z. Gross “Milestones and Most Recent Advances in Corrole’s Science and Technology”, J. Am. Chem. Soc. 2023, 145, 12429–12445Raslin, J. Douglin, A. Kumar, M. Fernandez-Dela-Mora, D. Dekel and Z. Gross “Size and electronic effects on the performance of (corrolato)cobalt-modified electrodes for ORR catalysis”. Inorg. Chem. 2023, 62, 14147–14151.Kumar, S. Fite, A. Raslin, S. Kumar, A. Mizrahi, A. Mahammed, and Z. Gross “Beneficial Effects on the Cobalt-Catalyzed Hydrogen Evolution Reaction Induced by Corrole Chelation”. ACS Catal. 2023, 13, 13344-13353. Figure 1

Copper Corrole Electropolymers

The electrochemical polymerization of the copper complex of 5,10,15-tris-(4-aminophenyl) corrole leads to the formation of conductive films, which have been deposited onto interdigitated electrodes to develop chemoresistive sensors. These devices are of interest because of their facile miniaturization and integration into low-cost electronic circuits. It is interesting to note that the properties of these films, such as morphology, semiconducting nature and sensitivity, can be tuned by modifying the synthetic electropolymerization protocols. This opportunity can allow the preparation of cross-selective sensors that can be integrated into miniaturized conductometric electronic nose platforms.

Synthesis of copper complexes for potential use in the diagnosis of Alzheimer's disease

Background: Since there is currently no cure for Alzheimer's disease (AD), it is important to develop methods that could contribute to its diagnosis and propose new therapeutic approaches for its treatment. Positron emission tomography (PET) is a medical imaging technique that can be used to diagnose Alzheimer's disease, as some radiotracers have been developed to detect amyloid plaques, one of the hallmarks of the disease. However, the radiotracers already used for the diagnosis of AD have a low half-life, which limits their use over the time and requires the presence of a cyclotron close to the examination site. The use of copper complexes could be a good alternative for the development of new radiotracers, since they can be used in PET imaging and have a longer half-life than the other radiotracers already used for AD diagnosis. Aim of the study: Design and synthesize copper complexes that could be used as PET radiotracers able to cross the blood brain barrier and detecting amyloid plaques.Material and methods: The first objective was to design a series of new copper complexes with the capacity to target amyloid plaques inside the brain and contribute to the rational synthesis of such complexes. To this end, theoretical models were used to predict the ability of the complex to cross the blood-brain barrier (BBB) which separates brain from de blood and is main gatekeeper for drugs entering the brain. The models employed consider the physicochemical properties of the molecules. Based on these models, one of the molecules was synthesized in ten steps. The key step in the synthetic strategy was the coupling of a monopicolinate-N-alkylated cyclam-based ligand with a moiety capable of recognizing Aβ plaques via a Buchwald-Hartwig coupling reaction. Potentiometric, spectrophotometric and electron paramagnetic resonance spectroscopic studies were performed to determine the structure and thermodynamic stability of the complex. In addition, the ability to target amyloid plaques was evaluated using brain sections from Alzheimer's disease patients and the cytotoxicity was evaluated using human neuronal cells.Results: A first complex has been designed and synthesized. The physicochemical studies performed indicate that this complex seem to be thermodynamically stable. In addition, cytotoxicity tests on human neuronal cells indicate low toxicity and labeling tests on brain sections from Alzheimer's patients suggest that the complex is capable of recognizing amyloid plaques. Conclusion: We have developed a novel copper complex that is able to detect recognize amyloid plaques. In the future this molecule could be used in PET and contribute to the diagnosis of Alzheimer's disease. From these results, we also propose to develop a new copper complex for tau PET imaging.

SCN as a local probe of protein structural dynamics.

The dynamics of lysozyme is probed by attaching -SCN to all alanine residues. The one-dimensional infrared spectra exhibit frequency shifts in the position of the maximum absorption of 4 cm-1, which is consistent with experiments in different solvents and indicates moderately strong interactions of the vibrational probe with its environment. Isotopic substitution 12C → 13C leads to a redshift by -47 cm-1, which agrees quantitatively with experiments for CN-substituted copper complexes in solution. The low-frequency, far-infrared part of the protein spectra contains label-specific information in the difference spectra when compared with the wild type protein. Depending on the position of the labels, local structural changes are observed. For example, introducing the -SCN label at Ala129 leads to breaking of the α-helical structure with concomitant change in the far-infrared spectrum. Finally, changes in the local hydration of SCN-labeled alanine residues as a function of time can be related to the reorientation of the label. It is concluded that -SCN is potentially useful for probing protein dynamics, both in the high-frequency part (CN-stretch) and in the far-infrared part of the spectrum.

Modified nanomagnetite silica core shell with new Cu (II) N,N‐ chelating complex as an efficient and reusable catalyst in the C‐N bond formation

In this article, initially, the TCTCl (DiPrAEA)2 ligand was synthesized and characterized by Fourier transform infrared (FT‐IR), X‐ray crystallography, 1H‐ and 13C‐NMR spectroscopy, and elemental analysis. The crystallographic structure data for the ligand has been deposited at the Cambridge Crystallographic Data Centre (CCDC No. 2282732). Then, using of this novel multidentate ligand, a novel and stable copper (II) nanocatalyst complex was synthesized by anchoring copper (II) acetate onto the core‐shell surface (Fe3O4@SiO2) via the novel multidentate ligand TCTCl (DiPrAEA)2. The successful synthesis of the Fe3O4@SiO2‐NH‐TCT (DiPrAEA)2‐Cu (II) nanocatalyst was confirmed by employing physicochemical techniques such as FT‐IR, X‐ray diffraction, ultraviolet‐visible, thermogravimetric analysis, X‐ray photoelectron spectroscopy, Brunauer–Emmett–Teller, energy‐dispersive X‐ray, dynamic light scattering, inductively coupled plasma, transmission electron microscopy, field emission scanning electron microscopy, and vibrating sample magnetometer. Subsequently, this novel copper (II) nanomagnetic complex was evaluated as an efficient, reusable, and novel catalyst for the formation of C‐N bonds via the Ullmann coupling reaction of aryl halides and nitrogen‐containing compounds. The influence of this novel TCTCl (DiPrAEA)2 ligand on the reactivity and stability of the nanomagnetic copper complex was visible in the Ullmann reaction, which resulted in rapid reaction times and excellent yields, and seven times reusability.

Recyclable Ni(II), Cu(II), and Co(II) complexes containing Schiff base immobilized on nanosilica as catalysts in oxidation of hydrocarbons

Metal complexes (M=Ni, Cu, and Co) containing Schiff base have been synthesized and characterized using the usual coordination chemistry techniques. The complexes were immobilized in silica nanoparticle functionalized with a Schiff base (SB) and the heterogeneous catalysts were characterized by infrared spectroscopy, Scanning electron microscopy (SEM) and determination of the surface area (BET). Thermogravimetric analysis (TGA) of metal concentration was conducted using atomic absorption spectroscopy. The catalysts were studied in the oxidation reaction of hydrocarbons at 50 °C using H2O2 or tert-butyl hydroperoxide (TBHP) as oxidant. The heterogeneous catalysts NPs-SiO2-SB-Co(II) (catalyst 1), NPs-SiO2-SB-Cu(II) (catalyst 2), and NPs-SiO2-SB-Ni(II) (catalyst 3) showed moderate activities in the oxidation of cyclohexane, toluene, and benzene using H2O2 as oxidant. The results indicated that catalyst 2 displayed better activity in the oxidation of cyclohexane, toluene, and benzene. The best activity was obtained at 50 °C with the following conversions: 88 %, 78 %, and 66 % for cyclohexane, toluene and benzene, respectively. The results of the recycling experiment revealed that the copper complex immobilized in mesoporous silica nanoparticle maintains its catalytic activity after 4 cycle.

ESR, UV–vis–NIR and FTIR spectroscopic characterization of charge carriers in copper salen polymeric complexes

In this work, we present spectroscopic investigation of charge carriers in copper(II) salen-type polymeric complexes. The polymers comprising monomeric complexes of copper(II) ion with N2O2 Schiff base ligands are analyzed to understand the influence of the paramagnetic metal center and electron-donating substituents in the ligand on the spectroscopic properties of oxidized polymers. Potential-driven structural changes in the polymeric complexes were monitored using electron spin resonance (ESR), ultraviolet−visible − near infrared (UV−vis − NIR) and Fourier Transform Infrared (FTIR) spectroelectrochemistry. By EPR spectroelectrochemistry, we gained insight into the magnetic properties of charge carriers formed during the initial and deep oxidation of the polymers as well as the interactions between the Cu(II)–ligand spins and ligand–ligand ones. By FTIR spectroelectrochemistry, it has been shown that the charge in the low doped polymers is delocalized within the whole repeat unit.

Structural characterization and anticancer studies of copper(II) and cobalt(III) complexes containing N,O-donor heterocyclic chelators

New Cu(II) and Co(III) complexes were synthesized from reaction of 3-((E)-1-(((E)-4-(diethylamino)-2-hydroxybenzylidene)hydrazono)ethyl)-8-methoxy-2H-chromen-2-one (HL) with Cu(NO3)2·3H2O and Co(NO3)2·6H2O in methanol. The synthesized compounds were characterized by various analytical and spectral (IR, UV-Vis, NMR, EPR, ESI-MS and HR-MS) techniques. From the spectral studies, we concluded that the formation of the ligand and complexes. In the copper complex with formula of [Cu2(L)(NO3)3(H2O)], HL coordinated to copper ion via azomethine nitrogen, lactone oxygen, azomethine nitrogen and oxalate oxygen atoms. In cobalt complex, the ligand coordinated to cobalt ion via ring carbonyl oxygen, azomethine nitrogen, oxalate oxygen and azomethine nitrogen, and the complex is of ML2 type with the general formula [CoL2]·2NO3. The cytotoxic nature of the compounds was analyzed with human liver cancer cells (HepG2) and human breast cancer cells (MM2), in which the complexes exhibited a comparable activity than the positive control cisplatin. The IC50 values of the compounds were greater than 200 μM for non-cancerous human umbilical vein endothelial (HUVEC) cells, indicating selectivity of the compounds towards cancer cells rather than normal cells. The apoptogenic natures of the complexes with HepG2 and MM2 cancer cells were confirmed using AO-EB and DAPI staining assays. These results revealed the possibility of developing highly active cobalt and copper complexes as anticancer agents.