Presence Of Phenanthroline Research Articles

Iron- and base-catalyzed C(α)-alkylation and one-pot sequential alkylation-hydroxylation of oxindoles with secondary alcohols.

The utilization of economical and environmentally benign transition metals in crucial catalytic processes is pivotal for sustainable advancement in synthetic organic chemistry. Iron, as the most abundant transition metal in the Earth's crust, has gained significant attention for this purpose. A combination of FeCl2 (5 mol%) in the presence of phenanthroline (10 mol%) and NaOtBu (1.5 equivalent) proved effective for the C(α)-alkylation of oxindole, employing challenging secondary alcohol as a non-hazardous alkylating agent. The C(α)-alkylation of oxindole was optimized in green solvent or under neat conditions. The substrate scope encompasses a broad array of substituted oxindoles with various secondary alcohols. Further post-functionalization of the C(α)-alkylated oxindole products demonstrated the practical utility of this catalytic alkylation. One-pot C-H hydroxylation of alkylated oxindoles yielded 3-alkyl-3-hydroxy-2-oxindoles using air as the most sustainable oxidant. Low E-factors (3.61 to 4.19) and good Eco-scale scores (74 to 76) of these sustainable catalytic protocols for the alkylation and one-pot sequential alkylation-hydroxylation of oxindoles demonstrated minimum waste generation. Plausible catalytic paths are proposed on the basis of past reports and control experiments, which suggested that a borrowing hydrogen pathway is involved in this alkylation.

Exploring the copper(II) coordination to 2′-hydroxy-4-benzyloxychalcone analogues and their potential pharmacological applications

Chalcones are chemical precursors of flavonoids and exhibit a variety of biological properties, including anti-cancer, anti-inflammatory, and anti-malarial activities. According to the literature, different transition metal complexes of chalcones exhibit antitumor and antibacterial properties. Herein we report the synthesis, characterization, and the in vitro evaluation of antileishmanial, antiproliferative, and antiviral activities of novel copper(II)-2′-hydroxy-4-benzyloxychalcone complexes. Two of the complexes (1 and 2) had the formula [Cu(L)2], and the other two (3 and 4) were characterized as [Cu(L)(phen)Cl], where L is the deprotonated form of the 2′-hydroxy-4-benzyloxychalcones (HL1, is a fluorine substituted analog of HL2) and phen is 1,10- phenanthroline. Structures resolved by single-crystal X-ray diffraction showed that complexes 3 and 4 had a distorted square pyramid geometry, with chloride at the apical position. The stability of the complexes in dimethyl sulfoxide showed a significant variation. A wide range of ligand exchange kinetics was observed in the solution, influenced by chalcone fluorination and the presence of phenanthroline. Potential pharmacological applications were evaluated using in vitro assays for anti-proliferative, leishmanicidal, and antiviral activities. Complexes 1 and 3 showed cytostatic effects against the human breast tumor cell line (MCF-7, GI50 = 4.6 and 1.0 µM, respectively) that could be attributed to the free ligand HL1 (MCF-7, GI50 = 1.16 µM). Moreover, complex 1 showed higher selectivity to MCF-7 cells in comparison to murine immortalized 3T3 cells (GI50 > 100 µM). Complex 2 was inactive and toxic while complex 4 showed an unspecific cytostatic effect. Despite a weak leishmanicidal activity, at 25 µM, complex 3 inhibited (85,1 %) the SARS-CoV-2 replication at 2 µM. As complex 4 also showed good antiviral activity against SARS-CoV-2 (84,7 %), the antiviral activity seems to be related to copper(II)-phenanthroline fragment. This work demonstrates how simple changes in the structure of the ligand affect ligand exchange reactions and, consequently biological activity. It also expands the biological applications of Cu(II) chalcone complexes.

Non-covalent ligand-oxide interaction promotes oxygen evolution

Strategies to generate high-valence metal species capable of oxidizing water often employ composition and coordination tuning of oxide-based catalysts, where strong covalent interactions with metal sites are crucial. However, it remains unexplored whether a relatively weak “non-bonding” interaction between ligands and oxides can mediate the electronic states of metal sites in oxides. Here we present an unusual non-covalent phenanthroline-CoO2 interaction that substantially elevates the population of Co4+ sites for improved water oxidation. We find that phenanthroline only coordinates with Co2+ forming soluble Co(phenanthroline)2(OH)2 complex in alkaline electrolytes, which can be deposited as amorphous CoOxHy film containing non-bonding phenanthroline upon oxidation of Co2+ to Co3+/4+. This in situ deposited catalyst demonstrates a low overpotential of 216 mV at 10 mA cm−2 and sustainable activity over 1600 h with Faradaic efficiency above 97%. Density functional theory calculations reveal that the presence of phenanthroline can stabilize CoO2 through the non-covalent interaction and generate polaron-like electronic states at the Co-Co center.

SYNTHESIS OF COMPLEX OXIDES OF COBALT-NEODYMIUM FROM HETEROCOMPLEXES AND THEIR CATALYTIC ACTIVITY IN THE DE­COM­POSITION OF HYDROGEN PEROXIDE

New heterometallic complexes of Сo(II) and Nd(III) with carboxylic acids (succinic, oxalic) and acetylacetone in the presence of phenanthroline or α,α'-dipyridyl have been synthesized. Their thermal properties and the ability to form complex oxides during thermal degradation have been studied. In the process of thermolysis of heterocomplexes, neodymium cobaltate NdCoO3 was obtained, which is confirmed by the results of X-ray powder diffraction.
 The research has established that the X-ray powder diffraction patterns of the products obtained by thermolysis of heterocomplex [Сo2Nd2(C4Н4O4)5·2Phen]·4Н2О to 1000 °С exhibits peaks at (2θ): 23.40, 33.74, 41.42, 48.32, 54.52, 59.94, 70.58°. This corresponds to the neodymium cobaltate NdCoO3. Neodymium cobaltate crystallizes in the cubic crystal system. The sample was obtained without extraneous phases inclusions. For the samples obtained by the termolysis of he­te­rocomplexes [Сo2Nd2(C2O4)5·2Phen]·4Н2О and NdCo(AA)5·2α,α'-dipy, in addition to the complex oxide NdCoO3, peaks of Nd2O3 were recorded, which crystallizes in the hexa­gonal crystal system. The X-ray powder diffraction patterns show peaks with 2θ values: 26.92, 29.75, 30.77, 40.54, 47.53, 53.63, 57.08°. The phase ratio of NdCoO3/Nd2O3 after termolysis for the sample of CoNd(AA)5·2α,α'-dipy is ~ 68.9/31.1%; for the sample of [Сo2Nd2(C2O4)5·2Phen]·4Н2О is ~ 50/50%; for the sample of [Сo2Nd2(C4Н4O4)5·2Phen]·4Н2О is NdCoO3 ~ 100%. The average crystallites size of complex oxides was calculated using the Scherer formula. It has been showed that neodymium cobaltate has an average particle size of ~33 nm, regardless of the complex precursor from which it was formed during thermolysis.
 The catalytic effect of neodymium cobaltates in the hydrogen peroxide decomposition reaction was studied. It was shown that all samples of complex oxides showed a quite high cataly­tic activity in the all of experiments in the hydro­gen peroxide decomposition reactions.

On the Copper-Promoted Backbone Arylation of Histidine-Containing Peptides Using Triarylbismuthines

AbstractWe report herein our detailed investigation on the histidine-directed backbone arylation of histidine-containing peptides using triarylbismuth reagents. The reaction proceeds on the backbone NH of the amino acid that precedes the histidine, the so-called n–1 position. The protocol is applicable to dipeptides where the histidine is located at the C-terminus and to tripeptides where the histidine occupies the central position. The transformation is promoted by copper(II) acetate in the presence of phenanthroline (Phen) and diisopropylethylamine in dichloromethane at 50 °C under oxygen. An excellent scope was observed for the triarylbismuthines. In all cases, the imidazole ring of the histidine is protected with a trityl group to prevent the arylation of the side chain. An ATCUN-like model is proposed to explain the observed results.

Room-temperature direct alkynylation of arenes with copper acetylides.

C-H bond in azoles and polyhalogenated arenes can be smoothly activated by copper acetylides to give the corresponding alkynylated (hetero)arenes by simple reaction at room temperature in the presence of phenanthroline and lithium tert-butoxide under an oxygen atmosphere. These stable, unreactive, and readily available polymers act as especially efficient and practical reagents for the introduction of an alkyne group to a wide number of arenes under remarkably mild conditions.

Nickel-Catalyzed Negishi Cross-Coupling Reactions of Secondary Alkylzinc Halides with 6-Chloropurines

An efficient method for the synthesis of 6-acyclic secondary alkyl purines was developed via nickel-catalyzed Negishi cross-cupling of 6-chloropurines with acyclic secondary alkylzinc halides in the presence of phenanthroline at room temperature. The process gave good to excellent isolated yields under very mild conditions.

1,10-Phenanthroline-Catalysed Cr(Vi) Oxidation of D-Sorbitol and D-Mannitol in Aqueous Micellar Media

Chromic acid oxidation of two polyols (D-sorbitol and D-mannitol) to their corresponding aldohexoses in the presence of phenanthroline (phen) involves as the active oxidant, a Cr(VI)-phen complex formed in a rapid pre-equilibrium step. The observed micellar effect (rate acceleration by an anionic surfactant and rate retardation by a cationic surfactant) conforms with the proposed reaction mechanism.

Comparative evaluation of Fe(III) reducing power-based antioxidant capacity assays in the presence of phenanthroline, batho-phenanthroline, tripyridyltriazine (FRAP), and ferricyanide reagents

The chemical diversity of antioxidants in complex matrices such as plant extracts makes it difficult to separate and quantify antioxidants from these solutions. Therefore it is desirable to establish methods that can measure the total antioxidant capacity (TAC) levels directly from plant extracts. Iron(III)-based TAC assays, especially the most widely used FRAP (ferric-reducing antioxidant power), play an important role in this regard. However, many problems have been reported in the application of the FRAP assay, the most serious one being the incomplete oxidation of a number of antioxidants during the time protocol of the assay. Thus, six different ferric ion-based total antioxidant capacity (TAC) assays have been comparatively tested, modified, and improved so as to obtain more sensitive and precise results for complex mixtures, namely: 1,10-phenanthroline ( o-phen) method (with incubation), batho-phenanthroline method (with incubation), original FRAP method, modified FRAP method (with incubation), original ferricyanide method, and modified ferricyanide method (with incubation). Two new assays in this regard (i.e., o-phen and batho-phen) have been established, and the existing assays (FRAP and ferricyanide) have been modified so as to let the oxidation reactions of antioxidants reach completion. The molar absorptivity for a variety of antioxidants was highest for modified FRAP, batho-phen, and original FRAP methods. The absorption maximum wavelength shifted batochromically to a higher extent for modified ferricyanide, FRAP, and batho-phen procedures, decreasing the possibility of interferences due to organics absorbing in the near-UV range of the visible spectrum where most antioxidant assays are performed. The linear concentration ranges were shown to be further extended and linear correlation coefficients improved with respect to the most widely used ferric-based assay, FRAP. Of the six assays tested and developed, only the modified ferricyanide procedure gave high intercept values and low addivitity of TAC values of constituents in complex mixtures, requiring further attention of method optimization. Thus, it was shown that the most widely used FRAP could be effectively modified, and o-phen, batho-phen, and ferricyanide methods constitute cheaper alternatives to FRAP under certain conditions, with partly improved molar absorptivity (and thus sensitivity) for antioxidants, lower intercept values (and higher precision), broader linear range (and higher flexibility), and better additivity of TAC values of antioxidant constituents in mixtures.

Hemi[4-(carboxymethoxy)phenylsulfanylacetato-κ2O,O′]hemi[4-(carboxymethylsulfanyl)phenyloxyacetato]bis(1,10-phenanthroline-κ2N,N′)cadmium(II) 4-(carboxymethoxy)phenylsulfanylacetate dihydrate

The reaction of cadmium nitrate with 4-(carboxy­methoxy)­phenyl­sulfanyl­acetic acid in the presence of phenanthroline at a pH of 6 affords the salt, [Cd(C10H9O5S)(C12H8N2)2](C10H9O5S)·2H2O. The Cd atom in the cation is chelated by two phenanthroline units and one carboxyl­ate from the monoanionic ligand in a distorted octahedral geometry. The coordinated monoanion shows disorder which results in a 50:50 mixture of 4-(carboxy­methoxy)­phenyl­sulfanyl­acetate and 4-(carboxy­methyl­sulfanyl)­phenyl­oxy­acetate coordinated to the cadmium. The cation and uncoordinated anion interact to form a linear chain.

Simultaneous Kinetic Spectrophotometric Determination of Ascorbic Acid and L-Cysteine by H-Point Standard Addition Method

The H-point standard addition method (HPSAM) is applied to kinetic data for the simultaneous determination of ascorbic acid (AA) and L-cysteine (Cys). If present in excess amounts, iron(III) is quantitatively reduced to iron(II) by AA or Cys which in turn, in the presence of phenanthroline (phen), produces a colored iron(II)-phen complex showing maximum absorbance at 510 nm. HPSAM is based on the difference of the reaction rates between AA and Cys with Fe(III). The linear dynamic ranges for the two analytes AA and Cys are 0.50–4.00 ppm and 1.00–8.00 ppm, respectively. The RSD% for 6 replications of AA and Cys at 3.00 ppm is 2.30 and 2.70, respectively. The predictability of the method is checked by determining the two analytes in real samples. The various effects of several similar reducing agents are investigated.

Radical-Like Activation of Alkanes by the Ligated Copper Oxide Cation (Phenanthroline)CuO+

Electrospray ionization mass spectrometry of copper(II) nitrate solution in the presence of phenanthroline (phen) leads to the generation of the monocation (phen)Cu(NO3)+ from which NO2 is lost at ...

Characterization of the Surface Electrode Reaction in the Presence of Uniform Interaction: The Case of Mo(VI) Reduction in the Presence of Phenanthroline and an Excess of Fulvic Acids

AbstractSurface electrode reactions involving lateral uniform interactions between adsorbed species is studied by means of square‐wave voltammetry (SWV). Interactions are represented by the interaction product aΘ, were a is the Frumkin interaction parameter (a is positive for attraction and negative for repulsion forces) and Θ is the surface coverage. The properties of the SW voltammetric response enable detection of interactions and recognition of the type of interaction forces by a simple procedure. The influence of the interactions on the apparent electrochemical reversibility of the surface electrode reaction is studied in detail. Utilizing “quasireversible maximum” the simple methodology for estimation of the standard redox rate constant without knowing the exact value of the interaction product aΘ is developed. Theoretical predictions are illustrated and confirmed by experiments with Mo(VI) in the presence of phenantroline and an excess of fulvic acids.

Facilitated alkali ion transfer at the water|1,2-dichloroethane interphase: ab initio calculations concerning alkaline metal cation–1,10-phenanthroline complexes

Abstract A series of calculations on the energetics of complexation of alkaline metal cations with 1,10-phenanthroline are presented. It is an experimental fact that the ordering of the Gibbs energy of transfer across the water|1,2-dichloroethane interphase is governed by the charge/size ratio of the different cations; the larger cations showing the lower Gibbs energy of transfer. This ordering of the Gibbs energies of transfer is reverted in the presence of 1,10-phenanthroline in the organic phase. We have devised a thermodynamic cycle for the transfer process and, by means of ab initio calculations, have drawn the conclusion that in the presence of phenanthroline the Gibbs energy of transfer is governed by the stability of the phenanthroline/M+ complex, which explains the observed tendency from a theoretical point of view.

Protection of cultured rat gastric cells against oxidant stress by iron chelation

Reactive oxygen metabolites may be involved in the pathogenesis of ethanol-, nonsteroidal antiinflammatory drug-, Helicobacter pylori-, or ischemia/reoxygenation-induced gastric mucosal injury in vivo. Iron plays a critical role in mediating oxidant injury in vitro. The present study examined a possible role of lipid peroxidation in inducing oxidant damage by determining the effect of iron chelation on cytotoxicity and on lipid peroxidation in cultured rat gastric cells. Cytotoxicity was quantified by 51Cr release from prelabeled cells that were exposed to tert-butyl hydroperoxide (tBHP) so as to overwhelm the glutathione redox cycle. Lipid peroxidation was assessed by measuring malondialdehyde (MDA) production. tBHP caused a time-related and dose-dependent increase of 51Cr release. The presence of phenanthroline (a chelator of Fe2+) during tBHP exposure and pretreatment with deferoxamine (a chelator of Fe3+) reduced tBHP-induced 51Cr release dose dependently. The generation of MDA increased as the concentrations of tBHP increased, but in a time course study, such generation preceded cytolysis. Both iron chelators attenuated MDA production in a dose-dependent fashion. Oxidant stress causes lipid peroxidation in cultured gastric cells, which is then followed by cytolysis. Iron plays a critical role in inducing lipid peroxidation as well as in mediating cytolysis. Iron chelation protects these cells from oxidant stress presumably through inhibition of lipid peroxidation.

Reactive oxygen metabolite‐induced toxicity to cultured bovine endothelial cells: Status of cellular iron in mediating injury

We aimed to determine the status of iron in mediating oxidant-induced damage to cultured bovine aortic endothelial cells. Chromium-51-labeled cells were exposed to reaction mixtures of xanthine oxidase/hypoxanthine and glucose oxidase/glucose; these produce superoxide and hydrogen peroxide, or hydrogen peroxide, respectively. Xanthine oxidase caused a dose dependent increase of 51Cr release. Damage was prevented by allopurinol, oxypurinol, and extracellular catalase, but not by superoxide dismutase. Prevention of xanthine oxidase-induced damage by catalase was blocked by an inhibitor of catalase, aminotriazole. Glucose oxidase also caused a dose-dependent increase of 51Ci release. Glucose oxidase-induced injury, which was catalase-inhibitable, was not prevented by extracellular superoxide dismutase. Both addition of and pretreatment with deferoxamine (a chelator of Fe3+) prevented glucose oxidase-induced injury. The presence of phenanthroline (a chelator of divalent Fe2+) prevented glucose oxidase-induced 51Cr release, whereas pretreatment with the agent did not. Apotransferrin (a membrane impermeable iron binding protein) failed to influence damage. Neither deferoxamine nor phenanthroline influenced cellular antioxidant defenses, or inhibited lysis by non-oxidant toxic agents. Treatment with allopurinol and oxypurinol, which inhibited cellular xanthine oxidase, failed to prevent glucose oxidase injury. We conclude that (1) among the oxygen species extracellularly generated by xanthine oxidase/hypoxanthine, hydrogen peroxide induces damage via a reaction on cellular iron; (2) deferoxamine and phenanthroline protect cells by chelating Fe3+ and Fe2+, respectively; and (3) reduction of cellular stored iron (Fe3+) to Fe2+ may be prerequisite for mediation of oxidant-induced injury, but this occurs independently of extracellular superoxide or cellular xanthine oxidase-derived superoxide.

Role of iron and superoxide in mediating hydrogen peroxide injury to cultured rat gastric cells

Background: Gastric epithelium is exposed to toxic, reactive oxygen species generated within the lumen. The present study examined the role of cellular iron and superoxide (O2−) in mediating hydrogen peroxide (H2O2)-induced damage to cultured gastric mucosal cells. Methods: H2O2 was generated by glucose oxidase acting on b-d(+)glucose. Cytotoxicity was assessed by 51Cr release from prelabeled cells. Results: Deferoxamine (a chelator of Fe3+) prevented injury induced by H2O2, whether present before or during H2O2 production. In contrast, whereas the presence of phenanthroline (a chelator of Fe2+) during the cytotoxicity assay prevented damage, prior treatment with the agent did not; this suggested that cellular Fe3+ reduced to Fe2+ upon exposure to H2O2 is responsible for damage. Neither extracellular superoxide dismutase nor inhibitors of xanthine oxidase (a possible source of cellular O2− production) protected against H2O2. Further, protection by iron chelators was not associated with modulation of endogenous antioxidants. Conclusions: Deferoxamine and phenanthroline protect cells from H2O2 by chelating stored iron (Fe3+) or reduced iron (Fe2+), respectively. Reduction of cellular Fe3+ appears to be a prerequisite for mediation of damage, but this reduction is independent of extracellular O2− or cellular xanthine oxidase-derived O2−.

Fluorescence enhancement of terbium(III) by nucleotides and polyhomonucleotides in the presence of phenanthroline

The fluorescence enhancement of terbium(III) by nucleotides (AMP, ADP, ATP, GMP, GDP, GTP) and polyhomonucleotides [poly(A), poly(G), poly(C), poly(U)] in the presence of phenanthroline (phen) was studied. Investigation of the composition of the terbium(III)/ANP(AMP, ADP, ATP)/phen complexes and conditions of optimization suggest a 1:2 molar ratio of terbium(III) and phen for the ternary complexes. The results showed that the presence of phen enhanced the net fluorescence of terbium(III)/ANP, poly(A), poly(C) or poly(U) from several fold to more than one-hundred fold, while it has little effect on the fluorescence of terbium(III)/GNP(GMP, GDP and GTP) or the poly(G) system. The possibility of spectrofluorimetric measurements of these compounds were studied under optimal conditions (pH 7.0 in tris-HCl buffer; Ex=298 nm, Em=543.5 nm). The detection limits were 2.0×10−7, 6.0×10−7 and 1.0×10−6 mol/l for AMP, ADP and ATP, respectively. The relative standard deviations (6 replicates) were within 2.0% in the middle of the linear range.

Fluorescence reaction of terbium(III) with nucleic acids in the presence of phenanthroline

The fluorescence enhancement reaction of terbium(III) with DNA or RNA in the presence and absence of phenanthroline (Phen) was studied. Studies involving natural and denatured calf thymus DNA, fish sperm DNA and yeast RNA revealed that the presence of phen enhanced the net fluorescence 3–12-fold. The results suggest a 1 : 2 molar ratio of terbium(III) and phen for the ternary complex. Maximum fluorescence was produced in the pH range 6.8–7.2. The calibration graphs was linear between 0.4 and 15.0 or 20.0 μg ml −1 for thermally denatured nucleic acids and the detection limits were 0.1–0.2 μg ml −1. The relative standard deviation (six replicates) was within 3.0% in the linear range. Yeast RNA could be determined in the presence of up to 40% calf thymus DNA and the latter was determined when the content of yeast RNA in synthetic samples was below 10%.

ChemInform Abstract: Direct Observation of η2-Arene Complexes of ((C5Me5)Rh(PMe3)).

The aryl hydride complex (I) is well established to lose benzene upon heating to 60 °C. However, in the presence of phenanthroline (II) the η2-arene complex (III) (space group P21/c, Z=4) is formed.