Carboxamide Complexes Research Articles

Investigating the Replacement of Carboxylates with Carboxamides to Modulate the Safety and Efficacy of Platinum(II) Thioether Cyanide Scavengers.

Cyanide represents a persistent threat for accidental or malicious misuse due to easy conversion into a toxic gas and access to large quantities through several industries. The high safety index of hydroxocobalamin is a cornerstone quality as a cyanide scavenger. Unfortunately, intravenous infusion of hydroxocobalamin limits the utility in a mass casualty setting. We previously reported platinum(II) [Pt(II)] complexes with trans-directing sulfur ligands as an efficacious alternative to hydroxocobalamin when delivered by a bolus intramuscular injection in mice and rabbits. Thus, to enable Pt(II) as an alternative to hydroxocobalamin, a high safety factor is needed. The objective is to maintain efficacy and mitigate the risk for nephrotoxicity. Platinum amino acid complexes with the ability to form five- or six-membered rings and possessing either carboxylates or carboxamides are evaluated in vitro for cyanide scavenging. In vivo efficacy was evaulated in the zebrafish and mice cyanide exposure models. In addition, Pt(II) complex toxicity and pharmacokinetics were evaluated in a cyanide naive Sprague-Dawley model. Doses for toxicity are escalated to 5x from the efficacious dose in mice using a body surface area adjustment. The results show the carboxamide ligands display a time and pH dependence on cyanide scavenging in vitro and efficacy in vivo. Additionally, exchanging the carboxylate for carboxamide showed reduced indications of renal injury. A pharmacokinetic analysis of the larger bidentate complexes displayed rapid absorption by intramuscular administration and having similar plasma exposure. These findings point to the importance of pH and ligand structures for methionine carboxamide complexes with Pt(II).

Carboxamide Fe(III) complex as the electrocatalyst of water oxidation reaction: WNA and I2M O–O bond formation pathways

A single-site Fe(III) carboxamide complex, [Fe(HbpH) (Cl)2] (1), (HbpH‾ = N,N′-Bis(picolinoyl)hydrazine) anion), was synthesized and used as the electrocatalyst of water oxidation reaction. Complex 1 catalyzes the oxidation of water to O2 at the pH of 8 in phosphate buffer solution with the onset of a catalytic wave at about 0.45 V versus RHE with the turnover frequency (TOF) of 5.8 s−1 at room temperature. The stability of the catalyst in water oxidation processes by electrochemical and UV–vis measurements, demonstrated the realistic molecular electrocatalysis of 1. Differential pulse voltammetry (DPV) of 1 in different pH values showed the dependency of oxidation potential to the pH of the environment, establishing the fact that the catalytic cycle involves the proton-coupled electron transfer (PCET) process. Density functional theory (DFT) calculations on the mechanism of water oxidation process of 1 shows that the oxygen evolution reaction is carried out through the water nucleophilic attack (WNA) to the metal center ion, resulted to the formation of FeIV(O) species. Also, DFT calculations showed that the formation of an O–O bond proceeds through the interaction two molecular mechanism (I2M), which compete with the WNA mechanism following from experimental analysis. The electroactivity of the metal centre and carboxamide ligand and the ability of the ligand to stabilize the high oxidation numbers of the metal-ion centre during the oxidation process, provide different oxidation pathways for an OER process.

Exploring the coordination of peptide bonds towards beryllium with carboxamides, esters and ketones

AbstractTwo carboxamide complexes of BeCl2 with NH functions have been prepared and structurally characterized. Bis(2‐pyrrolidone) beryllium(II) chloride and bis(N‐phenyl acetamide) beryllium(II) chloride show extensive hydrogen bond networks in the solid state, which leads to low solubility in organic solvents. Related complexes bis(phenyl acetate) beryllium(II) chloride and bis(acetophenone) beryllium(II) chloride have also been prepared and structurally characterized. These lack hydrogen bonds in the solid state and are therefore highly soluble in chlorinated solvents.

Co(III) carboxamide complexes as electrocatalysts for water splitting

Water splitting is a promising approach for storing intermittent renewable energies, such as sunlight in the clean chemical bonds as a hydrogen fuel. Two water-soluble octahedral cobalt (III) complexes, [Co(bpb)(OAc)(H2O)], 1, (bpb2− = N,N′-bis[(2-pyridine carboxamide)-1,2-benzene] dianion) and [Co(cbpb)(OAc)(H2O)], 2, (cbpb2− = N,N′-bis[(2-pyridine carboxamide)-4-chloro-1,2-benzene] dianion) were synthesised and characterised by CHN elemental analysis, UV–Vis, FT-IR and single-crystal X-ray diffraction techniques. The two carboxamide ligands had been prepared in the ionic liquid TBAB as an environmentally benign reaction medium. The electrocatalytic water splitting activity of 1 and 2 showed that both complexes are highly active for the water splitting in aqueous solutions. Turn Over Frequency (TOF) values were, for 1 and 2 respectively, 527 and 490 mol of hydrogen in each mole of catalyst per hour at an overpotential of 738 mV (pH = 7.0). Such a performance can be ascribed to the flat ligands, the electroactivity of the metal centre and carboxamide ligands and the ability of losing the axial ligands around the metal-ion centre during the reduction process which provide different reduction pathways for an HER process.

New Volatile Tantalum Imido Precursors with Carboxamide Ligands.

A series of Ta(V) tBu-imido/N-alkoxy carboxamide complexes, TaCl2(NtBu)(pyridine)(edpa) (1), TaCl(NtBu)(edpa)2 (2), Ta(NtBu)(edpa)3 (3), TaCl2(NtBu)(pyridine)(mdpa) (4), and Ta(NtBu)(mdpa)3 (5), were successfully synthesized by metathesis reactions between Ta(NtBu)Cl3(py)2 and several equivalents of Na(edpa) (edpaH = N-ethoxy-2,2-dimethylpropanamide) and Na(mdpa) (mdpaH = N-methoxy-2,2-dimethylpropanamide). Furthermore, complexes 3 and 5 were simply transformed to new dimeric structures [Ta(μ2–O)(edpa)3]2 (6) and [Ta(μ2–O)(mdpa)3]2 (7) with the elimination of the NtBu imido group by air exposure. Compounds 1–7 were characterized by 1H and 13C nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis (TGA), and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis revealed that complexes 3 and 5 have a distorted pentagonal bipyramidal geometry around the central Ta atom, with three monoanionic bidentate N-alkoxy carboxamide ligands and one tBu imido ligand saturating the coordination of tantalum ions. TGA revealed that complexes 3 and 5 had superior thermal characteristics and stability. These complexes could potentially be applied as precursors for tantalum oxide thin films.

Synthesis of novel volatile niobium precursors containing carboxamide for Nb2O5 thin films

A series of novel Nb(V) tBu-imido/N-alkoxy carboxamide complexes, NbCl2(NtBu)(pyridine)(edpa) (1), NbCl2(NtBu)(pyridine)(mdpa) (2), and Nb(NtBu)(mdpa)3 (3), were successfully synthesized by metathesis reaction between Nb(NtBu)Cl3(py)2 and several equivalents of Na(edpa) (edpaH = Nethoxy-2,2-dimethylpropanamide) and Na(mdpa) (mdpaH = N-methoxy-2,2-dimethylpropanamide). These complexes could potentially serve as precursors for Nb-containing thin films. Compounds 1–3 were characterized by FT-IR and 1H and 13C NMR spectroscopies, elemental analysis, and thermogravimetric analysis (TGA). Single crystal X-ray diffraction analysis suggested that complex 3 has a distorted pentagonal bipyramidal geometry around the central Nb atom, with three bidentate mdpa ligands and one tBu imido group saturating the coordination. TGA analysis revealed that the thermal characteristics of 3 were superior to those of 1 and 2. All prepared complexes were able to be distilled or sublimed and expected potential precursors for the fabrication of thin films.

A nickel nanoparticle engineered CoFe2O4/SiO2-NH2@carboxamide composite as a novel scaffold for the oxidation of sulfides and oxidative coupling of thiols.

The purpose of this work was to prepare a new Ni–carboxamide complex supported on CoFe2O4 nanoparticles (CoFe2O4/SiO2–NH2@carboxamide–Ni). The carboxamide host material unit generated cavities that stabilized the nickel nanoparticles effectively and prevented the aggregation and separation of these particles on the surface. This compound was appropriately characterized using FT-IR spectroscopy, FE-SEM, ICP-OES, EDX, XRD, TGA analysis, VSM, and X-ray atomic mapping. The catalytic oxidation of sulfides and oxidative coupling of thiols in the presence of the designed catalyst was explored as a highly selective catalyst using hydrogen peroxide (H2O2) as a green oxidant. The easy separation, simple workup, excellent stability of the nanocatalyst, short reaction times, non-explosive materials as well as appropriate yields of the products are some outstanding advantages of this protocol.

Promising new catalytic properties of a Co (II)‐carboxamide complex and its derived Co3O4 nanoparticles for the Mizoroki‐Heck and the Epoxidation reactions

The new Co(II) ‐ carboxamide complex (1) and Co3O4 nanoparticles (2), by way of thermal decomposition of (1) have been efficiently synthesised in the environment‐friendly. X‐ray diffraction reveals a slightly distorted octahedral coordination of cobalt (four nitrogens and two oxygens) in (1) and regular octahedral or tetrahedral ones (oxygens only) in (2). The investigation of (1) and (2) in the Mizoroki‐Heck and epoxidation of alkens reactions showed them both to be powerful, green and inexpensive catalysts.

Synthesis, X-ray characterization and catalytic homogenous alcohol oxidation activity of Co(II)–carboxamide complex with green oxidant (H2O2) under mild conditions

Abstract In this study, a new air and moisture stable mononuclear cobalt(II)–carboxamide complex, [Co(TCrbx)2(CH3OH)2](ClO4)2, was synthesized and characterized (TCrbx = N-(4-methylpyridin-2-yl)thiophene-2-carboxamide). Complex characterization mainly was done with single crystal X-ray analysis. Ligand characterization was done with several spectroscopic techniques (Elemental Analysis, FT-IR, 1H NMR, 13C NMR). Cobalt(II) complex possesses distorted octahedral geometry coordinated with two carboxamide ligands at equatorial and two methanol ligands at axial positions and two perchlorate anions as counter ions. Synthesized complex was successfully tested as homogenous catalyst for the oxidation of benzyl alcohol with environmental friendly oxidant hydrogen peroxide (H2O2) under mild conditions. Benzaldehyde was selectively obtained with the conversion value of 99.5% in dimethyl formamide after 3-h reaction time at 50 °C with 133 TON value. Solvent and temperature effects were also investigated.

Synthesis, Characterisation and Crystal structure of a New Cu(II)-carboxamide Complex and CuO nanoparticles as New Catalysts in the CuAAC reaction and Investigation of their Antibacterial activity

The bidentate carboxamide ligand N-(thiazole-2-yl) picolinamide (LH) was synthesized in the environmentally friendly ionic liquid TBAB, and the five-coordinated CuII-complex, [Cu(L)2(H2O)].CHCl3(1) was synthesized from LH and copper(II)acetate. Cupric oxide [CuO] nanoparticles (2) have been prepared by the thermal decomposition of (1) as a new precursor at 600 °C for 3 h under air atmosphere. (1) was characterised using FT-IR spectroscopy, elemental analyses and its solid state structure was confirmed by single crystal X-ray diffraction. (2) were identified by FT-IR spectroscopy, X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray analysis and thermo-gravimetric differential thermal analyses. The electrochemical behaviour of LH and (1) has been investigated by cyclic voltammetry: irreversible CuII/I reductions were observed. The catalytic activity of (1) and (2) were evaluated in the one-pot azide–alkyne cycloaddition click reaction in water without additional agents. LH, (1) and (2) were also screened for their in vitro antibacterial activity: they showed promising antibacterial activity comparable to that of the antibiotic penicillin.

A series of new pyridine carboxamide complexes and self-assemblies with Tb(III), Eu(III), Zn(II), Cu(II) ions and their luminescent and magnetic properties

In this study, we present eight new complexes and self-assemblies of Tb(III), Eu(III), Zn(II) and Cu(II) ions with novel pyridine carboxamides, L1 [methyl 4-methyl-3-(pyridine-4-carbonylamino)benzoate] and L2 [methyl 2-methyl-3-(pyridine-4-carbonylamino)benzoate], as heterocyclic ligands. Two luminescent and spatially organized coordination compounds were obtained with the use of the solvothermal synthesis method, (1) [Tb3(L1)4(BTC)3(H2O)3] (where BTC is benzene-1,3,5-tricarboxylic acid) and (5) [Eu(L2a)3(H2O)3](H2O)4. As a result of one pot reaction synthesis under reflux the d-electron metal ions and self-organization of ligands gave complexes (2) [Zn(L1)2Cl2], (3) [Cu(L1)2(SCN)2(H2O)], (4) [Cu(L1)2Cl2], hybrid salt (6) [(CuCl4)2-(L2b)22+](H2O), (7) [Cu(L2)2Cl2] and 1D-chain coordination polymer (8) [Cu(L2)2(SCN)2]. Identification of the obtained compounds was performed on the basis of the excitation, emission, 1H NMR, FT-IR spectra, luminescence lifetimes, SEM images, PXRD, single-crystal X-ray diffraction, MS, TGA and elemental analysis. Selected compounds were also analyzed in terms of their potential magnetic properties.

Small molecule activation of nitriles coordinated to the [Re6Se8]2+ core: formation of oxazine, oxazoline and carboxamide complexes.

Novel oxazine, oxazoline and carboxamide cluster complexes were prepared when different nucleophilic oxygen species reacted with nitriles coordinated to the Lewis acidic [Re6Se8]2+ cluster core. Reaction of ICH2CH2O- (generated in situ) with [Re6Se8(PEt3)5(NCR)]A2 (1A2 (R = Me) and 2A2 (R = Ph) where A = BF4-), leads to the formation of [Re6Se8(PEt3)5(2-methyloxazoline)]2+ (32+) and [Re6Se8(PEt3)5(2-phenyloxazoline)]2+ (42+). Similarly, reaction of BrCH2CH2CH2O- with the same nitrile complexes, 1A2 and 2A2 (where A = BF4- or SbF6-) leads to the corresponding oxazine complexes, [Re6Se8(PEt3)5(2-methyloxazine)]2+ (52+) and [Re6Se8(PEt3)5(2-phenyloxazine)]2+ (62+). In addition, reaction of 2(BF4)2 with KOH leads to the formation of the carboxamide complex, [Re6Se8(PEt3)5(phenylcarboxamide)](BF4) (7(BF4)). The neutral oxazine and oxazoline ligands can be removed using either heat or UV irradiation; UV irradiation was found to be more efficient at ligand removal as indicated by the shorter reaction times. The relative coordination strength of the neutral N-donor ligands was determined by these reaction times. X-ray structure determinations of 5(BF4)2 and 7(BF4) are also reported.

Facile Synthesis of Cobalt Oxide Nanoparticles by Thermal Decomposition of Cobalt(II) Carboxamide Complexes: Application as Oxygen Evolution Reaction Electrocatalyst in Alkaline Water Electrolysis

Cobalt oxide nanoparticles, Co3O4 (1) and Co3O4 (2), have been synthesized by thermal decomposition of [CoII(bqbenzo)] and [CoII(bqb)], respectively. The morphology of these oxides is influenced by the difference in the structure of bqbenzo2− {3,4-bis(2-quinolinecarboxamido) benzophenone and, bqb2− {bis(2-quinolinecarboxamido)-1,2-benzen}, only differing in a benzoyl substituent. The products were characterized by XRD, FE-SEM, and FT-IR spectroscopy. The catalytic activity of the oxides was examined in oxygen evolution reaction (OER) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The Co3O4 oxides (1 and 2) exhibited higher catalytic activity compared to 10 wt% Pt/C in terms of obtained current density at 0.8 V; ∼23.3 versus 6.1 mA cm−2, respectively. However, the aging tests of the two oxides in OER revealed that Co3O4 (1) is more stable than Co3O4 (2). These results demonstrated that the Co3O4 (1) has a superior performance which can be employed in the alkaline water electrolyzer anode.

Synthesis, crystal structure and electrochemistry of cobalt(III) carboxamide complexes with amine and azide ancillary ligands

Six cobalt(III) complexes of the type [CoIII(Me2bpb)(amine)(N3)] {Me2bpb2−=N,N′-(4,5-dimethyl-1,2-phenylene)dipicolinamide and amine=piperidine (pprdn) (1), pyrrolidine (prldn) (2), morpholine (mrpln) (3), pyridine (py) (4), 4-methylpyridine(4-Mepy) (5) and 4-acetylpyridine (4-Acpy) (6)} have been synthesized and characterized by elemental analyses, IR and UV–Vis spectroscopy. The structures of 1, 3 and 4 have been determined by X-ray crystallography. Me2bpb2− is a dianionic tetradentate ligand, furnishing a N4 set, such that two N atoms of the two pyridine rings and two amido N atoms occupy four equatorial positions. The amine and azide ligands occupy the two axial positions, leading to a distorted octahedral geometry around the central cobalt ion. The electrochemical behavior of these complexes in DMF solution indicates that partial solvolysis of the complexes occurs and the axial amine ligand is replaced by DMF solvent in 1–6 leading to a [CoIII(Me2bpb)(DMF)(N3)] species. The two additional redox processes observed in the cyclic voltammograms of these complexes originate from the oxidation of the 4,5-dimethylorthophenylene moiety of the Me2bpb2− ligand and a CoIII/II redox process in [CoIII(Me2bpb)(DMF)(N3)]. The CoIII/II redox potential of the [CoIII(Me2bpb)(amine)(N3)] complexes is influenced by the nature of the axial amine ligand and varies from −0.53 for 4-Acpy to −0.79V for pyrrolidine.

Synthesis, characterization, and antibacterial activity of the ligands including thiophene/furan ring systems and their Cu(II), Zn(II) complexes

Carboxamide complexes having general formula as [ML]Cl2·nH2O (where M = Cu(II), Zn(II); n = 0, 1/2) were synthesized using heterocyclic carboxamide ligands: 1,4-bis[3-(2-thiophenecarboxamido)propyl]piperazine (L1) and 1,4-bis[3-(2-furancarboxamido) propyl]piperazine (L2). Their structures were characterized with elemental analysis, molar conductivity, magnetic susceptibility, and spectral methods (1H-NMR, 13C-NMR, FT-IR, LC-MS). TGA and DTA curves were also performed. The structure–activity relationship for the ligands was investigated using PM3 semi-empirical method. The antibacterial activities of the carboxamides and their complexes were investigated against bacteria; Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 11230, Bacillus magaterium RSKK 5117, B. cereus RSKK 863, Salmonella enteritidis ATCC 13076, B. subtilis RSKK 244 using microdilution method.

Synthesis, crystal structure, DNA-binding and cytotoxicity in vitro of novel cis-Pt(II) and trans-Pd(II) pyridine carboxamide complexes

In an attempt to establish fundamental structure-activity relationships (SAR) of Pt/Pd-based anti-tumour compounds, we have recently designed monodentate pyridyl amide ligand containing central amide units which possess external metal co-ordinating pyridyl group and internal amide functionality. It was prepared in one step from commercially available compounds in moderate to good yield. Surprisingly, treatment of K(2)[MCl(4)] [M=Pt(II), Pd(II)] with ligand N-(4-chlorophenyl)-3-pyridinecarboxamide (L) in the same reaction condition affords two different hydrogen-bonded polymers: cis-[PtL(2)Cl(2)]·CH(3)OH·DMF (1) and trans-[PdL(2)Cl(2)]·2DMF (2). Fluorescence analysis indicates that the two complexes can bind to fish sperm DNA (FS-DNA) and gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR322 plasmid DNA. The two complexes exhibit cytotoxic specificity and significant cancer cell inhibitory rate. Furthermore, cytotoxicity values are higher in the case of cis-Pt(II) complex than trans-Pd(II) complex in four different cancer cell lines.

Copper(II) and zinc(II) complexes of thiophene/furan carboxamides: Synthesis, structure and properties

Cu(II) and Zn(II) complexes were synthesized from equimolar amounts of carboxamides; 1,8-bis(2-thiophenecarboxamido)-p-menthane (tkdam) and 1,8-bis(2-furancarboxamido)-p-menthane (furdam). The structure of the carboxamides were determined by elemental analysis; 1H NMR, 13C NMR, FT-IR and LC-MS spectra. The relative energies and the electronic properties (LUMO, HOMO, LUMO-HOMO gap) of the ligands were investigated theoretically by performing Semi-empirical molecular orbital theory PM3 method in Hyperchem 7 (Release). Carboxamide complexes having general formula as; monomeric, [ML]Cl2 and dimeric [Cu(tkdam)Cl]2Cl2 · 5H2O were synthesized and characterized by using element analysis; FT-IR, LC-MS spectra; magnetic susceptibility, molar conductivity and thermal (TGA/DTA curve) studies. It was found that the coordination number of the monomeric complexes is four whereas dimeric’s is six. The changes in the selected vibration bands in FT-IR indicate that, carboxamides behave as tetradentate ligands and coordinate to metal ions from acyl ring (through S/O) and amide carbonyl (C=O). Molar conductivity measurements indicate the 1: 2 ionic nature of the carboxamide complexes.

Highly Efficient Isobutyraldehyde-Mediated Epoxidation of Cyclic Alkenes with Dioxygen Catalyzed by a Novel Dimeric Manganese(II) Complex Containing an Easy-to-Prepare Flexible Carboxamide Ligand

Dioxygen epoxidation of cyclic alkenes into their corresponding epoxides was successfully achieved in good yield by using a novel binuclear manganese carboxamide complex as the catalyst and isobutyraldehyde as the cosubstrate.

Structural effects on electrochemical properties of the carboxamide complexes [Ni II(Mebpb)] and [Ni II(Mebqb)

Two Ni(II) complexes of the dianionic ligands, Mebpb 2−, [H 2Mebpb = N, N′-bis(pyridine-2-carboxamido)-4-methylbenzene] and Mebqb 2−, [H 2Mebqb = N, N′-bis(quinoline-2-carboxamido)-4-methylbenzene] have been synthesized and characterized by elemental analyses, IR, and UV–Vis spectroscopy. The crystal and molecular structures of [Ni(Mebpb)], ( 1), and [Ni(Mebqb)], ( 2), were determined by X-ray crystallography. Both complexes exhibit distorted square–planar NiN 4 coordination figures with two short and two long Ni–N bonds (Ni–N ∼1.84 and ∼1.95 Å, respectively). The electrochemical behavior of these complexes with the goal of evaluating the structural effects on the redox properties has been studied.

The first example of ligand-mediated dehydration of aldoximes

The nitrile complex trans-[PtCl 4(EtCN) 2] reacts with the aldoximes HONC(H)R [R=C(Ph)(O), Me, Ph] in CH 2Cl 2 to afford products of the addition of the aldoxime HON group across the nitrile CN triple bond, i.e. trans-[PtCl 4{NHC(Et)ONC(H)R} 2] ( 1– 3). These compounds were characterized by elemental analyses, FAB MS, IR and 1H and 13C{ 1H} spectroscopies and X-ray structure determination has been performed for 1. In CHCl 3 solution, 1– 3 undergo the spontaneous imine ligand splitting to achieve the carboxamide complex trans-[PtCl 4{NHC(Et)OH} 2] and RCN thus giving the first example of a ligand-mediated dehydration of aldoximes. The carboxamide and RCN products are also formed upon treatment of trans-[PtCl 4(EtCN) 2] with 2 equiv. of HONC(H)R in CH 2Cl 2.