Oxalato Complexes Research Articles

Molecular Structure, Spectroscopic, Frontier Molecular Orbital Analysis, Molecular Docking Studies, and In Vitro DNA-Binding Studies of Osmium(II)-Cymene Complexes with Aryl Phosphine and Aryl Phosphonium Assemblies.

X-ray crystallography, spectroscopy, computational methods, molecular docking studies, and in vitro DNA-binding studies have been useful in the investigations of intermolecular and intramolecular interactions of osmium-cymene oxalato complexes with aryl phosphine and aryl phosphonium groups in both primary and secondary coordination spheres, respectively. Molecular structures of the novel complexes PPh4[Os(η6-p-cymene)Br(κ2-O,O'-C2O4)] (1) and [Os(η6-p-cymene) (κ2-O,O'-C2O4)PPh3] (2) were resolved by single-crystal X-ray diffraction (XRD). Primary and secondary coordination sphere contacts were investigated using Hirshfeld surface analysis which was supported by molecular docking (MD) studies. The MD data obtained predicted significant differences in binding energy across three receptors for the two osmium complexes. An in vitro DNA-binding study was accomplished using UV-Vis spectroscopy which showed that both 1 and 2 bond with DNA through an intercalation approach. The optimized molecular geometry, frontier molecular orbital (EHOMO and ELUMO) energies, global electrophilicity index (ω), chemical hardness (η), chemical potential (µ), and the energy band gap (EHOMO-ELUMO) were calculated utilizing density functional theory (DFT) methods. Computed structural parameters (bond lengths and angles) support the experimental single-crystal XRD data.

Synthesis, characterization and in vitro cytotoxic activity of platinum(II) oxalato complexes involving 2-substitutedimidazole or 2-substitutedbenzimidazole derivatives as carrier ligands

Synthesis, characterization and in vitro cytotoxic activity of platinum(II) oxalato complexes involving 2-substitutedimidazole or 2-substitutedbenzimidazole derivatives as carrier ligands

Ruthenium arene complexes with chalcone ligands incorporating pyridyl and anthryl units: Synthesis, aqueous stability and interaction with quadruplex DNA

Twelve ruthenium(II) arene complexes incorporating chalcone ligands with pyridyl and anthryl units, as well as chlorido or oxalato ancillary ligands, have been synthesized and structurally characterized by 1H NMR spectroscopy, ESI mass spectrometry and elemental analysis. Compared to the oxalato compounds, the chlorido complexes were less stable and more susceptible to aquation in solution; the dissociation was suppressed in the presence of chloride ions. All six of the chlorido complexes and three of the oxalato complexes were able to bind to quadruplex DNA, exhibiting greater selectivity for HTelo over c-myc. The cationic species 3f, in which the chalcone chelates to the metal center, was found to bind to HTelo most strongly. These results indicate that the ancillary ligand, the location of the N-donor atom in the pyridyl ring, the position of the α,β-unsaturated ketone relative to the pyridyl and anthryl entities in the chalcone moiety, as well as the presence of the metal center all play significant roles in improving the binding of such complexes to quadruplex DNA.

Exciton Coupling in Redox-Active Salen based Self-Assembled Metallacycles.

The incorporation of a redox-active nickel salen complex into supramolecular structures was explored via coordination-driven self-assembly with homobimetallic ruthenium complexes (bridged by oxalato or 5,8-dihydroxy-1,4-naphthoquinato ligands). The self-assembly resulted in the formation of a discrete rectangle using the oxalato complex and either a rectangle or a catenane employing the larger naphthoquinonato complex. The formation of the interlocked self-assembly was determined to be solvent and concentration dependent. The electronic structure and stability of the oxidized metallacycles was probed using electrochemical experiments, UV-Vis-NIR absorption, EPR spectroscopy and DFT calculations, confirming ligand radical formation. Exciton coupling of the intense near-infrared (NIR) ligand radical intervalence charge transfer (IVCT) bands provided further confirmation of the geometric and electronic structures in solution.

Spin‐Controlled Binding of Carbon Dioxide by an Iron Center: Insights from Ultrafast Mid‐Infrared Spectroscopy

AbstractThe influence of the spin on the mode of binding between carbon dioxide (CO2) and a transition‐metal (TM) center is an entirely open question. Herein, we use an iron(III) oxalato complex with nearly vanishing doublet–sextet gap, and its ultrafast photolysis, to generate TM‐CO2 bonding patterns and determine their structure in situ by femtosecond mid‐infrared spectroscopy. The formation of the nascent TM‐CO2 species according to [L4FeIII(C2O4)]+ + hν → [L4Fe(CO2)]+ + CO2, with L4=cyclam, is evidenced by the coincident appearance of the characteristic asymmetric stretching absorption of the CO2‐ligand between 1600 cm−1 and 1800 cm−1 and that of the free CO2‐co‐fragment near 2337 cm−1. On the high‐spin surface (S=5/2), the product complex features a bent carbon dioxide radical anion ligand that is O‐“end‐on”‐bound to the metal. In contrast, on the intermediate‐spin and low‐spin surfaces, the product exhibits a “side‐on”‐bound, bent carbon dioxide ligand that has either a partial open‐shell (for S=3/2) or fully closed‐shell character (for S=1/2).

Spin-Controlled Binding of Carbon Dioxide by an Iron Center: Insights from Ultrafast Mid-Infrared Spectroscopy.

The influence of the spin on the mode of binding between carbon dioxide (CO2) and a transition‐metal (TM) center is an entirely open question. Herein, we use an iron(III) oxalato complex with nearly vanishing doublet–sextet gap, and its ultrafast photolysis, to generate TM‐CO2 bonding patterns and determine their structure in situ by femtosecond mid‐infrared spectroscopy. The formation of the nascent TM‐CO2 species according to [L4FeIII(C2O4)]+ + hν → [L4Fe(CO2)]+ + CO2, with L4=cyclam, is evidenced by the coincident appearance of the characteristic asymmetric stretching absorption of the CO2‐ligand between 1600 cm−1 and 1800 cm−1 and that of the free CO2‐co‐fragment near 2337 cm−1. On the high‐spin surface (S=5/2), the product complex features a bent carbon dioxide radical anion ligand that is O‐“end‐on”‐bound to the metal. In contrast, on the intermediate‐spin and low‐spin surfaces, the product exhibits a “side‐on”‐bound, bent carbon dioxide ligand that has either a partial open‐shell (for S=3/2) or fully closed‐shell character (for S=1/2).

Platinum(II)-oxalato complexes of seliciclib (CYC202) derivatives show different cellular effects and lesser adverse effects in mouse lymphoma model than cisplatin.

This work presents a deeper pharmacological evaluation of two formerly prepared and characterized, and highly in vitro cytotoxic platinum(II) oxalato complexes [Pt(ox)(L1)2] (1) and [Pt(ox)(L2)2] (2), containing the derivatives of cyclin-dependent kinase inhibitor (CDKi) seliciclib ((R)-roscovitine, CYC202) coordinating as N-donor carrier ligands, i.e., 2-(1-ethyl-2-hydroxyethylamino)-N6-(4-methoxybenzyl)-9-isopropyladenine (L1) and 2-chloro-N6-(2,4-dimethoxybenzyl)-9-isopropyladenine (L2). The positive results of in vitro cytotoxicity screening on human cancer cell lines (HeLa, HOS, A2780, A2780R, G361 and MCF7 with IC50 at low micromolar levels) published previously, motivated us to perform extended preclinical in vitro experiments to reveal the mechanisms associated with the induction of cancer cell death. In addition, the in vivo antitumor activity was evaluated using the mouse lymphocytic leukaemia L1210 model. The obtained results revealed that complex 1 exceeds the antitumor effect of cisplatin (as for the extension of life-span of mice) and shows far less adverse effects as compared to reference drug cisplatin. The in vitro and ex vivo studies of cellular effects and molecular mechanisms of cell death induction showed that the mechanism of action of complex 1 is essentially different from that of cisplatin. The obtained results showed a possible way how to obtain antitumor active platinum(II) oxalato complexes with better therapeutic profile than contemporary used platinum-based therapeutics.

Supramolecular architectures of metal-oxalato coordination polymers bearing N-tethered adenine nucleobases

Reactions of N-methylated adenine (9-methyladenine and 3-methyladenine) with water-soluble oxalato complexes in the presence of potassium oxalate yields a series of oxalato-bridged complexes with the nucleobases as pendant ligands whose crystal structures and magnetic properties are reported herein. The complexes [M2(µ-ox)2(9Meade)3]n [M(II) = Zn (1), Cu (2); where ox = oxalato and 9Meade = 9-methyladenine] are composed of infinite corrugated one-dimensional chains in which two types of metal(II) centres are sequentially bridged by asymmetric bis-bidentate oxalato ligands and their coordination polyhedra are filled by N7-coordinated 9-methyladenine molecules giving rise to two different chromophores: an octahedral N2O4 donor set with the nucleobase moieties in trans-arrangement, and square based pyramidal NO4 coordination polyhedra. The cohesiveness of their supramolecular 3D architectures is achieved by means of an extensive network of non-covalent interactions including a short contact between the minor groove N3 site of the model 9-methyladenine and the oxalato bridging ligand from a neighbouring chain. This unconventional interaction between the lone pair of the pyrimidinic nitrogen atom of the nucleobase and the π-system of the oxalate anion has been analysed and discussed in the light of available structural data for analogous systems. The compounds {[M(µ-ox)(H2O)(3Meade)]·H2O}n [M(II) = Zn (3), Co (4) and Mn (5); where 3Meade = 3-methyladenine], and {[Cu(µ-ox)(3Meade)2]·4H2O}n (6) are comprised of zig–zag metal-oxalato chains, with the oxalato adopting a symmetric bis-bidentate coordination mode. The octahedral environment of the metals is completed in a cis-arrangement by one water molecule and the imidazole N7 donor site of a 3-methyladenine ligand for 3–5, and by two N7-coordinated nucleobases for 6. The crystal packing of the chains leads to the presence of channels with dimensions of 5 × 10 Å for 6, and 4 × 6 Å for 3–5 which are occupied by crystallization water molecules. The non-covalent interactions of the nucleobases among them and with the metal-oxalato framework have been studied in detail as well as the magnetic interactions mediated by the bridging oxalato ligand.

Oxalato complexes of Pd(II) with Co(II) and Ni(II) as single-source precursors for bimetallic nanoalloys

The single-source precursors of noble–ignoble nanoalloys are of a great interest since they can be used in many areas such as optical, biomedical, catalysis, magnetic and chemosensors. The new water-soluble double complex salts (DCSs) with aqua and oxalato ligands, [M(H2O)6][Pd(Ox)2]·nH2O (M = Co2+, Ni2+; n = 2, 4; Ox = C2O 4 2− ), were obtained, structurally characterized (single-crystal XRD) and used as precursors for M–Pd nanoalloys. Complexes, intermediate and final thermolysis products were studied by simultaneous thermogravimetric analysis combined with mass spectrometry, powder XRD, in situ synchrotron powder XRD, IR and X-ray photoelectron spectroscopy. Decomposition in different atmospheres leads to formation of bimetallic solid solution M0.5Pd0.5 (He, H2) or a mixture of metal oxides (O2). The catalysts M–Pd/TiO2 (1% Pd) were prepared by the decomposition of DCSs deposited onto titania via wetness impregnation. The H2-made Ni-containing samples showed a high photocatalytic activity in CO oxidation reaction.

Synthesis, Characterization, Cytotoxicity, and Time‐Dependent NMR Spectroscopic Studies of (SP‐4‐3)‐Oxalato[(1R,2R,4R/1S,2S,4S)‐(4‐trifluoromethyl‐cyclohexane‐1,2‐diamine)]platinum(II)

The oxaliplatin derivative (SP‐4‐3)‐oxalato[(1R,2R,4R/1S,2S,4S)‐(4‐trifluoromethyl‐cyclohexane‐1,2‐diamine)]platinum(II) hosting a trifluoromethyl group at position 4 of the cyclohexane ring is presented. The ligand was synthesized as an 1R,2R,4R/1S,2S,4S racemic mixture starting from 4‐trifluoromethyl‐cyclohexanol over five steps and coordinated to platinum to yield first the dichlorido and subsequently the oxalato complex. This novel compound and its analogue featuring a (13C2)oxalate ligand were characterized by multinuclear (1H, 13C, 15N, 19F, 195Pt) one‐ and two‐dimensional NMR spectroscopy. Ligand exchange and adduct formation reactions with DMSO, NaCl, CaCl2, l‐methionine, and 5′‐GMP were investigated via time‐dependent measurements by 19F and 13C NMR spectroscopy. The cytotoxicity of the title complex was investigated in three human cancer cell lines; the IC50 values were found in the low micromolar range, attesting moderate to high antiproliferative activity, depending on the cell line.

Kinetics and mechanistic study of the reduction of $$\hbox {Mn}^{\mathrm{III}}$$ Mn III by oxalate in Salophen scaffold: relevance to oxalate oxidase

The trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $${\hbox {OH}_{2})_{2}}^{+}$$ and bioxalate ( $$\hbox {HOX}^{-})$$ in aqueous medium equilibrate rapidly to trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})$$ (HOX) followed by the acid dissociation equilibrium to the (aqua) mono oxalato complex. The slow redox reactions of trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})$$ (HOX/OX) $$^{0/-}$$ with $$\hbox {H}_{2}\hbox {OX}$$ , $$\hbox {HOX}^{-}$$ , $$\hbox {OX}^{2-}$$ obey second order kinetics satisfying 2:1 stoichiometry $$([\hbox {Mn}^{{\mathrm{III}}}]_{\mathrm{T}}/[\hbox {OX}]_{\mathrm{T}} = 2/1)$$ . The products are $$\hbox {Mn}^{{\mathrm{II}}}$$ and $$\hbox {CO}_{2}$$ . Acrylamide monomer has no effect on the rate constant and the reaction does not induce its polymerization. The rate and activation parameters for the various rate limiting paths are reported. The intramolecular reduction of $$\hbox {Mn}^{{\mathrm{III}}}$$ by the coordinated $$\hbox {HOX}^{-}$$ and $$\hbox {OX}^{2-}$$ in trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})(\hbox {HOX/OX})^{0/-}$$ could not be detected. Contrary to our expectation, it is observed that $$\hbox {H}_{2}\hbox {OX}$$ is a better reducing agent than $$\hbox {HOX}^{-}$$ for trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})(\hbox {HOX})$$ , the slowest being the redox reaction of $$\hbox {OX}^{2-}$$ with trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})(\hbox {OX})^{-}$$ . The molecular modelling by DFT depicts the structural trans effect in the oxalato complexes, it being maximum for trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})(\hbox {OX})^{-}$$ . The observed sequence of the redox activity of the oxalato complexes reflects the potential role of non-covalent interaction i.e. H-bonding, governing the proton controlled electron transfer process (PCET). The $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen/Salen) complexes may turn out to be good substitute candidates for Oxalo Oxidase (OXO) enzyme in alleviating the oxalate overload in plants and animal biochemistry. The trans- $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)( $$\hbox {OH}_{2})_{2}^{+}$$ undergoes equilibrium pre-association in aqueous medium with bioxalate forming $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)(HOX) $$(\hbox {OH}_{2})$$ and $$\hbox {Mn}^{{\mathrm{III}}}$$ (Salophen)(OX) $$(\hbox {OH}_{2})^{-}$$ which are inert to intramolecular reduction but undergo reduction via second-order paths by $$\hbox {H}_{2}\hbox {OX}$$ , $$\hbox {HOX}^{-}$$ and $$\hbox {OX}^{2-}$$ with decreasing reactivity sequence implying proton controlled process.

DEARYLATION IN THE INTERACTIONS BETWEEN (Et3NH)HC2O4 OR (Et3NH)2C2O4 AND SnPh3Cl: INFRARED STUDY

Five new oxalato, hydrogenoxalato and hydrogenocarbonato adducts (three) and complexes (two) obtained on allowing (Et<sub>3</sub>NH)HC<sub>2</sub>O<sub>4</sub> or (Et<sub>3</sub>NH)<sub>2</sub>C<sub>2</sub>O<sub>4</sub> to react with SnPh<sub>3</sub>Cl have been studied by infrared spectroscopy, then discrete structures suggested on the basis of spectroscopic data. The anions behave as monochelating ligands, the environments around the metallic centres being octahedral. In two of the compounds, the benzene molecules obtained<em> in situ </em>are lattice. In all these structures when considering the cation involved in extra hydrogen bonds, a supramolecular architecture may be obtained.

Self-propagation combustion method for the synthesis of solar active Nano Ferrite for Cr(VI) reduction in aqua system

Abstract The study aimed at the development of a facile route to the synthesis of a solar active nano ferrite via the self-propagation combustion protocol. The solar activity of the synthesised ferrite sample (FSP) was determined using the reduction of Cr(VI) to Cr(III) as a case study, in the presence of oxalic acid, as the hole scavenger. The analysis of the time-concentration profile data of the photoreduction reaction with the pseudo first order kinetic equation showed that the rate and half-life (t1/2) of photoreduction of Cr(VI) to Cr(III) is dependent on the initial Cr(VI) concentration. The photoreduction efficiency (PE) (%) of the FSP is a function of the initial FSP dosage and the hole scavenger. The determination of the influence of hydrochemistry on the PE (%) showed that Cr(VI) solution pH and ionic strength had no visible negative impact. Aside the presence of carbonate in the Cr(VI) solution, other anionic interfering species (i.e. NO−3, Cl− and SO3 2−) had minimal or no visible influence on the PE (%) values. The presence of carbonate, at higher concentration (i.e. ˃10 mg/L) significantly impacted on the PE values and hyperchromic shift in the absorbance values of the treated water from the photo reduction process was observed. The tendency of the Cr(III) that is formed from the photoreduction reaction to form Cr(III)-oxalato complex was confirmed after a certain minimum time of the photoreduction process.

NEW ZINC OXALATO AND HYDROGENOXALATO COMPLEXES: SYNTHESIS AND INFRARED STUDY

Five new oxalato and hydrogenoxalato complexes with ZnBr2 have been synthesized and studied by infrared. Discrete structures have been suggested in the basis of spectroscopic data. The environments around the zinc centre being trigonal bipyramidal, tetrahedral, octahedral or monocapped octahedral. The anions behave as monochelating ligands. When the cations and OH group are involved in extra hydrogen bonds, a supramolecular architecture may be obtained.

DEARYLATION IN THE INTERACTIONS BETWEEN (Et3NH)HC2O4 OR (Et3NH)2C2O4 AND SnPh3Cl: INFRARED STUDY

Five new oxalato, hydrogenoxalato and hydrogenocarbonato adducts (three) and complexes (two) obtained on allowing (Et3NH)HC2O4 or (Et3NH)2C2O4 to react with SnPh3Cl have been studied by infrared spectroscopy, then discrete structures suggested on the basis of spectroscopic data. The anions behave as monochelating ligands, the environments around the metallic centres being octahedral. In two of the compounds, the benzene molecules obtained in situ are lattice. In all these structures when considering the cation involved in extra hydrogen bonds, a supramolecular architecture may be obtained.

Hydrothermal synthesis, structures and magnetic properties of two new holmium(III) oxalato complexes

Two new holmium (Ho) oxalato complexes have been synthesized under hydrothermal conditions and structurally characterized. [Ho(OH)2]2(C2O4) (1) has a 3-D structure with Ho-(μ3-OH) hydroxide layers connected by μ4-bridging oxalate ligands forming a unique hybrid structure. Sr(H2O)4[Ho(C2O4)2(H2O)]2·2H2O (2) has a 3-D structure built through μ2-bridging oxalate ligands connecting hexagonal Ho oxalate layers with hydrated Sr2+ ions in the channels. Different oxalate ligand arrangements around the metal ions control the structural alterations among the lanthanoid double oxalates even with similar formulas. Both structures have been discussed and compared to the existing lanthanoid oxalato complexes. In addition, their vibration modes, thermal stabilities, electronic structures, and magnetic properties have been further investigated and reported. Both 1 and 2 show the deviation of the magnetic behaviors from the Curie–Weiss law due to the crystal field effects.

Understanding the nature of Metal Oxalato Complexes with Purine Nucleobase- A Quantum Chemical approach

For the past few decades many research efforts have been examined to understand the binding properties of nucleic acids and their constituents with metal ions, which aid to develop the new biologically active metallo drug

Solvato- and thermochromism study in oxalato-bridged dinuclear copper(II) complexes of bidentate diamine ligands

Two new oxalato complexes of the formula [Cu2(L)2(µ-ox)(MeOH)2](ClO4)2 (1) and [Cu2(L)2(µ-ox)](NO3)2 (2), where ox=oxalato and L=N,N′-dibenzylethane-1,2-diamine, were prepared and characterized by elemental analysis, IR and UV–vis spectroscopies and molar conductance measurements. The crystal structure of compound 1 was determined by single-crystal X-ray analysis. The compounds are solvatochromic and their solvatochromism was studied with different solvent parameter models using the stepwise multiple linear regression (SMLR) method with SPSS/PC software. It was demonstrated that the donor power of the solvent plays the most important role in the observed positive solvatochromism of the compounds. The complexes show irreversible thermochromism in solution due to the substitution of the weakly coordinated counter ions and coordinated solvents by solvent molecules.

Crystal structure and spectroscopic behavior of three new tris-oxalatoferrate(III) salts

A new general synthetic procedure for preparation of Na3[Fe(C2O4)3]·5H2O (1), Rb3[Fe(C2O4)3]·3H2O (2), and Cs3[Fe(C2O4)3]·2H2O (3) was developed. The crystal structures of these salts have been determined by single crystal X-ray diffraction. Salt 1 crystallizes in the monoclinic space group C2/c with Z = 8, salt 2 in P21/c with Z = 4, and salt 3 in P21/n with Z = 4. The three new salts and K3[Fe(C2O4)3]·3H2O, prepared for comparative purposes, were further characterized by infrared and 57Fe-Mössbauer spectroscopy. These spectra are discussed in comparison with those of related oxalato complexes.

Carbon kinetic isotope effects at natural abundances during iron-catalyzed photolytic cleavage of C[sbnd]C bonds in aqueous phase α,ω-dicarboxylic acids

Carbon kinetic isotope effects (KIEs) at natural abundances during photolysis of Fe3+-oxalato, malonato, and succinato complexes in aqueous solution were studied to identify the CC bond cleaving mechanism of Fe3+-oxalato complexes under sunlight irradiation. Observed overall KIEs were 5.9‰, 11.5‰, and 8.4‰, respectively. This variation is inconsistent with secondary carbon KIEs for the FeO bond cleavage, but consistent with primary carbon KIEs for sequential cleavage of FeO and CC bonds. Position-specific probability of 13C content estimated KIEs of 5.9‰, 17.2‰, and 17‰ for 12C13C bond cleavage, respectively, indicating the different KIEs for carboxyl-carboxyl and methyl-carboxyl cleavage.