Complexation of Indole-3-acetic Acid with Iron(III): Influence of Coordination on the π-Electronic System of the Ligand

 The iron(III) complex of indole-3-acetic acid (1) was prepared, and its physicochemical properties, mode of iron(III) coordination, and electronic structure were studied using UV/Vis, diffuse reflectance infrared Fourier transform (DRIFT), and transmission ⁵⁷Fe M?ssbauer spectroscopic techniques. The data obtained provide evidence that iron(III) is not only coordinated by the carboxylic O-donor atom, but also via the conjugated π-electronic system of the pyrrole moiety involving both the non-shared electronic pair of the heteroatom and the C(2)*C(3) double bond. Considering the well-known increased sensitivity of the pyrrole residue in indole derivatives to oxidation as compared to the benzene ring, as well as the formation of a triple complex (peroxidase-1-O₂) proposed for the enzymatic 1 oxidative degradation mechanism involving as a key step the Fe³⁺ → Fe²⁺ transition in the enzyme form as discussed in literature, it is concluded that iron(III) coordination with 1 can influence the redox properties of the pyrrole ring by affecting its π-electronic system.     

Amperometric Determination of Indole-3-acetic Acid Based on Platinum Nanowires and Carbon Nanotubes

Over the past few years, extensive research has been focused on the preparation, purification, and possible application of the CNT1-3. The unique electronic, chemical, and mechanical properties of CNT make it extremely attractive for electrochemical sensi…     

Study on the Fluorescence System of Oxolinic Acid‐Tb(III) and the Determination of Oxolinic Acid

Abstract

In Tris‐HCl buffer (pH=7.43), Tb³⁺ can react with oxolinic acid (OA) and form a 1:2 complex, which emits the intrinsic fluorescence of Tb³⁺. Based on this, a new fluorimetric method of determination of OA is developed. Under the optimum conditions, the enhanced fluorescence intensity of the system is proportional to the concentration of OA in the range of 1.5×10^?7～2.5×10^?5mol/L, and the detection limit is 5.5×10^?9 mol/L. Recovery test was also satisfactory. The experiments indicated that the luminescence mechanism was attributed to the M*–M luminescence.     

The Effect of Concentration Parameters on Complexation in the Iron(0)–Iron(II)–Glycine–Water System

The processes of formation of iron(II) complexes in aqueous glycine solutions in the pH range of 1.0–8.0 at 298 K and ionic strength of 1 mol/L (NaClO₄) are studied using Clark and Nikolskii’s oxidation potential method. The type and number of coordinated ligands, the nuclearity, and the total composition of the resulting complexes are determined. The following complex species are formed in the investigated system: [Fe(OH)(H₂O)₅]⁺, [FeHL(H₂O)₅]²⁺, [Fe(HL)(OH)(H₂O)₄]⁺, [Fe(OH)₂(H₂O)₄]⁰, [Fe₂(HL)₂(OH)₂(H₂O)₈]²⁺, and [Fe(HL)₂(H₂O)₄]²⁺. Their formation constants are calculated by the successive iterations method using Yusupov’s theoretical and experimental oxidation function. The model parameters of the resulting coordination compounds are determined.     

Influence of Excitation of the Lanthanide 4 fShell on Complexation with Organic Substrates in Solutions: 1. The Complexation of the β-Diketonate Tris(heptafluorodimethyloctanedionato)europium(III) with Sulfoxides in Benzene Solutions

Complexation of sulfoxides R¹R²S=O with the -diketonate Eu(fod)₃(fod is heptafluorodimethyloctanedionato) in the ground and excited states in benzene solutions was studied. Excitation of Eu(fod)₃was found to increase the formation constants and to reverse the sign of the enthalpy of complexation. The compensation effect was observed for the thermodynamic parameters: S ₀= (3.4 ± 0.4) × 10^–3H ₀+ (50.0 ± 4.7) in the ground state and S ^* ₀= (3.2 ± 0.4) × 10^–3H ^* ₀+ (62.0 ± 0.6) in the excited state of Eu(fod)₃. The enhancement of the stability of the complexes [Eu(fod)^* ₃· R¹R²S=O] is due to an increase in the entropy of complexation upon excitation of f–ftransitions in Eu(III).     

Influence of Excitation of the Lanthanide 4 fShell on Complexation with Organic Substrates in Solutions: 2. Isotope Effects in Complexation of Tris(heptafluorodimethyloctanedionato)europium(III) with Dimethyl Sulfoxide in Benzene Solutions

The effect of deuteration of dimethyl sulfoxide on the fluorescence quantum yield, temperature quenching of fluorescence, and its complexation with tris(heptafluorodimethyloctanedionato)europium(III) (Eu(fod)₃) in the ground and excited states was studied. It was found that excitation of f–ftransitions in Eu(III) increases the stability of Eu(fod)₃complexes with sulfoxides but has a very insignificantly influence on isotope effects. The deuterium effect is displayed to a small extent in altering the quantum yield and is accompanied by a decrease in the efficiency of temperature quenching of Eu(fod)^* ₃fluorescence.     

Synthesis,Crystal Structure and Spectral Property of a Water-bridged Co(Ⅱ) Coordination Polymer with 3-Flavonoxylacetic Acid Ligand

A new cobalt complex with flavonoid carboxylate ligand was synthesized and characterized. X-ray diffraction data revealed that the compound crystallizes in the monoclinic crystal system, space group P2_1/c with a = 7.936(3), b = 21.475(7), c = 20.010(7) ?, β = 102.856(14)o, V = 3325(2) ?~3, Z = 4, C_(34)H_(32)CoO_(15), M_r = 739.53, D_c = 1.477 g/cm~3, F(000) = 1532, μ = 0.591 mm~(-1), R = 0.1123 and w R = 0.1419. In the crystal structure, the Co(Ⅱ) shows 6 coordination geometry, and the flavonoid ligand coordinated with the Co(Ⅱ) ion in a monodentate mode. Hydrogen bonding interactions and π-π stacking interactions lead to the three-dimensional stacking of crystal and increase its stability. Moreover, the thermal stability and luminescent properties of the complex are also investigated. The fluorescence of the complex shows a great reduction of the intensity than that of the ligand.     

Complexation of Eu(III), Am(III) and Cm(III) with Dicarboxylates: Thermodynamics and Structural Aspects of the Binary and Ternary Complexes

The complexation of Eu(III), Am(III) and Cm(III) with dicarboxylate anions with O, N or S donor groups was measured in I=6.60 mol⋅kg⁻¹ (NaClO₄) at temperatures of 0–60 °C by potentiometry and solvent extraction. The complexation thermodynamics of these complexes show that their stability is due to highly favorable complexation entropies because the complexation enthalpies are endothermic. Luminescence studies with Eu(III) and Cm(III) were used to measure the hydration numbers of the complexes. NMR spectra of ¹H and ¹³C were used to determine the binding modes of La(III) with the ligands. The formation of 1:1:1 ternary complexes of M(EDTA)⁻ with the dicarboxylate ligands was studied to determine changes in coordination of the metal cation with formation of the ternary species. The complexation of ternary complexes changes from bidentate to monodentate as the chain length between the binding sites of the dicarboxylates increases from 1 (malonate) to 4 (adipate). DFT computations were used to confirm the structural aspects of the interaction of these complexes.     

Two Coordination Polymers with High Selectivity for Sensing Iron(Ⅲ) Constructed from Bifunctional Ligand

A new ligand [1-{2-(2-pyridyl)-benzo[d]imidazole}-2-(5-hydroxyisophthalic acid) ethane] was used to synthesize cadmium and cobalt based florescent organic frameworks successfully under solvothermal conditions. Single-crystal X-ray crystallography of both complexes as well as their thermal stability and luminescence properties was investigated. Much emphasis was placed on the newly synthesized Cd-complex which shows great sensitivity for the detection of Fe~(3+) ions and could be used as a potential probe to detect the Fe~(3+) ions.     

Complexation of Dioxovanadium (V) with CDTA in the Water + Methanol Solvent System

The solvent effect has been studied in this research for the interaction of the $ {\text{VO}}_{2}^{ + } $ VO 2 + cation with trans-1,2-diaminocyclohexane-N, N, N′, N′- tetraacetic acid monohydrate at T = 298 K, I = 0.10 mol·dm^?3 sodium perchlorate, and in the range of 0–45 % water + methanol mixtures. UV absorbance data as a function of pH and dissociation constants, obtained from potentiometric titrations, were used for the determination of stability constants. The Kamlet–Abboud–Taft (KAT) model has been investigated for a plausible interpretation and calculation of the linear solvation energy relationship coefficient contribution to the formation of three species VO₂H₂L, VO₂HL^? and VO₂L^2?, which were identified in this work.     

Temperature-controlled Structural Diversity of Two Cd(Ⅱ)Coordination Polymers Based on the Dicarboxylate Ligand

Two new 3-D Cd(Ⅱ) coordination polymers with p-phthalic acid (p-BDC) and 4,4'-dipyridyl-amine (4,4'-dpa),namely[Cd2(p-BDC)2(4,4'-dpa)2]n 1 and {[Cd(p-BDC)(4,4'-...     

Influence of Different Organic Carboxylate Anions on the Crystal Structure of Silver(Ⅰ)Coordination Polymers

The reaction of AgNO3 , 4,4′-bipyridine (bpy) and 2,2′-bipyridine-3,3′-dicarboxylic acid (H2bpdc)/2,2′-biquinoline-4,4′-dicarboxylic acid (H2bqdc)/1,3-benzenedicarboxylic acid (H2bdc) gave rise to block-like crystals of [Ag4(bpy)2(bpdc)2]·13H2O(1), [Ag2(bpy)(bqdc)(H2O)]·4.5H2O(2) and [Ag2(bpy)2(H2O)2](bdc)·3H2O(3) by slow evaporation. All the three complexes contain sandwich-like crystal structures, in which anionic sheets built up from different anions (bpdc2- , bqdc2- and bdc2- ) and lattice water molecules via rich hydrogen-bonding interactions are inserted between the cationic silver complex layers, and the abundant Ag···Ag, Ag···N and π-π stacking interactions further strengthen the 3D frameworks. The lattice water molecules are situated among the framework of crystal structure and stabilized by rich hydrogen-bonding interactions, and lattice water molecules may play a role in the orientation of organic anions in the crystal packing. Additionally, the thermal properties of 1, 2 and 3 were also discussed in detail.     

Complexation of Sc(III), Ga(III), In(III) and Ln(III) with Eriochrome Red B

Cyclic linear-sweep voltammetry was used to study the complexation of Sc(III), Ga(III), In(III) and Ln(III) with eriochrome red B (ERB). It was established that all metal ions investigated form complex compounds with azodye having a mole ratio, M(III):ERB = 1:2. The hydroxo forms of M(III) ions, which take part in interaction with ERB, were determined by the Nazarenko method. The stability constants for the formation of these chelates are nearly the same. It was shown that the reduction of the ligand in the complex does not only depend on the peculiarities of complexation, but the processes occurring in pre-electrode layer also influence it.     

Kinetic Determination of Iodide Traces Based on the Manganese(III) Metaphosphate–Arsenic(III) Reaction in the Presence of Orthophosphoric Acid

The kinetics of the iodide-catalyzed Mn(III) metaphosphate–As(III) reaction was studied in the presence of orthophosphoric acid. The reaction rate was followed spectrophotometrically at 516nm. It was established that orthophosphoric acid increased the reaction rate and that the extent of the non-catalytic reaction was extremely small. A kinetic equation was postulated and the apparent rate constant calculated. The dependence of the reaction rate on temperature was investigated and the energy of activation and other kinetic parameters determined. Iodide was determined under the optimal experimental conditions in the range 0.6–2.5ng·mL^–1 with a relative standard deviation of up to 6.7% and a detection limit of 0.12ngmL^–1. The effect of foreign ions on the accuracy of the determinations was also investigated.     

A 3D Homochiral Mn(Ⅱ) Coordination Polymer Based on the Ligand 2,2?-(Ethane-1,2-diylbis(oxy)) Dicinnamic Acid

A 3D homochiral coordination polymer [Mn(edca)]n(1) was synthesized from a flexible coupled cinnamic acid ligand, 2,2?-(ethane-1,2-diylbis(oxy)) dicinnamic acid(H_2 edca) and MnCl_2×4 H_2 O under solvothermal conditions. The complex crystallizes in orthorhombic, space group P2_12_12_1 with a = 5.5785(8), b = 13.0393(18), c = 23.133(3) ?, V = 1682.7(4) ?~3, M_r = 407.27, D_c = 1.608 Mg/cm~3, F(000) = 836, Z = 4, the final R = 0.0240 and wR = 0.0590 for 2983 observed reflections(I 2σ(I)). In 1, the edca2+ anions alternately bridge the Mn(Ⅱ) cations to form one-dimensional(1 D) infinite helical chains of [Mn(edca)]n, which are further connected by the ligands generating a three-dimensional(3D) homochiral network. The photoluminescence of 1 was also investigated in solid state at ambient temperature.     

Study on the Extraction of L-Phenylalanine with Organo-phosphoric Acid in Two and Three-phase System

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Spontaneous Reductive Elimination at Iridium(III) Induced by the Strong π-Acceptor Ligand Trifluorophosphane

The reaction of the cyclometalated five-coordinate 16 VE iridium(III) compound [IrCl(H)(P(tBu)₂C₆H₄-κ²P,C)(P(tBu)₂Ph)] ( 1 ) with the strong π-acceptor ligand trifluorophosphane resulted quickly in the quantitative formation of the new iridium(I) complex trans-[IrCl(PF₃)(P(tBu)₂Ph)₂] ( 2 ). This unexpected spontaneous reductive elimination was already observed in reactions of 1 with the very strong π-acceptor ligands CO and NO⁺. First indications during reactions of 1 with lesser strong π-acceptor ligands like alkyl or arylphosphanes did not show this inversion behavior of the cyclometalation. The title species 2 was characterized by spectroscopic methods and its molecular structure in the crystal was confirmed by X-ray crystallography.     

Activation of Iron (III) and Bismuth (III) Nitrates by Tungstophosphoric Acid: Solvent‐Free Oxidative Deprotection of Oximes to Carbonyl Compounds

Abstract

Tungstophosphoric acid (H₃PW₁₂O₄₀ · 6H₂O) has been used as a catalyst for a simple, rapid, selective, and solvent‐free cleavage of oximes to carbonyl compounds using iron (III) and bismuth (III) nitrates as oxidants.     

Synthesis,Structure and Luminescent Properties of Cd(Ⅱ) Coordination Polymers Based on 4-Nitrobenzoic Acid and Bis(imidazol) Ligand

A new Cd(Ⅱ) coordination polymer, [Cd_(0.5)(nba)(bib)_(0.5)]_(2n)(1, Hnba = 4-nitrobenzoic acid, bib = 1,4-bis(imidazol-1-yl)-butane), was synthesized at room temperature condition and characterized by IR spectra, elemental analyses, single-crystal and powder X-ray diffractions. Complex 1 belongs to the monoclinic system, C2/c space group, with a = 26.0600(14), b = 6.7889(4), c = 16.5825(9) ?, β = 118.8120(10)°, V = 2570.6(2) ?3, Z = 4. It shows one-dimensional chains and is further linked by π-π stacking interactions to yield a three-dimensional supramolecular structure. Thermal stability and luminescence of 1 were investigated.     

Syntheses and Structures of a New Tetrazylphosphonate Ligand and the Coordination Polymer Based on Zn~(Ⅱ)

A novel tetrazylphosphonate ligand, namely ethyl 4-(2-ethyl-2H-1,2,3,4-tetrazol-5-yl) benzylphosphonate(Et-L), was designed and successfully achieved from p-cyano benzyl chloride, based on which a zinc coordination polymer(1) with a 2D layer structure has been hydrothermally synthesized and structurally characterized by elemental analysis, IR, TGA and X-ray single-crystal diffraction. The colorless block crystals of H_2L·H_2O were also obtained under the same hydrothermal conditions, which belongs to monoclinic system, space group P2_1/c with a = 13.3141(7), b = 5.1650(3), c = 21.9839(18) ?, β = 115.307(5)°, V = 1366.69(15) ?~3, Z = 4, D_c = 1.391 mg/cm~(-3), Mr = 349.58, F(000) = 600, R = 0.0748 and wR = 0.1917 for 2392 observed reflections(I 2σ(I)). The colorless block crystals of complex 1([Zn(L)(H_2O)]_n) also belong to monoclinic system, space group P2_1/c with a = 22.7464(10), b = 6.0430(3), c = 9.7704(4) ?, β = 92.525(4)°, V = 1341.70(10) ?~3, Z = 4, D_c = 1.731 mg/cm_(-3), M_r = 349.58, F(000) = 712, R = 0.0596 and wR = 0.1688 for 2357 observed reflections(I 2σ(I)). Only the oxygen atoms of phosphonic group are coordinated with the metal zinc probably because the hydrogen atom of tetrazole has been substituted by ethyl group. Photoluminescence properties of the complex are also investigated.