Thermodynamics of Copper(II) Complexes of Diamino Diamides in Aqueous Solution

The equilibria occurring in aqueous solutions of N,N′-bis(β-carbamoylethyl)ethylenediamine, N,N′-bis(β-carbamoylethyl)trimethylenediamine, N,N′-bis(β-carbamoylethyl)-1,2-propylenediamine, and N,N′-bis(β-carbamoylethyl)-2-hydroxytrimethylenediamine with protons and copper(II) ions as well as the deprotonation reactions of the copper (II) complexes of these four ligands have been studied by calorimetry at T=25.0°C and I=0.10 mol dm^?3 (NaClO₄). The enthalpy changes and the entropy changes for these reactions are reported and discussed.     

Copper(II) complexes of diaminodiamides in aqueous solution

The basicity constants of N,N′-bis(β-carbamoylethyl)ethylenediamine, N,N′-bis(β-carbamoylethyl)trimethylenediamine, N,N′-bis(β-carbamoylethyl)-1,2-propylenediamine, and N,N′-bis-(β-carbamoylethyl)-2-hydroxyltrimethylenediamine were determined potentiometrically in 0.10 mol dm^?3 NaNO₃ at 25.0°C. The formation of Cu(II) complexes of these ligands and the CuO to CuN bond rearrangements at the two amide sites of these complexes were investigated quantitatively by potentiometric and spectrophotometric techniques under the same conditions. Electronic spectra of the Cu(II) complexes of these ligands and their deprotonated species formed in aqueous solution were measured and discussed.     

Reaction ofN,N-bis(chloromethyl)amides withN,N′-diacylated alkene(arylene)diamines

Reactions ofN,N-bis(chloromethyl)amides withN,N′-diacyl derivatives of ethylenediamine (oro-phenylenediamine) result in formation of the corresponding 1,3,5-triacylated perhydro-1,3,5-triazepines (or their benzoanalogs) or 1,3-diacylated imidazolidines (or their benzoanalogs). Reactions ofN,N-bis(chloromethyl)amides withN,N′-ditosylated trimethylenediamine occur in a similar way. The direction of the reactions depends on the type of the acyl substituents and the strength of the bases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2270–2273, November, 1998.     

Synthesis of 2-(2-hydroxyaroylmethylene)hexahydropyrimidines from 2-trichloromethylchromones and trimethylenediamine

The reactions of 2-trichloromethylchromones with trimethylenediamine in ethanol at room temperature afford 2-(2-hydroxyaroylmethylene)hexahydropyrimidines. Under analogous conditions, 2-methylchromone gives a mixture ofN,N′-trimethylenebis[3-amino-1-(2′-hydroxyphenyl)-2-buten-1-one] andN,N′-trimethylenebis(imine) of 2-hydroxyacetophenone. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2140–2143, November, 1999.     

N,N′-Bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid. A new chelating ligand for iron(III)

A new potentially chelating ligandN,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-dipropionic acid, (HBEP) has been prepared in high yield and its ionization constants have been determined by potentiometric and spectrophotometric methods. The stability constant for the Fe^III-HBEP chelate has been determined spectrophotometrically, and the ligational behaviour of HBEP with iron(III) compared with that of its homologue, HBED (N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid). IPCL Communication No. 169.     

Syntheses, structural determination and binding studies of nine-coordinate mononuclear (EnH2)1.5 [ErIII(Ttha)] · 3H2O and (EnH2)[ErIII(Egta)(H2O)]2 · 6H2O

In this work, the title complexes, (EnH₂)_1.5[Er^III(Ttha)] · 3H₂O (I) and (EnH₂)[Er^III(Egta)(H₂O)]₂ · 6H₂O (II), where En = ethylenediamine, H₆Ttha = triethylenetetramine-N,N,N′,N″,N″’,N″′-hexaacetic acid, H₄Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N′-tetraacetic acid, have been successfully synthesized. Their structures have been characterized by IR spectroscopy and single-crystal X-ray diffraction techniques. The X-ray diffraction reveals that I is nine-coordinated and crystallizes in the monoclinic crystal space group P2/n with cell dimensions a = 17.6058(16), b = 9.6249(9), c = 20.560(2) ?, β = 109.7440(10)°, and V = 3279.1(5) ?³. Compound II is also nine-coordinated and crystallizes in the monoclinic crystal space group P2₁/n with the cell dimensions a = 12.938(6), b = 12.651(5), c = 14.943(6) ?, β = 105.441(5)°, and V = 2357.5(17) ?³. In I, each EnH₂²⁺ cation connects three adjacent [Er^III(Egta)(H₂O)]⁻ complex anions through hydrogen bonds, while in I, there are two types of EnH₂ ²⁺ anions. One is highly symmetrical, forming hydrogen bonds with two neighboring [Er^III(Ttha)]³⁻ complex anions. The other anion connects three adjacent [Er^III(Ttha)]³⁻ complex anions through hydrogen bonds. These hydrogen bonds lead to the formation of 2D ladder-like layer structure.     

Amination of 4,6- and 2,4-dichloropyrimidines with polyamines

Amination of a double excess of 4,6-dichloropyrimidine with various diamines in the presence of cesium carbonate in boiling dioxane quantitatively afforded the corresponding N,N′-bis(6-chloropyrimidin-4-yl) derivatives, while its reactions with tri- and tetraamines gave N,N′,N″-tris- and N,N′,N″,N‴-tetrakis(6-chloropyrimidin-4-yl) derivatives. Equimolar amounts of 2,4-dichloro- or 4,6-dichloropyrimidine and diamines reacted in the presence of Pd(0) complexes to form macrocyclic compounds containing pyrimidine fragments. Catalytic reactions of 4 equiv of diamines with 4,6-dichloropyrimidine can lead to the formation of 4,6-bis-(diamino)pyrimidines. Relations between the yield and the nature of diamine and catalytic system were found.     

Spectroscopic and thermal investigations of complexes of Cr<Superscript>III</Superscript>, Mn<Superscript>II</Superscript>, Zn<Superscript>II</Superscript> &; Cd<Superscript>II</Superscript> - carboxamide

Complexes of Cr^III, Mn^II, Zn^II & Cd^II with the polydentate carboxamide ligandN′, N′′-bis(3-carboxy-1-oxoprop-2-enyl) 2-Amino-N-arylbenzamidine (H₂L) have been synthesized and characterized by elemental analyses, spectroscopic studies (Vibrational, electronic, ESR and ¹H-NMR), magnetic susceptibility measurements, thermal studies and powder diffraction studies. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicates octahedral or tetrahedral geometry around the metal ions, has been supported by magnetic susceptibility measurements. The results of electron spin resonance & ¹H-NMR spectra have supported the results of other spectral techniques. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. Powder diffraction determines the cell parameters of the complexes.     

Models for the active site in galactose oxidase: Structure, spectra and redox of copper(II) complexes of certain phenolate ligands

Galactose oxidase (GOase) is a fungal enzyme which is unusual among metalloenzymes in appearing to catalyse the two electron oxidation of primary alcohols to aldehydes and H₂O₂. The crystal structure of the enzyme reveals that the coordination geometry of mononuclear copper(II) ion is square pyramidal, with two histidine imidazoles, a tyrosinate, and either H₂O (pH 7.0) or acetate (from buffer,pH 4-5) in the equatorial sites and a tyrosinate ligand weakly bound in the axial position. This paper summarizes the results of our studies on the structure, spectral and redox properties of certain novel models for the active site of the inactive form of GOase. The monophenolato Cu(II) complexes of the type [Cu(L1)X][H(L1) = 2-(bis(pyrid-2-ylmethyl)aminomethyl)-4-nitrophenol and X⁻ = Cl⁻ 1, NCS⁻ 2, CH₃COO⁻ 3, ClO₄ ⁻ 4] reveal a distorted square pyramidal geometry around Cu(II) with an unusual axial coordination of phenolate moiety. The coordination geometry of 3 is reminiscent of the active site of GOase with an axial phenolate and equatorial CH₃COO⁻ ligands. All the present complexes exhibit several electronic and EPR spectral features which are also similar to the enzyme. Further, to establish the structural and spectroscopic consequences of the coordination of two tyrosinates in GOase enzyme, we studied the monomeric copper(II) complexes containing two phenolates and imidazole/pyridine donors as closer structural models for GOase. N,N-dimethylethylenediamine and N,N’-dimethylethylenediamine have been used as starting materials to obtain a variety of 2,4-disubstituted phenolate ligands. The X-ray crystal structures of the complexes [Cu(L5)(py)], (8) [H₂(L5) = N,N-dimethyl-N’,N’-bis(2-hydroxy-4-nitrobenzyl) ethylenediamine, py = pyridine] and [Cu(L8)(H₂O)] (11), [H₂(L8) = N,N’-dimethyl-N,N’-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine] reveal distorted square pyramidal geometries around Cu(II) with the axial tertiary amine nitrogen and water coordination respectively. Interestingly, for the latter complex there are two different molecules present in the same unit cell containing the methyl groups of the ethylenediamine fragmentcis to each other in one molecule andtrans to each other in the other. The ligand field and EPR spectra of the model complexes reveal square-based geometries even in solution. The electrochemical and chemical means of generating novel radical species of the model complexes, analogous to the active form of the enzyme is presently under investigation.     

Multinuclear NMR investigation on organometallic gold(III) pentafluorophenylarylazoimidazole complexes

Reaction of [Au(C₆F₅)(tht)₂Cl](OTf) with RaaiR′ in CH₂Cl₂ medium leads to [Au(C₆F₅)(RaaiR′)Cl](OTf) [RaaiR′ = p-R–C₆H₄–N=N–C₃H₂–NN-1-R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), tht is tetrahydrothiophen]. The maximum molecular peak of [Au(C₆F₅)(MeaaiMe)Cl] is observed at m/z 599.51 (100 %) in the FAB mass spectrum. Ir spectra of the complexes show –C=N– and –N=N– stretching near at 1590 and 1370 cm⁻¹ and near at 1510, 955, 800 cm⁻¹ due to the presence of pentafluorophenyl ring. The ¹H-NMR spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph shows AB type quartets. ¹³C-NMR spectrum of complexes confirm the molecular skeleton. In the ¹H-¹H-COSY spectrum as well as contour peaks in the ¹H-¹³C HMQC spectrum for the present complexes, assign the solution structure and stereoretentive conformation. The electrochemistry gives the ligand reduction peaks.     

Gold(I)-diphenylphosphinomethane–arylazoimidazole: synthesis and multinuclear NMR investigation

Reaction of [Au₂(dppm)Cl₂] with AgOTf in CH₂Cl₂ medium followed ligand addition and leads to [Au₂(dppm)(RaaiR′)](OTf) [RaaiR′ = p-R–C₆H₄–N = N–C₃H₂–NN–1–R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion, and dppm is the diphenylphosphinomethane-ring]. The ¹H-n.m.r. spectral measurements suggest methylene, –CH₂–, in RaaiEt gives a complex AB type multiplet while in RaaiCH₂Ph it shows AB type quartets with coupling constant of avg. 6 Hz. Considering all the moities there are a lot of different carbon atoms in the molecule which gives a lot of different peaks in the ¹³C-n.m.r spectrum. In the ¹H–¹H-COSY spectrum of the present complexes and contour peaks in the ¹H–¹³C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive transformation in each step.     

Synthesis,characterization and catalytic properties of heterogeneous iron(III) tetradentate Schiff base complexes for the aerobic epoxidation of styrene

A series of hybrid mesoporous SBA-15 materials containing four iron(III) Schiff base complexes of the type [FeL ^x (NO₃)] (x = 4–7, L = N,N′-bis(salicylidene)ethylenediamine, N,N′-bis(salicylidene)diethylenetriamine, N,N′-bis(salicylidene)o-phenylenediamine, N,N′-bis(3-nitro-salicylidene)ethylenediamine) was synthesized by a post-grafting route. The XRD, N₂ adsorption/desorption and TEM measurements confirmed the structural integrity of the mesoporous hosts, and the spectroscopic characterization techniques (FT-IR, UV–vis spectroscopy, ¹H NMR) confirmed the ligands and the successful anchoring of iron(III) Schiff base complexes over the modified mesoporous support. Quantification of the supported ligand and metal was carried out by TG/DSC and ICP-AES techniques. The catalyst FeL⁷-SBA resulting from N,N′-bis(3-nitro-salicylidene)ethylenediamine) ligand was considerably active for the aerobic epoxidation of styrene, in which the highest conversion of styrene reached 83.6%, and the selectivity to styrene oxide was 83.0%. Moreover, it was also found that the catalytic activity increases with the decrease in the electron-donating ability of the Schiff bases, and the selectivity varies according to the types of substituents in the ligands.     

New twisted-saddle dodecanuclear iron(III) clusters with adamantane-like [Fe4O6] core

Reactions of a hexadentate ligand N,N,N’,N’-tetrakis(2-hydroxyethyl)ethylenediamine (H₄edte) with different iron(III) salts in different solvents yielded three new twisted-saddle Fe12 clusters with adamantane-like [Fe₄O₆] inner core. Preliminary magnetic studies show that strong intracluster anti-ferromagnetic interaction exists in both 1 and 3, generating the S _T = 0 spin ground state.     

Crystal structures of the complexes of rare earth picrates with N, N, N′, N′-tetraphenyl-3, 6-dioxaoctanediamide

The complexes of rare earth picrate with N, N, N′, N′-tetraphenyl-3, 6-dioxaoctanediamide (TDD), [Eu(pic)₃(TDD)]-2CH₃CN and [Y(pic)₃(TDD)], have been synthesized. The crystal structures reveal that TDD acts as a tetradentate ligand, forming a ring-like coordination structure with its oxygen atoms together with one oxygen atom of the bidentate picrate. In the Eu (III) complex, the europium ion with a larger ionic radius lies out of the ring, while in the Y (III) complex, the yttrium ion with a smaller ionic radius enters the cavity of the ligand. The structures of the complexes are greatly affected by the ionic radii due to participation of the picrates in coordination. Project supported by the National Natural Science Foundation of China, the Doctoral Foundation of the State Education Commission of China, and the Climb Plan Foundation of the State Science and Technology Commission of China.     

Kinetics and Mechanism of the Reactions of Picolinic Acid with Dichloro-{1-alkyl-2-(arylazo)imidazole}palladium(II) Complexes

The reaction between Pd(N,N′)Cl₂ [N,N′ ≡ 1-alkyl-2-(arylazo)imidazole (N,N′) and picolinic acid (picH) have been studied spectrophotometrically at λ = 463 nm in MeCN at 298 K. The product is [Pd(pic)₂] which has been verified by the synthesis of the pure compound from Na₂[PdCl₄] and picH. The kinetics of the nucleophilic substitution reaction have been studied under pseudo-first-order conditions. The reaction proceeds in a two-step-consecutive manner (A → B → C); each step follows first order kinetics with respect to each complex and picH where the rate equations are: Rate 1 = {k′₀ + k′₂[picH]₀} × [Pd(N,N′)Cl₂] and Rate 2 = {k′′₀ + k′′₂[picH]₀}[Pd(N,O)(monodentate N,N′)Cl₂] such that the first step second order rate constant (k′₂) is greater than the second step second order rate constant (k′′₂). External addition of Cl⁻ (as LiCl) suppresses the rate. Increase in π-acidity of the N,N′ ligand, increases the rate. The reaction has been studied at different temperatures and the activation parameters (Δ^‡H° and Δ^‡S°) were calculated from the Eyring plot.     

Synthesis,Spectra and Electrochemistry of Dinitro-bis-{1-alkyl-2-(arylazo) imidazole} Ruthenium(II). Nitro-nitroso Derivatives and Reactivity of the Electrophilic {Ru-NO}<Superscript>6</Superscript>System

Ag⁺ assisted aquation of blue cis-trans-cis-RuCl₂(RaaiR′)₂ (4–6) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH₂)₂(RaaiR′)₂](ClO₄)₂ [Raai R′=p-R-C₆H₄ N=N–C₃H₂–NN–1–R′, (1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), OMe (b), NO₂ (c) and R′ = Me (1/4/7/10), CH₂CH₃ (2/5/8/11), CH₂Ph (3/6/9/12)] that have been reacted with NO₂⁻in warm EtOH resulting in violet dinitro complexes of the type, Ru(NO₂)₂(RaaiR′)₂ (7–9). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the compounds, (7b–9b) with conc. HClO₄ nitro-nitrosyl derivatives, [Ru(NO₂)(NO)(OMeaaiR′)₂](ClO₄)₂ (10b–12b) are isolated. The solution structure and stereoretentive transformation in each step have been established from ¹H n.m.r. results. All the complexes exhibit strong MLCT transitions in the visible region. They are redox active and display one metal-centred oxidation and successive ligand-based reductions. The redox potentials of Ru(III)/Ru(II) (E_1/2^M) of (10b–12b) are anodically shifted by ∼ ∼0.2 V as compared to those of dinitro precursors, (7b–9b). The ν(NO) >1900 cm⁻¹ strongly suggests the presence of linear Ru–NO bonding. The electrophilic behaviour of metal bound nitrosyl has been proved in one case (12b) by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group, and the heteroleptic tris chelates thus formed have been characterised.     

Complexation of (carbamoylmethyl)diphenylphosphine sulfide with silver nitrate. The structure of the polymeric complex [Ag2{Ph2P(S)CH2C(O)NH2}2(NO3)2] n

The reaction of (carbamoylmethyl)diphenylphosphine sulfide with AgNO₃ yields the polymeric complex [Ag₂{Ph₂P(S)CH₂C(O)NH₂}₂(NO₃)₂] _n . Its structure was established by X-ray diffraction analysis. The coordination environments about both Ag⁺ cations are formed by five donor atoms, two of which are bonded to the metal atom substantially more weakly than the remaining three atoms. The compositions of the coordination polyhedra are different: ({AgSO′(C)O(N)O₂(N′)} and {AgS′ SO(C)O₂(N)}). The coordinated ligands differ in their functions: one ligand chelates the metal cation and its sulfur atom is additionally bonded to the second cation, while the second ligand acts as a bridge between the two different cations. The structure of the complex and the character of the interaction between the ligand and AgNO₃ are substantially affected by the network of hydrogen bonds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 838–845, April, 1997.     

A novel series of nickel(II)-dppe-arylazoimidazole complexes. Synthesis and spectroscopic characterization

Reaction of [Ni(dppe)Cl₂/Br₂] with AgOTf in CH₂Cl₂ medium following ligand addition leads to [Ni(dppe)(OSO₂CF₃)₂] and then [Ni(dppe)(RaaiR)](OSO₂CF₃)₂ [RaaiR′ = p–R–C₆H₄–N=N–C₃H₂–NN-1–R′,(1–3), abbreviated as N,N′-chelator, where N(imidazole) and N(azo) represent N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion]. ³¹P{¹H}-NMR confirm that stable bis-chelated square planar Ni(II) azoimine–dppe complex formation with one sharp peaks. The ¹H NMR spectral measurements suggest azoimine link is present with lot of phenyl protons in the aromatic region. Considering all the moities there are a lot of different carbon atoms in the molecule which gives many different peaks in the ¹³C(¹H)-NMR spectrum. In the ¹H-¹H COSY spectrum in the present complexes and contour peaks in the ¹H-¹³C-HMQC spectrum in the present complexes, assign the solution structure and stereoretentive conformation in each complexes.     

Syntheses, structural determination, and binding studies of nine-coordinate mononuclear complexes (EnH2)3[EuIII(Etha)]2 · 11H2O and (EnH2)[EuIII(Egta)(H2O)]2 · 6H2O

Two novel ethylenediaminium salt of europium complexes with aminopolycarboxylic acid ligands, (EnH₂)₃[Eu^III(Ttha)]₂ · 11H₂O (I) (En is ethylenediamine, H₆Ttha is triethylenetetramine-N,N,N′,N″,N‴,N‴-hexaacetic acid) and (EnH₂)[Eu^III(Egta)(H₂O)]₂ · 6H₂O (II) (H₄Egta is ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) complexes were synthesized, and their crystal structures were determined by single-crystal X-ray diffraction techniques. Both of the two complexes adopt nine-coordinate structures with the pseudo-monocapped square antiprism and crystallize in the monoclinic crystal system with the P2₁/n space group. The crystal data for complex I are as follows: a = 17.8262(8), b = 19.3137(5), c = 20.6233(8) ?, β = 111.301(2)°, V = 6615.3(4) ?³, Z = 8, ρ _c = 1.677 mg/m³, μ = 1.981 mm⁻¹, F(000) = 3432, R = 0.0308, and wR = 0.0737 for 43622 observed reflections with I ≥ 2σ(I). The crystal data for complex II are as follows: a = 12.952(3), b = 12.618(2), c = 14.809(3) ?, β = 105.695(2)°, V = 2330.0(8) ?³, Z = 4, ρ _c = 1.800 mg/m³, μ = 2.765 mm⁻¹, F(000) = 1276, R = 0.0297, and wR = 0.0638 for 18416 observed reflections with I ≥ 2σ(I). One remarkable feature of the two complexes is that the protonated [EnH₂²⁺] cations conjugating to [Eu^III(Ttha)]₂⁶⁻ and [Eu^III(Egta)(H₂O)]₂²⁻ complex anions are reviewed, respectively, which open the path for the Eu^III complexes conjugating with other various biomolecules.     

Thermochemical study of three dimethylpyrazine derivatives

The standard (p ⁰=0.1 MPa) molar enthalpies of formation, in the gaseous phase, at T-298.15 K, for 2,5-dimethylpyrazine (2,5-DMePz) and for the two dimethylpyrazine-N,N′-dioxide derivatives, 2,3-dimethylpyrazine-1,4-dioxide (2,3-DMePzDO) and 2,5-dimethylpyrazine-1,4-dioxide (2,5-DMePzDO), were derived from the measurements of standard massic energies of combustion, using a static bomb calorimeter, and from the standard molar enthalpies of vaporization or sublimation, measured by Calvet microcalorimetry. The mean values for the molar dissociation enthalpy of the nitrogen-oxygen bonds, 〈DH _m⁰〉(N-O), were derived for both N,N′-dioxide compounds. These values are discussed in terms of the molecular structure of the two N,N′-dioxide derivatives and compared with 〈DH _m⁰〉(N-O) values previously obtained for other N-oxide derivatives.