Photolytic CO-substitution reaction of organoiron thiocarboxylate derivatives CpFe(CO)2SCOR (R=alkyl, aryl) with diphosphines (Ph2P(CH2)nPPh2) (n=1-6): X-ray crystal structure of [CpFe(dppm)SCO(3,5-(NO2)2C6H3)]

The photolytic CO-substitution reaction of the organoiron thiocarboxylate complexes CpFe(CO)₂SCOR (R=CH₃, 2-CH₃C₆H₄, 2-NO₂C₆H₄, 4-NO₂C₆H₄, 3,5-(NO₂)₂C₆H₃) with diphosphines (Ph₂P(CH₂)_nPPh₂) [n=1 (dppm), n=2 (dppe), n=3 (dpppr), n=4 (dppb), n=5 (dppp), n=6 (dpph)] at room temperature using 1:2 (metal-ligand) molar ratio afforded exclusively the disubstituted complexes CpFe(Ph₂P(CH₂)_nPPh₂)SCOR when n=1, 2 and 3 and the monosubstituted analogs CpFe(CO)(Ph₂P(CH₂)_nPPh₂)SCOR when n=4, 5 and 6. This reaction was found to be strongly influenced by the backbone length of the diphosphine ligand, the nature of the R group of the thiocarboxylate moiety and the metal-ligand molar ratios. The crystal structure of CpFe(dppm)SCO(3,5-(NO₂)₂C₆H₃) was determined.     

Extraction of peroxidase from bitter gourd (Momordica charantia) by three phase partitioning with dimethyl carbonate (DMC) as organic phase

Three phase partitioning (TPP) is most renowned technique used for extraction and purification of natural products. In previous studies of TPP, t-butanol is mainly used as an organic phase. This is the first report that explores ability of dimethyl carbonate (DMC) in the field of TPP as an alternate solvent for t-butanol. In the present study TPP process with t-butanol and DMC as organic phase along with different salts was applied to waste bitter gourd powder to obtained peroxidase enzyme. DMC was found to be compatible with most of salts such as ammonium sulphate and sodium citrate and explored as more efficient solvent than t-butanol. This TPP system provides 4.84 fold purity of peroxidase enzyme at optimum source concentration of 0.15 g/mL, with a system comprising DMC as organic phase, sodium citrate (20%) as salt, agitation speed 120 rpm, pH 7, temperature 30 °C and extraction time of 3 h. Present study has aimed for extraction and separation of peroxidase from bitter gourd waste with TPP technique and ensures the scope of carbonated solvents in extraction and purification of proteins.     

The coordination chemistry of cationic main group clusters: syntheses and structures of [Fe3(Se2)2(CO)10] and [Fe4(Se2)3(CO)12]

The reactions of the polysulfur and selenium cationic clusters S₈²⁺ and Se₈²⁺ with various iron carbonyls were investigated. Several new chalcogen containing iron carbonyl cluster cations were isolated, depending on the nature of the counteranion. In the presence of SbF₆⁻ as a counterion, the cluster [Fe₃(E₂)₂(CO)₁₀] [SbF₆]₂·SO₂ (E = S, Se) could be isolated from the reaction of E₈²⁺ and excess iron carbonyl. The cluster is a picnic-basket shaped molecule of two iron centers linked by two Se₂ groups, with the whole fragment capped by an Fe(CO)₄ group. Crystallographic data for C₁₀O₁₂Fe₃Se₄Sb₂F₁₂S (I): space group monoclinic P2₁/c, A = 11.810(9), b = 24.023(6), c = 10.853(7) Å, β = 107.15(5)°, V = 2942(3) ų, Z = 4, R = 0.0426, R_w = 0.0503. When Sb₂F₁₁⁻ is present as the counterion, or Se₄[Sb₂F₁₁]₂ is used as the cluster cation source, a different cluster can be isolated, which has the formula [Fe₄(Se₂)₃(CO)₁₂] [SbF₆]₂·3SO₂. The dication contains two Fe₂Se₂ fragments bridged by an Se₂ group. Crystallographic data for C₁₂O₁₈Fe₄Se₆Sb₂F₁₂S₃ (III): space group triclinic , b = 18.400(9), C = 10.253(4) Å, = 93.10(4), β = 103.74(3), γ = 93.98(3)°, V = 1995(1) ų, Z = 2, R = 0.0328, R_w = 0.0325. The CO stretches in the IR spectrum all show a large shift to higher wavenumbers, suggesting almost no τ backbonding from the metals. This also correlates with the observed bond distances. All the compounds are extremely sensitive to air and water, and readily lose SO₂ when removed from the solvent. Thus all the crystals were handled at −100°C. The clusters seem to be either insoluble or unstable in all solvents investigated.     

Reaction of [Pt{Fe(CO)3(NO)}2(PhCN)2] with diphenyl(2-pyridyl)phosphine selenide. Crystal structure of [(CO)3Fe(μ3-Se){Pt(CO)P(2-C5H4N)Ph2}2] and its theoretical study

The reaction between the linear trinuclear complex [Pt{Fe(CO)₃(NO)}₂(PhCN)₂] and Ph₂(2-C₅H₄N)PSe led to the isolation and characterization of the 46-electron cluster [(CO)₃Fe(μ₃-Se){Pt(CO)P(2-C₅H₄N)Ph₂}₂] (1), whose structure has been determined by X-ray diffraction methods. The cluster typology, which consists of an open triangle Pt---Fe---Pt capped by a μ₃-Se atom, is rather rare. The chemical bonding in 1 and in similar systems has been analyzed through density functional theory (DFT) and qualitative MO approaches. A strict analogy with the well understood L₂M(μ-acetylene)ML₂ systems is invoked by considering 1 as formed by the (CO)₃FeSe tetrahedral unit stabilized by sidewise interactions of the triple bond with two d¹⁰-L₂M fragments. Otherwise, the 18-electron (CO)₃FeSe monomer is unstable as an isolate molecule. This is confirmed by our DFT calculations that indicate how the well characterized dimer (CO)₃Fe(μ-Se₂)Fe(CO)₃ lies as much as, approximately, 58 kcal mol⁻¹ deeper in energy. Finally, by considering an analogy with [L₂M(μ-dichalcogen)ML₂]^{0, +2} redox systems (M=Pd, Pt), reduction of 1 to a dianion has been hypothesized and the structure of the latter has been tentatively explored by DFT calculations.     

Exploring the midgut proteome of partially fed female cattle tick (Rhipicephalus (Boophilus) microplus)

The continued development of effective anti-tick vaccines remains the most promising prospect for the control of the cattle tick, Rhipicephalus (Boophilus) microplus. A vaccine based on midgut proteins could interfere with successful tick feeding and additionally interfere with midgut developmental stages of Babesia parasites, providing opportunities for the control of both the tick and the pathogens it transmits. Midgut proteins from partially fed adult female cattle ticks were analysed using a combination of 2-DE and gel-free LC-MS/MS. Analysis of the urea-soluble protein fraction resulted in the confident identification of 105 gut proteins, while the PBS-soluble fraction yielded an additional 37 R. microplus proteins. The results show an abundance of proteins involved in mitochondrial ATP synthesis, electron transport chain, protein synthesis, chaperone, antioxidant and protein folding and transport activities in midgut tissues of adult female ticks. Among the novel products identified were clathrin-adaptor protein, which is involved in the assembly of clathrin-coated vesicles, and membrane-associated trafficking proteins such as syntaxin 6 and surfeit 4. The observations allow the formulation of hypotheses regarding midgut physiology and will serve as a basis for future vaccine development and tick-host interaction research.     

Syntheses and structures of Group 12 metal thioacetate anions, [M(SC{O}Me)nCl4−n] (n=3 and 4) and [Cd2Cl2(SC{O}Me)4]

We have utilized the possibility of altering the ratio of reactants to result in tetrahedral anions, [M(SC{O}Me)_nCl_4−n]²⁻ (n=3, 4) and [Cd₂Cl₂(SC{O}Me)₄]²⁻. Complexes of the formula [Ph₄P]₂[M(SC{O}Me)₄] (M=Zn(II) (1), Cd(II) (2) or Hg(II) (3)) were synthesized by the reaction of thioacetate ligand with the metal salts and Ph₄PCl in 4:1:2 molar ratio in suitable solvents. The geometry of Zn(II) in 1 is nearly tetrahedral and the distortion in tetrahedron increases in the order of 1<2<3 as observed from the SMS angles in the crystal structures. The tendency of monoanionic complexes [Ph₄P][M(SC{O}Me)₃] to react with 1 mole equivalent of Ph₄PCl resulted in complexes of the type [Ph₄P]₂[M(SC{O}Me)₃Cl] (M=Cd(II) (4) or Hg(II) (5)). In the structures of 4 and 5, three sulfur atoms and one chloride atom occupy the corners of the tetrahedron around the metal centers. However, in a 4:2:2 or 2:1:2 molar reaction of Me{O}CS⁻ with CdCl₂ and Ph₄PCl in aqueous medium resulted in a chloro bridged dimer, [Ph₄P]₂[Cd₂(μ-Cl)₂(SC{O}Me)₄] (6) as determined by X-ray crystallography.     

Electronic absorption and MCD spectra for octacyanometallate complexes M(CN)8, M=Mo(IV), W(IV), n=4 and Mo(V), W(V), n=3

Electronic absorption and 8.0 T magnetic circular dichroism (MCD) spectra are reported for M(CN)₈ ⁴⁻, M=Mo(IV) and W(IV), in aqueous solution and M(CN)₈ ³⁻, M=Mo(V) and W(V), in acetonitrile solutions. In addition some absorption and MCD spectra are reported for the M(CN)₈ ³⁻ ions embedded in thin poly methyl methacrylate (PMMA) plastic films at temperatures from 295 to 10 K. The temperature dependence of the MCD spectra confirms the presence of C terms. The solution and PMMA spectra for the both Mo and W complexes in either the IV or V oxidation states are remarkably similar to each other for the same oxidation state and are interpreted within a D_2d structural framework for the isotropic environment. The weak bands below 3.0 μm⁻¹ (1 μm⁻¹=10⁴ cm⁻¹) for the M(IV) complexes are assigned as metal-localized ligand field (LF) transitions. LF transitions are also suggested for weaker unresolved absorption between 3.0 and 3.6 μm⁻¹ for the M(V) ions. The intense bands above 3.6 μm⁻¹ for M(IV) and 4.6 μm⁻¹ for M(V) complexes are interpreted as metal to ligand charge transfer (MLCT) from the metal b₁(x²−y²) HOMO to CN⁻-based π * orbitals. The prominent intense bands observed below 4.5 μm⁻¹for the M(V) complexes are assigned as ligand to metal charge transfer (LMCT) from occupied non-bonding or weakly π bonding CN⁻ orbitals to the half-filled b₁(x²−y²) HOMO.     

Structures and excitation energies of ozone-water clusters O3(H2O)n (n = 1-4)

Hybrid density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been carried out for ozone-water clusters O₃(H₂O)_n (n = 1-4) in order to obtain hydration effects on the absorption spectrum of ozone. The first water molecule in n = 1 is bound to the ozone molecule by an oxygen orientation form in which the oxygen atom of H₂O orients the central oxygen atom of O₃. In n = 2, the water dimer is bound to O₃ and then the cyclic structure is formed as the most stable structure. For n = 3 (or n = 4), the cyclic water trimer (or tetramer) is bound by a hydrogen bond to the ozone molecule. The TD-DFT calculations of O₃(H₂O)_n (n = 0-4) show that the first and second excitation energies of O₃ are blue-shifted by the interaction with the water clusters. The magnitude of the spectral shift is largest in n = 2, and the shifts of the excitation energies are +0.07 eV for S₁ and +0.13 eV for S₂ states. In addition to the spectral shifts (S₁ and S₂ states), it is suggested that a charge-transfer band is appeared as a low-lying excited state above the S₁ and S₂ states. The origin of the spectrum shifts was discussed on the basis of theoretical results.     

Reactions of {4-[bis(2-chloroethyl)amino]phenyl}acetic acid (phenylacetic acid mustard) with 2'-deoxyribonucleosides

Phenylacetic acid mustard (PAM; 2), a major metabolite of the anticancer agent chlorambucil (CLB; 1), was allowed to react with 2'-deoxyadenosine (dA), 2'-deoxyguanosine (dG), 2'-deoxycytidine (dC), 2'-deoxy-5-methylcytidine (dMeC), and thymidine (T) at physiological pH (cacodylic acid, 50% base). The reactions were followed by HPLC and analyzed by HPLC/MS and/or (1)H-NMR techniques. Although the predominant reaction observed was hydrolysis of PAM, 2 also reacted with various heteroatoms of the nucleosides to give a series of products: compounds 5-31. PAM (2) was found to be hydrolytically slightly more stable than CLB (1). The principal reaction sites of 2 with dA, dG, and with all pyrimidine nucleosides were N(1), N(7), and N(3), resp. Also, several other adducts were detected and characterized. There was no significant difference in the reactivity of 1 and 2 with dG, dA or T, but the N(3) dC-PAM adduct was deaminated easier than the corresponding CLB derivative. The role of PAM-2'-deoxyribonucleoside adducts on the cytotoxic and mutagenic properties of CLB (1) is discussed.     

The mononuclear and dinuclear dimethoxyethane adducts of lanthanide trichlorides [LnCl3(DME)2]n, n=1 or 2, fundamental starting materials in lanthanide chemistry: preparation and structures

Some new dimethoxyethane (DME) adducts of lanthanide trichlorides of formula [LnCl₃(DME)₂]_n, n=1 or 2; (n=2, Ln=La, Ce, Pr, Nd; n=1, Ln=Eu, Tb, Ho, Tm, Lu) have been prepared by treating Ln₂O₃, or LnCl₃ · nH₂O, or Ln₂(CO₃)₃, in DME as medium, with thionyl chloride at room temperature, eventually in the presence of water in the case of Ln₂O₃ and Ln₂(CO₃)₃. The complexes from lanthanum to praseodymium included are chloro-bridged dimers. In the case of neodymium, the new results complement the literature data, showing that both the mononuclear and dinuclear species exist: neodymium can therefore be regarded as the turning element from dinuclear to mononuclear structures along the series. Only mononuclear complexes were isolated in the Eu-Lu sequence. The lanthanide contraction has been evaluated on the basis of the Ln-O and Ln-Cl bond distances on the isotypical series of the mononuclear complexes LnCl₃(DME)₂ covering a range of 12 atomic numbers.     

Homogeneous oxidative coupling catalysts: stoichiometry and characterization of the first stable oxotetranuclear solids [(Pip)nCuX]4O2 (n=1 or 2, Pip=piperidine, X=Cl, Br, I)

Copper(I) halides react quantitatively with piperidine (Pip) in dioxygen-free methylene chloride or nitrobenzene to form tetranuclear copper(I) complexes [(Pip)_nCuX]₄; n=1 or 2, X=Cl, Br or I. These complexes are very soluble and completely reduce dioxygen to dioxo bridging ligand, with stoichiometry, Δ[Cu(I)]/Δ[O₂]=4.0. The stable oxo solids [(Pip)_nCuX]₄O₂ mimic tyrosinase copper protein. They act as a homogeneous oxidative coupling catalysts for phenols. Electronic transition spectra in the near infrared with high molecular absorptivity are diagnostic for tetranuclear “Cu₄X₄” core structure. The electronic transitions are more likely due to charge transfer between a minimum of three halo ligands and copper(II) center. The room temperature EPR spectra of [(Pip)_nCuX]₄O₂ in methylene chloride are isotropic with four hyperfine lines. The room temperature solid-state EPR spectra of [PipCuX]₄O₂ show an axial spectra with d_x²−y² ground state, suggesting square pyramidal arrangement of the five coordinated ligands around copper(II) centers. Cyclic voltammetry measurements show that they are more likely irreversible in character and show slight quasi-reversability when X=Br or I. Constant potential electrolysis indicate that the number of electrons consumed are equal to four electrons which will be due to the reduction of four copper(II) to copper(I).     

An aluminoborate cluster [AlB12O14(OH)12]: Synthesis and structure of [C5H6N][AlB12O14(OH)12]

A new aluminoborate, [C₅H₆N][AlB₁₂O₁₄(OH)₁₂], has been hydrothermally synthesized at 200 °C. The single-crystal diffraction study reveals that it crystallizes in space group C2/c. It consists of aluminoborate clusters [AlB₁₂O₁₄(OH)₁₂]⁻ and counterions [C₅H₆N]⁺. The aluminoborate cluster contains an Al(OH)₆ octahedron as a core that is capped by two raft-like polyborate units [B₆O₇(OH)₆]. These clusters are further interlinked by extensive hydrogen bonding to form a three-dimensional (3D) network, containing large channels along the b-axis, in which the [C₅H₆N]⁺ cations are located.     

Resonance Raman and crystallographic studies on the complex [Fe2(bbpnol)2]·2DMF (bbpnol=N,N′-bis(2-hydroxybenzyl)-2-ol-1,3-propanediamine)

The ligand N,N′-bis(2-hydroxybenzyl)-2-ol-1,3-propanediamine (H₃bbpnol) reacts with iron(III) perchlorate forming two dinuclear bis-μ-alkoxo complexes, a ‘cis-trans’ isomer (complex 1) previously reported and a ‘cis-cis’ isomer (complex 2) characterized in this work. The main differences found in complex 2 structure are, (a) the four phenolic oxygens are trans to the alkoxo bridges; (b) each ligand is shared by the two Fe(III) ions occupying two coordination positions at each center. The Fe(III) centers in the resulting centrosymmetric structure in complex 2 have a distorted-octahedral geometry with the equatorial plane occupied by the phenolic and alcoholic oxygen atoms and the apical positions are filled by the aminic nitrogen atoms. The resonance Raman (RR) spectra of these two isomeric complexes are somewhat different with the intensity of some low-frequency modes increasing in the less symmetric core. The electronic spectra of both complexes are similar, but the molar absorptivities are substantially increased in complex 2, indicating the presence of an electronic coupling between the phenolate moieties trans in relation to the alkoxo bridge, and that phenolates coordinated cis to the alkoxo bridge do not seem to contribute to LMCT oscillator strength. This is directly reflected in the Raman excitation profiles (REP) of the chromophore modes, with the vibrational modes of the ‘cis-cis’ isomer showing a greater intensification compared with the ‘cis-trans’ isomer.     

Syntheses and X-ray structures of a series of V2S4(RCS2)4 (R=alkoxy, dialkylamino) complexes

A simple synthetic procedure leading to the V₂(S₂)₂(RCS₂)₄ species (R=Et₂N (1), cyclo-C₄H₈N (2), n-Bu₂N (3), EtO (4), i-PrO (5)) has been developed. X-ray structures of 3 and 5 have been reported, featuring the centrosymmetric molecules with VV distances 2.850(3) Å for 3 and 2.838(2) Å for 5.The FAB mass spectra were recorded. In all cases molecular peaks are observed. Fragmentation patterns are discussed.     

Theoretical studies on tetrahedral oxoanions MO4 (n=2, 3, 4; M=Cr, Mo, W)

The structure and bonding in MO₄ ⁿ⁻ (n=2, 3, 4; M=Cr, Mo, W) tetrahedral oxoanions have been investigated using density-functional methods. Good computational-experimental agreement for the geometrical parameters of the known species has been obtained which allowed the prediction of the cited parameters for those species that have not yet been isolated. The molecular-orbital analysis indicates that the chemical bonds mainly have d functions of the metal and p functions of oxygen. The electron affinities for the process MO₄ ⁿ⁻ + 1e → MO₄ ^(n + 1)− have also been calculated and their importance in relation with the preparation of the oxoanions MO₄ ⁿ⁻ (M=Mo, W; n=3, 4) not reported in the bibliography is discussed. Comparative studies of the electronic structures of oxoanions allow to explain their reactivities against nucleophilic and electrophilic attacks. The vibrational frequencies have been calculated and compared with the experimental values and the different relationships between the symmetric-stretching and antisymmetric-bending frequencies allow to confirm the assignations of the calculated spectra.     

Single molecule magnet: Heterodinuclear cyano-bridged cubic cluster [(Tp)8Fe4Ni4(CN)12] (Tp = hydrotris(1-pyrazolyl)borate)

The octanuclear cyano-bridged cluster [(Tp)₈Fe₄Ni₄(CN)₁₂] · H₂O · 24CH₃CN (1) (Tp = hydrotris(1-pyrazolyl)borate) showing magnetic properties of single-molecule magnet has been synthesized by reaction of [fac-Fe(Tp)(CN)₃]⁻ with {(Tp)Ni(NO₃)} species formed from an equimolar reaction mixture of Ni(NO₃)₂ · 6H₂O and KTp in MeCN. The X-ray analysis of 1 shows molecular cube structure in which Fe^III and Ni^II ions reside in alternate corners. The average intramolecular Fe?Ni distance is 5.124 Å. Out-of-phase ac susceptibility and reduce magnetization measurements show that 1 is a single molecule magnet with ground spin state S = 6 and spin reversal energy barrier U = 14 K. Magnetic hysteresis loops were also observed by applying fast sweeping field.     

Reactions of Zr(C5H5)(6,6-dmch)(PMe3)2 and Zr(6,6-dmch)2(PMe3)2 (dmch=dimethylcyclohexadienyl) with CO and alkynes

The reactions of Zr(C₅H₅)(6,6-dmch)(PMe₃)₂ and Zr(6,6-dmch)₂(PMe₃)₂ (dmch=dimethylcyclohexadienyl) with CO lead to the selective replacement of one PMe₃ ligand by CO. Both carbonyl complexes have been structurally characterized. Additionally, the reaction of the latter complex with PhC₂SiMe₃ leads to a similar replacement of one PMe₃ ligand, involving simple coordination of the alkyne, rather than any coupling to the dmch ligand.     

Identification ofS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptopyruvic acid with a metabolic intermediate betweenS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-l-cysteine andS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptolactic acid

Summary S-[2-Carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptopyruvic acid (I) was chemically synthesized in 15% yield by incubating a reaction mixture oftrans-urocanic acid and 3-fold excess of 3-mercaptopyruvic acid at 45°C for 6 days. The synthesized compound was characterized by fast-atom-bombardment mass spectrometry and high-voltage paper electrophoresis. CompoundI was identified with a product of an enzymatic reaction ofS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-l-cysteine (II) with rat liver homogenate in a phosphate buffer, pH 7.4. CompoundI was degraded toS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl]-3-mercaptolactic acid (III), a compound previously found in human urine [Kinuta et al. (1994) Biochem J 297: 475–478], by incubation with rat liver homogenate. From these results, we suggest that compoundI is a metabolic intermediate for the formation of compoundIII from compoundII. The present pathway follows a formation of compoundII fromS-[2-carboxy-1-(1H-imidazol-4-yl)ethyl] gluthathione [Kinuta et al. (1993) Biochim Biophys Acta 1157: 192–198], a proposed metabolite ofl-histidine.     

Chiroptical properties of heterotrimetallic ‘wing-tip’ butterflies; synthesis and crystal structure of (μ-H)Ru2Fe2PdC(CO)12 (η-ß-C10H15)

HRu₂Fe₂PdC(CO)₁₂ (η³-ß-C₁₀H₁₅) cluster was prepared in the reaction of (Et₄N) [HFe₂Ru₂C(CO)₁₂] with [Pd(η³-ß-C₁₀H₁₅)Cl]₂. X-ray structural study of HRu₂Fe₂PdC(CO)₁₂ (η³-ß-C₁₀H₁₅) (where ß-C₁₀H₁₅ is ß-pinenyl) revealed a wing-tip butterfly geometry of the metal core and (1R, 2S, 3S, 5R) absolute configuration for both crystallography independent molecules in the crystal. Chiroptical properties of this cluster are compared with other clusters containing a Pd(η³-ß-C₁₀H₁₅) fragment and discussed.