Speciation of dimethyltin(IV) – and trimethyltin(IV) – carbocysteinate and – glutamate systems in aqueous media

Abstract

The formation of complex species in the dimethyltin(IV) and trimethyltin(IV)-carboxymethyl-L-cysteinate (carbocysteinate) systems in NaCl_aq, at different ionic strengths, and in a multicomponent Na⁺, K⁺, Ca²⁺ ,Mg²⁺, Cl^? and SO₄^2-? medium representative of the seawater major composition, is discussed. Experimental results give evidence for the formation of the following species (L = carbocysteinate): [(CH₃)₂Sn(L)]⁰, [(CH₃)₂Sn(HL)]⁺, [(CH₃)₂Sn(OH)(L)]^?, [(CH₃)₂Sn(OH)₂(L)]^2? in the DMT–CCYS system, and [(CH₃)₃Sn(HL)]⁰, [(CH₃)₃Sn(L)]^? and [(CH₃)₃Sn(OH)(L)]^2? in the TMT-CCYS system. The ionic strength dependence of formation constants was taken into account by an extended Debye Hückel type equation and by the SIT (Specific ion Interaction Theory). Measurements were carried out also on the dimethyltin(IV)-glutamate and trimethyltin(IV)-glutamate systems in NaCl_aq, owing the strict similarity of glutamate and carbocysteinate. Results obtained show the formation of complex species having the same stoichiometry as those formed in the DMT- and TMT-carbocysteinate systems, with very similar stability, confirming that carbocysteinate behaves as a dicarboxylic amino acid without involving the sulfur-bridge potential binding site in metal coordination.     

Synthesis and spectral properties of Zr(IV) and Hf(IV) phthalocyanines with β-diketonates as axial ligands

The series of new zirconium(IV) and hafnium(IV) phthalocyanines with various β-dicarbonyl ligands were prepared via direct interaction between di(chloro)zirconium(IV) or hafnium(IV) phthalocyanines and free β-diketones and also with 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one. The structure of the obtained bis(β-dicarbonilato) zirconium(IV) and hafnium(IV) phthalocyanines was studied by two dimension ¹H NMR spectroscopy (COSY, NOESY, ROESY). Absorption and fluorescence spectroscopic studies have been investigated in various solvents. Analyzed compounds of concentration range below 10^?5 mol/dm³ do not aggregate in the organic solvents. Fluorescence quantum yields (Φ_F) and natural life times (τ) of zirconium phthalocyanine complexes have been calculated in toluene, DMSO and THF.     

Synthesis and characterization of tris(β-diketonato)technetium(III) and -(IV) complexes

The preparations and properties of tris(dipivaloylmethanato)technetium(III), tris(trifluoroacetylacetonato)technetium(III), and tris(hexafluoroacetonato)technetium(III) are described. The oxidation of the dipivaloyl derivative to tris(dipivaloyl)technetium(IV) hexafluorophosphate was shown to take place readily. Voltammetric studies and magnetic resonance results on the new complexes are reported. The large shifts observed for the complexes seem to be due to a contact interaction.     

Synthesis and structures of three,four, and six-coordinate monomeric tin(II) and tin(IV) compounds containing η2-ketiminate ligands

A series of Sn(II) and Sn(IV) compounds containing ketiminate ligands were synthesized. Reactions of SnCl₂ with 1 or 2 equiv. Li[OCMeCHCMeNAr] (where Ar = 2,6-diisopropylphenyl) generate [OCMeCHCMeNAr]SnCl (1) and [OCMeCHCMeNAr]₂Sn (2) in moderate yield, respectively. Similarly, reacting SnCl₄ with 2 equiv. Li[OCMeCHCMeNAr] yields a six-coordinated [OCMeCHCMeNAr]₂SnCl₂ (3). Divalent tin compound 2 can be oxidized with I₂ in diethyl ether to generate tetravalent tin compound [OCMeCHCMeNAr]₂SnI₂ (4) in moderate yield. Compounds 1–4 have been characterized by ¹H and ¹³C NMR spectroscopy and have been analyzed by X-ray crystallography. Theoretical calculation found that the bonding of ketiminate ligands and tin atom in compound 2 has a strong ionic character.     

Differential expression of ·1(IV), ·2(IV), ·5(IV) and ·6(IV) collagen chains in the basement membrane of basal cell carcinoma

Type IV collagen, the major component of basement membrane, consists primarily of ·1(IV) and ·2(IV) chains. Recently, other types of collagen IV chains, i.e. ·3(IV), ·4(IV), ·5(IV) and ·6(IV) chains, have been identified by protein chemistry and molecular cloning. We have examined the diversity of the assembly of ·(IV) chains of the basement membrane surrounding tumour nests of basal cell carcinomas, in tissues from 11 patients, by immunohistochemical analysis using specific monoclonal antibodies to six ·(IV) chain. The immunostaining profile of each chain differed with respect to the histological subtypes of basal cell carcinoma. In the morphea-like subtype, which was more invasive, ·1(IV) and ·2(IV) chains were discontinuously stained, and ·5(IV) and ·6(IV) chains were entirely absent. However, in the superficial subtype, which was non-aggressive, ·1(IV), ·2(IV), ·5(IV) and ·6(IV) chains were well stained compared with the other subtypes of basal cell carcinoma. In addition, in the solid subtype, which showed slow growth and ulceration, ·1(IV) and ·2(IV) chains were continuously stained, and ·5(IV) and ·6(IV) chains were discontinuous or absent. The assembly of ·5(IV) and ·6(IV) chains into the basement membrane was inhibited in the solid and morphea subtypes of BCC. This differential expression of type IV collagen chains seems to be associated with the invasive potential of basal cell carcinoma This revised version was published online in November 2006 with corrections to the Cover Date.     

Structural,infrared and Mössbauer studies of octahedral cis-dichlorobis(diketonate)tin(IV) complexes having anti-tumour activity

Two complexes, SnCl₂(bzac)₂ [Hbzac = benzoylacetone] and SnCl₂(bzbz)₂ [Hbzbz = dibenzoylmethane], have been prepared and characterised by analytical, infrared and Mössbauer studies. In addition, the X-ray crystal structure of SnCl₂(bzbz)₂ has been determined. The crystals are orthorhombic, space group Pbca with cell parameters a=18.767(9), b=17.611(8), c=16.563(8) Å. A total of 2116 reflections with I/σ(I)⩾3 gave R=3.0%. The tin is coordinated to two cis-chlorine and four oxygen atoms from the dibenzoylmethanato ligands in an approximately octahedral arrangement. The bond distances in the tin coordination sphere are SnCl 2.335(2) and 2.344(2) Å and SnO 2.062(4), 2.074(4), 2.063(4) and 2.063(4) Å and the ClSnCl angle is 95.1(1)°. The results of anti-tumour tests on these complexes are given and attempts are made to correlate the anti-tumour activity of SnCl₂(bzbz)₂ with its structure.     

Water-soluble titanocene complexes with sulfur-containing aminoacids: synthesis, spectroscopic, electrochemical and Ti(IV)–transferrin interaction studies

Three new water soluble titanocene–aminoacid complexes have been synthesized via the reaction of Cp₂TiCl₂ and two equivalents of aminoacid (L) in methanol, affording [Cp₂TiL₂]Cl₂, L=L-cysteine (2), D-penicillamine (3) and L-methionine (4). These complexes have been characterized by ¹H, IR and UV-Vis spectroscopies, elemental analysis and cyclic voltammetry. Kinetic studies of ligand hydrolysis have been monitored at low pH using UV-Vis and ¹H NMR spectroscopies to assess their stability in aqueous solution. At low pH, aminoacid ligands are lost one order of magnitude faster than cyclopentadienyl. However, at physiological pH, in Tris buffer solution, the complexes decompose rapidly to form an insoluble titanium compound. The affinity of these complexes to apo-transferrin was also investigated to elucidate how the ancillary aminoacid ligands affect the titanium intake by apo-transferrin.Electronic Supplementary Material Supplementary material is available for this article at     

Isomer distribution and structure of (2,2′-biphenyldiolato)bis(β-diketonato)titanium(IV) complexes: A single crystal X-ray, solution NMR and computational study

Novel dichlorobis(β-diketonato)titanium(IV) Ti(C₆H₅COCHCOR)₂Cl₂ and (2,2′-biphenyldiolato)bis(β-diketonato)titanium(IV) Ti(C₆H₅COCHCOR)₂biphen complexes with R = CH₃, C₆H₅ and CF₃, are synthesized and characterized by X-ray crystallography and further physical methods. There is a good agreement between DFT calculated and experimental structural data. A configurational analysis gives a calculated isomer distribution that is in agreement with the experimental data derived from low temperature ¹H NMR spectroscopy. The Ti(C₆H₅COCHCOR)₂biphen complexes exhibit high hydrolytic stability.     

A new hydroxo-bridged thorium(IV) dimer: Preparation and structure of di-μ-hydroxo-bis[aquanitrato(2,6-diacetylpyridinedisemicarbazone)thorium(IV)] nitrate tetrahydrate

The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Th(NO₃)₄ in ethanolwater mixture and a di-μ-hydroxo Th(IV) dimer is formed. The compound [Th₂(OH)₂(DAPSC)₂(NO₃)₂(H₂O)₂](NO₃)₄·4H₂O (I) is monoclinic, space group P2₁/n with a = 10.705(1), b = 19.008(2), c = 11.782(1) Å, β = 107.82(2)°, V = 2282(1) ų and Z = 2. Detailed X-ray structural analysis showed that each thorium atom in the complex is coordinated to one pentadentate DAPSC ligand, which is subjected to a considerable distortion, one bidentate nitrate group, one water ligand and two bridging hydroxo groups. The coordination number is ten and the best presentation of the polyhedron is that of a distorted bicapped square antiprism. The ThTh separation is 4.0181(6) Å and the average ThO(H) bridge is 2.366 Å. The structure was refined using 3185 reflections to an R value of 5.0%.     

Mono(maleonitriledithiolene)molybdenum(IV) and Bis(μ-sulfido)-Bridged Dimolybdenum(V) Complexes with MoS Moiety

Mono(maleonitriledithiolene)sulfidomolybdenum(IV) complex, [MoS(S(4) )(mnt)](2-) (2; mnt=maleonitriledithiolene) was synthesized by the substitution reaction of a tetrasulfido ligand of the known [MoS(S(4) )(2) ](2-) (1) upon reaction with one or even excess equivalent of Na(2) (mnt) in aqueous MeCN solution in air. Surprisingly, 2 undergoes dimerization on treatment with alkyl halide such as MeI and PhCH(2) Br to form bis(μ-sulfido)dimolybdenum(V) species, [{MoS(mnt)}(2) (μ-S)(2) ](2-) (3). These complexes have been characterized by IR, UV/VIS spectroscopy, cyclic voltammetry, elemental analysis, and by X-ray crystal-structure analysis. Differences in the relative stability and electrochemical behavior of 1, 2, and 3 have been correlated with theoretical calculations at DFT level.     

Metvan,bis(4,7-Dimethyl-1,10-phenanthroline)sulfatooxidovanadium(IV): DFT and Spectroscopic Study—Antitumor Action on Human Bone and Colorectal Cancer Cell Lines

The complex bis(4,7-dimethyl-1,10-phenantroline)sulfatooxidovanadium(IV), commonly known as Metvan, was prepared using a known synthetic procedure. Its optimized molecular structure was obtained by DFT calculations, as it was impossible to grow single crystals adequate for a crystallographic study. The complex was also characterized by a detailed analysis of its infrared spectrum, supported by the theoretical calculations, and also by some data derived from its Raman spectrum. In addition, cytotoxicity studies were performed using human osteosarcoma (MG-63) and human colorectal adenocarcinoma (HT-29) cell lines. The results show that Metvan impaired cell viability of both cancer cell lines in a low concentration range (0.25–5.0 μM).

     

Liver Transplantation in Man—IV,Haemorrhage and Thrombosis

Blood coagulation and fibrinolytic factors have been measured in 13 patients treated by liver transplantation. During operation intravascular coagulation and fibrinolysis were increased, but seldom to a degree which would cause abnormal bleeding. Measurement of the catabolism of radioactive fibrinogen showed that increased intravascular coagulation continued for long periods after the operation. Despite secondarily increased fibrinolysis, there was a high incidence of thrombosis. Treatment with anticoagulants or with fibrinolysis inhibitors may be valuable in these patients.     

Reactivity of platina-β-diketones towards chelating nitrogen and sulfur donors: formation of acyl(hydrido)platinum(IV) and acyl(chloro)platinum(II) complexes

The platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1) was found to react with chelating N,N-ligands 2(R^′NCR)C₅H₄N (R/R^′=Ph/OH, H/Ph, Me/Ph) to form acyl(hydrido)platinum(IV) complexes [Pt(COMe)₂Cl(H){2-(R^′NCR)C₅H₄N}] (R/R^′=Ph/OH 2a; H/Ph 2b; Me/Ph (2c)). Reactions of complex 1 with chelating S,S- and N,S-donors (RS-CH₂-CH₂-SR, 2-(RSCH₂)C₅H₄N, R=Et, Ph, t-Bu) afforded acyl(chloro)platinum(II) complexes [Pt(COMe)Cl(RSCH₂CH₂SR)] (R=Et, 3a; Ph, 3b; t-Bu, 3c) and [Pt(COMe)Cl{2-(RSCH₂)C₅H₄N}] (R=Et, 4a; Ph, 4b; t-Bu, 4c), respectively. All complexes were fully characterized by microanalysis, IR and NMR (¹H, ¹³C) spectroscopy. Furthermore, molecular structures of complexes 3b and 4b were determined by single-crystal X-ray diffraction analyses revealing close to square-planar configuration. In complex 4b the acetyl ligand is trans to pyridine N atom (configuration index SP-4-2). The reactions are discussed in terms of consecutive oxidative addition and reductive elimination reactions.     

Are diprotin A (Ile-Pro-Ile) and diprotin B (Val-Pro-Leu) inhibitors or substrates of dipeptidyl peptidase IV?

Dipeptidyl peptidase IV preferably hydrolyzes peptides and proteins with a penultimate proline residue. Umezawa and co-workers (Umezawa et al. (1984) J. Antibiotics 37, 422-425) reported that diprotin A (Ile-Pro-Ile) and diprotin B (Val-Pro-Leu) are inhibitors for dipeptidyl peptidase IV. We could show that both compounds as well as other tripeptides with a penultimate proline residue are substrates for dipeptidyl peptidase IV. An apparent competitive inhibition by those compounds is a kinetic artifact due to the substrate-like structure of such tripeptides.     

Total synthesis of (±)-elegansidiol, (±)-farnesiferol B,and (±)-farnesiferol D

The racemic total synthesis of elegansidiol, farnesiferol B, and farnesiferol D has been obtained following a Diels–Alder approach. Gillman addition, cross metathesis reaction are the other key steps involved in the target synthesis.     

Cobalt(II) and μ-oxodiiron(III,IV) complexes of salen analog with aromatic thioether pendant group,N, N′-disalicylidene-2-methyl-4-(2-methylthiophenyl)- 1,2-butanediamine

A pentadentate salen analog containing a thioether group in the pendant tail, N,N′-disalicylidene-2- methyl-4-(2-methylthiophenyl)- 1,2-butanediamine, has been synthesized. The cobalt(II) complex of this ligand retains a planar configuration free from the coordination of the pendant group at room temperature but adopts a square-pyramidal configuration with the thioether at the apex near liquid nitrogen temperature. The iron complex obtained with this ligand is shown to be a μ-oxodiiron(III, IV) complex comprised of high-spin iron(III) and low-spin iron(IV), based on cryomagnetic data (80–300 K), ESR, and M:ossbauer spectra. An antiferromagnetic spin-exchange interaction (J = − 13.0 cm ⁻¹) operates between the metal ions.