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PubMed2002

Selective transformations of organic compounds by imidozirconocene complexes.

Imidozirconocene complexes (Cp(2)Zr=NR(THF)) possess a rich reaction chemistry, in contrast to many imido complexes of later transition metals. The synthesis and structural characteristics of these compounds are briefly described, along with a qualitative molecular orbital description of the metallocene-imido interaction. Imidozirconocene complexes react at the Zr=N linkage with a variety of X-H bonds, and undergo overall [2 + 2] cycloaddition reactions with a wide range of unsaturated organic and organometallic compounds. Results of studies detailing the scope and mechanism of these reactions are presented herein, along with applications to catalytic hydroamination, imine metathesis, and asymmetric transformations.

Alkenes↗
PubMed1987

[Cytostatic non-platinum metal complexes: new perspectives for the treatment of cancer?].

Non-platinum-group metal antitumor agents are represented by inorganic and organometallic compounds which contain either main-group metals such as gallium, germanium, and tin, or transition metals such as titanium, vanadium, iron, copper, and gold. Their antiproliferative properties have been detected during the past years, the spectrum of antitumor activity not being identical with that of cytostatic platinum complexes. In the case of germanium complexes, the antitumor activity is obviously not based on direct cytotoxic effects, but on host-mediated immunopotentiating mechanisms. The toxic properties of most non-platinum-group metal antitumor agents differ fundamentally from those of platinum compounds. Thus, non-platinum-group metal antitumor agents may open new perspectives for the clinical therapy of human malignancies.

Animals↗
PubMed2005

Metalloporphyrin-NO bonding: building bridges with organometallic chemistry.

DFT calculations in our laboratory and elsewhere have elucidated fundamental aspects of the structure and bonding of a variety of metalloporphyrin-diatomic complexes, including the biologically important heme CO, NO, and O(2) complexes. We have also studied some more exotic species such as metalloporphyrin-dinitrosyl, -dialkyl, and -diaryl complexes. In the course of this research, we discovered a number of unexpected similarities (isolobal analogies) between the bonding in metalloporphyrin-NO and organometallic compounds. Equally important, DFT calculations have played a significant role in advancing our understanding of selective diatomic ligand binding by heme proteins.

Hemeproteins↗
PubMed2005

Controlling ligand substitution reactions of organometallic complexes: tuning cancer cell cytotoxicity.

Organometallic compounds offer broad scope for the design of therapeutic agents, but this avenue has yet to be widely explored. A key concept in the design of anticancer complexes is optimization of chemical reactivity to allow facile attack on the target site (e.g., DNA) yet avoid attack on other sites associated with unwanted side effects. Here, we consider how this result can be achieved for monofunctional "piano-stool" ruthenium(II) arene complexes of the type [(eta6-arene)Ru(ethylenediamine)(X)]n+. A potentially important activation mechanism for reactions with biomolecules is hydrolysis. Density functional calculations suggested that aquation (substitution of X by H2O) occurs by means of a concerted ligand interchange mechanism. We studied the kinetics and equilibria for hydrolysis of 21 complexes, containing, as X, halides and pseudohalides, pyridine (py) derivatives, and a thiolate, together with benzene (bz) or a substituted bz as arene, using UV-visible spectroscopy, HPLC, and electrospray MS. The x-ray structures of six complexes are reported. In general, complexes that hydrolyze either rapidly {e.g., X = halide [arene = hexamethylbenzene (hmb)]} or moderately slowly [e.g., X = azide, dichloropyridine (arene = hmb)] are active toward A2780 human ovarian cancer cells, whereas complexes that do not aquate (e.g., X = py) are inactive. An intriguing exception is the X = thiophenolate complex, which undergoes little hydrolysis and appears to be activated by a different mechanism. The ability to tune the chemical reactivity of this class of organometallic ruthenium arene compounds should be useful in optimizing their design as anticancer agents.

Antineoplastic Agents↗
PubMed2002

Speciation of lead in environmental waters by preconcentration on a new fullerene derivative.

A novel fullerene derivative including a chelating group attached to the fullerene core has been prepared by photoreaction of C60 and sodium diethyldithiocarbamate (NaDDC) in toluene-methanol medium. The optimization of the synthesis procedure was monitored by UV-visible spectroscopy using the spectrum of C60 fullerene as reference; the new material, a C60-NaDDC monoadduct, showed a shoulder at 430 nm and an increase in the absorption band comprised between 425 and 500 nm. The solid was obtained by photolysis reaction in approximately 24 h, requiring further purification by preparative chromatography. Characterization of the brown product was accomplished by XRD and solid-state 13C MAS NMR; chemical modification was confirmed through the appearance of peaks close to the fullerene core peak located at 146.9 ppm, which can be assigned to carbon atoms of C60 that are covalently bonded to the diethyldithiocarbamate group to form a pyrrolidine ring-fused fullerene monoadduct. Using lead species as a model assessed the ability of the new material for the preconcentration of metallic and organometallic compounds, providing detection limits of 4-15 ng/L. The most interesting conclusions of the results were high adsorption efficiency, selectivity, and stability of the C60-NaDDC derivative (the packed material can be used for at least six months).

Fullerenes↗
PubMed1993

Titanocendichloride activity in cisplatin and doxorubicin-resistant human ovarian carcinoma cell lines.

The activity of a new organometallic compound, titanocendichloride, was evaluated in doxorubicin- and cisplatin-resistant human ovarian carcinoma cell lines in vitro. Titanocendichloride showed no cross resistance to doxorubicin in two multidrug resistant sublines of A2780. Furthermore, the cell line A2780 CP3, which is about 20-fold resistant to cisplatin was only 2.5-fold resistant to titanocendichloride, indicating a lack of cross resistance between the two metal compounds. These results were confirmed in vivo where titanocendichloride showed a much stronger inhibitory effect in cisplatin-resistant human ovarian carcinoma xenografts than cisplatin.

Animals↗
PubMed2003

An extensible and systematic force field, ESFF, for molecular modeling of organic, inorganic, and organometallic systems.

ESFF is a rule-based force field designed for modeling organic, inorganic, and organometallic systems. To cover this broad range of molecular systems, ESFF was developed in an extensible and systematic manner. Several unique features were introduced including pseudoangle and a dot product function representing torsion energy terms. The partial atomic charges that are topology-dependent are determined from ab initio (DFT) calculated electronegativity and hardness for valence orbitals. The van der Waals parameters are charge-dependent, and correlated with the ionization potential for atoms in various valence states. To obtain a set of well-defined and physically meaningful parameters, ESFF employs semiempirical rules to translate atomic-based parameters to parameters typically associated with a covalent valence force field. The atomic parameters depend not only on atom type, but also on internal type, thus resulting in a more accurate force field. This article presents the theory and the method used to develop the force field. The force field has been applied to molecular simulations of a wide variety of systems including nucleic acids, peptides, hydrocarbons, porphyrins, transition metal complexes, zeolites, and organometallic compounds. Agreement with the experimental results indicates that ESFF is a valuable tool in molecular simulations for understanding and predicting both crystal and gas phase molecular structures.

Algorithms↗
PubMed2002

Addition of organocerium reagents to morpholine amides: synthesis of important pheromone components of Achaea janata.

Readily preparable morpholine amides hitch in good yields with organocerium reagents to produce ketones. Even in the presence of substrates and reagents with high steric hindrance, the organometallic compounds prepared from dry cerium(III) chloride and organomagnesium or organolithium compounds at -78 degrees C add cleanly to morpholine amides. The low cost of starting materials makes this new scheme of synthesis very interesting for the preparation of biologically important pheromones.

Amides↗
PubMed2002

Topoisomerase II antagonism and anticancer activity of coordinated derivatives of [RuCl(2)(C(6)H(6))(dmso)].

Topoisomerase II poisoning and anticancer activity by the organometallic compound [RuCl(2)(C(6)H(6))(dmso)] was shown by us in an earlier study [Biochemistry 38 (1999) 4382]. Since high concentrations of this complex were required to achieve either effects, we have synthesized four derivatives of this complex in which the dimethyl sulphoxide group on the ruthenium atom was replaced with pyridine, 3-aminopyridine, p-aminobenzoic acid, and aminoguanidine. Three of these molecules showed enhanced potency of topoisomerase II poisoning and consequently also showed higher anticancer activity in breast and colon carcinoma cells in vitro. Detailed analysis of the molecular action of these compounds on topoisomerase II activity was carried out using the classical relaxation and cleavage activity of the enzyme, which revealed that the compounds poison topoisomerase II by freezing the enzyme and enzyme-cleaved DNA in a ternary "cleavage complex". The cleavage complex is implicated in the anti-neoplastic activity of these compounds. DNA interaction studies showed that these compounds interact with DNA in much the same way as [RuCl(2)(C(6)H(6))(dmso)], by external binding of the DNA helix. This is unlike most other topoisomerase II poisons, which predominantly interact with DNA through intercalation with the double helix.

Animals↗
PubMedDate not supplied

Antitumor activity of titanocene dichloride in xenografted human renal-cell carcinoma.

Titanocene dichloride [(C5H5)2TiCl2] is a new-developed organometallic antitumor agent which is currently being investigated in clinical trials of phases I and II. In the present study, it was tested for antitumor activity in human renal tumors either growing as monolayers in vitro or as xenografts in athymic mice. For comparison, approved cytostatic drugs (in vitro, vinblastine and 5-fluoro-2'-deoxyuridine; in vivo, cyclophosphamide, vinblastine, and 5-fluorouracil) were administered in vitro and in vivo at equivalent or equitoxic dose levels, respectively. Under in vitro conditions, titanocene dichloride was active only moderately. When it was applied at peak plasma level of 10(4) mol/l, it induced cell growth inhibitions by 25-50% in all KTCTL cell lines investigated (KTCTL-1M, KTCTL-2, KTCTL-26A, KTCTL-30, KTCTL-84). In the N-U 2 carcinoma cell strain it was more effective and caused cell growth inhibitions of 70-80% at the 10(-4) mol/l level, the IC50 value amounting to 5 x 10(-6) mol/l. When titanocene dichloride was applied intraperitoneally (i.p.) according to the Q3Dx5 and Q2Dx5 regimens and investigated in the human renal-cell carcinoma N-U 2 growing as xenograft in athymic mice, it brought about significant and dose-dependent growth reductions by 50-75% in relation to untreated controls, whereas cyclophosphamide given as single bolus injection and vinblastine administered both as single and triple doses were slightly less effective in this xenograft. MKT 4 and MKT 5, two formulations of titanocene dichloride which are currently used in clinical trials, showed similar efficacy as titanocene dichloride towards the N-U 2 renal-cell carcinoma xenograft. In the heterotransplanted N-U 26 carcinoma, titanocene dichloride induced relative growth reductions by 50-56% and was similarly active as cyclophosphamide, but less effective than vinblastine applied as a single dose. Titanocene dichloride was again significantly active in the KTCTL-1M carcinoma xenograft and caused relative growth reductions by 50-65%. In the case of the MRI-H 121 renal sarcoma xenograft, however, the organometallic compound showed an only marginal activity which was surpassed by cyclophosphamide, vinblastine and 5-fluorouracil, all three drugs inducing significant relative growth inhibitions by 50-88%. These results confirm a significant and remarkable antitumor activity of titanocene dichloride in three out of four human renal tumors xenografted to athymic mice and suggest that clinical studies of phase II with titanocene dichloride towards renal-cell carcinoma in human patients should be done in the near future.

Animals↗
PubMed2007

Organometallics meet colloid chemistry: a case study in three phases based on molecular carbonyl precursors containing zinc and manganese.

Two organometallic compounds containing zinc and manganese in different ratios are used as single-source precursors for the preparation of various new, bimetallic oxide materials with nanoscaled dimensions. It is shown that the materials synthesis can be performed in the solid-state, the liquid-phase, and even in the gas-phase. The molecular composition of the precursors determines the composition of the resulting materials. In addition, two novel methods for the preparation of highly crystalline metal oxide colloids are presented: The coupling between a gas-phase process and a colloidal approach, and the application of ozone as an oxidant for the transformation of metal carbonyls into oxides in the liquid phase.

Carbon Monoxide↗
PubMed2005

P-S Bond scission by bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp(2)MoCl(2)(aq): first documented example of an organometallic complex hydrolyzing thiophosphinates.

Thiophosphinate hydrolysis involving P-S bond scission is desirable for the degradation of organophosphate neurotoxins, and we report the first case for such a hydrolytic process by an organometallic compound. The metallocene, bis(cyclopentadienyl)molybdenum(IV) dichloride, Cp(2)MoCl(2) (Cp = eta(5)-C(5)H(5)), hydrolyzes a variety of thioaryl diphenylphosphinates in an aqueous THF solution. P-S scission of p-methoxythiophenyl diphenylphosphinate has a 500-fold rate of acceleration in the presence of Cp(2)MoCl(2)(aq) with activation parameters of 20(3) kcal mol(-)(1) and -15(3) cal mol(-)(1) K(-)(1) for DeltaH(double dagger) and DeltaS(double dagger), respectively. These activation parameters and the rate acceleration are consistent with an intermolecular hydrolytic process in which the Cp(2)Mo serves as a Lewis acid to activate the phosphinate for nucleophilic attack. Furthermore, rho = 2.3 (25 degrees C) which indicates a single nonconcerted mechanism in which the rate determining step is the nucleophilic attack on the activated phosphinate.

Crystallography, X-Ray↗
PubMed1984

Isolation of serum protein organometallic corrosion products from 316LSS and HS-21 in vitro and in vivo.

An investigation into blood-borne organometallic compounds that arise from the corrosion of metals used in orthopedic prosthetic devices was conducted using an in vivo rat model with an implantation time of 10 days and an in vitro human serum model with an incubation time of 5 days. Both models involved 316LSS and HS-21 in the spherical powder form of 55 +/- 5 microns microns in diameter at three different surface areas to body weight ratios. Gel chromatography on cross-linked dextran (G-200) was used to fractionate the serum proteins which bound the metal ions (chromium, cobalt, and nickel) released and identify them. Atomic absorption-spectrophotometry analysis measured the concentration of the metal ions in each serum protein peak as well as whole serum from both models, and red cell and tissue from the in vivo model. Within the serum proteins, the metal ions were bound to two of the principal serum protein peaks. Similar distributions of the metals among the serum protein peaks were not noted.

Alloys↗
PubMed2003

Reactions of gold(III) complexes with serum albumin.

The reactions of a few representative gold(III) complexes -[Au(ethylenediamine)2]Cl3, [Au(diethylentriamine)Cl]Cl2, [Au(1,4,8,11-tetraazacyclotetradecane)](ClO4)2Cl, [Au(2,2',2'-terpyridine)Cl]Cl2, [Au(2,2'-bipyridine)(OH)2][PF6] and the organometallic compound [Au(6-(1,1-dimethylbenzyl)-2,2'-bipyridine-H)(OH)][PF6]- with BSA were investigated by the joint use of various spectroscopic methods and separation techniques. Weak metal-protein interactions were revealed for the [Au(ethylenediamine)2]3+ and [Au(1,4,8,11-tetraazacyclotetradecane)]3+ species, whereas progressive reduction of the gold(III) centre was observed in the cases of [Au(2,2'-bipyridine)(OH)2]+ and [Au(2,2',2'-terpyridine)Cl]2+. In contrast, tight metal-protein adducts are formed when BSA is reacted with either [Au(diethylentriamine)Cl]2+ and [Au(6-(1,1-dimethylbenzyl)-2,2'-bipyridine-H)(OH)]+. Notably, binding of the latter complex to serum albumin results in the appearance of characteristic CD bands in the visible spectrum. It is suggested that adduct formation for both of these gold(III) complexes occurs through coordination at the level of surface histidines. Stability of these gold(III) complexes/serum albumin adducts was tested under physiologically relevant conditions and found to be appreciable. Metal binding to the protein is tight; complete detachment of the metal from the protein has been achieved only after the addition of excess potassium cyanide. The implications of the present results for the pharmacological activity of these novel cytotoxic agents are discussed.

Animals↗
PubMed2006

Pulmonary response to methylcyclopentadienyl manganese tricarbonyl treatment in rats: injury and repair evaluation.

Methylcyclopentadienyl manganese tricarbonyl (MMT), an organometallic compound, used as an antiknock additive in fuels, may produce alveolar inflammation and bronchiolar cell injury. The aim of the experimental study on female rats was to determine by morphological examination and sensitive biomarkers, the course of the injury and repair process following a single i.p. injection of 5 mg/kg MMT. The animals were sacrificed 12, 24, 48 hours or 7 days post-exposure (PE). The first biochemical changes 12 h PE showed an increase in GSH-S-transferase (GST) activity in the lung parallel to the earliest observed morphological changes -vacuolation and swollen cytoplasm in type I pneumocytes. Alterations in type I pneumocytes were most prevalent in rat lung 24 h PE. Clara cells with dilated smooth endoplasmic reticulum membranes and cytoplasmic vacuolation could be observed. Compared to the values found for controls, Clara cell protein (CC16) in the bronchoalveolar lavage fluid (BALF) at 24 and 48 h PE decreased by 58% and 55%, respectively. At the same time (at 24 and 48 h), the total protein concentration in BALF increased 5 and 7 times, respectively. A significant rise in hyaluronic acid (HA) level was observed 24 and 48 h PE. Divided type II pneumocyte cells and Clara cells in their mitotic phase were observed in immunocytochemistry (detecting BrdU binding into DNA) 48 h PE. Seven days after MMT administration, fibroblasts, macrophages, collagen and elastin fibres could be seen in the alveolar walls as well as neutrophils, lymphocytes, and alveoli macrophages in the alveolar lumen. We conclude that injury and repair of bronchial epithelium cells, especially of Clara cells and type II pneumocyte cells, play an important part in MMT toxicity, probably depending on the antioxidant status of these cells. The sensitive biomarkers of CC16 and hyaluronic acid in BALF and serum reflect lung injury and indicate the time course of pulmonary damage and repair processes.

Animals↗
PubMed2005

Interaction of molybdocene dichloride with cysteine-containing peptides: coordination, regioselective hydrolysis, and intramolecular aminolysis.

Reactions of the organometallic compound molybdocene dichloride (Cp2MoCl2, Cp = eta5-cyclopentadienyl) with the cysteine-containing peptides L-cysteinylglycine (Cys-Gly), N-acetyl-L-cysteine (AcCys), glycyl-L-cysteine (Gly-Cys), glycyl-L-cysteinylglycine (Gly-Cys-Gly), and gamma-L-glutamyl-L-cysteinylglycine (glutathione, GSH) have been studied in aqueous solution in the pH range 2-9. The dipeptides Cys-Gly and Gly-Cys and the acetylated amino acid AcCys form 1:1 and 2:1 complexes of composition [Cp2Mo(peptide-S)(OH(2))]n+/- and [Cp2Mo(peptide-S)2]n+/- as well as the chelates [Cp2Mo(AcCys-S,O)], [Cp2Mo(Gly-Cys-S,O)]+, and [Cp2Mo(Cys-Gly-S,N)] with the Cp2Mo2+ unit binding to the deprotonated thiolate group and the free amino or carboxylate group of the cysteine residue. Upon treatment of Gly-Cys-Gly and the naturally occurring tripeptide GSH with Cp2MoCl2 at elevated temperature, release of free glycine was observed. The Cp2Mo2+ entity coordinates to the thiolate group of GSH and mediates regioselective hydrolysis of the Cys-Gly peptide bond by intramolecular metal hydroxide activation. Cp2Mo2+-promoted hydrolysis of GSH was followed at pD 7.4 and 5.2 and 40 and 60 degrees C. By contrast, the Cys-Gly bond in [Cp2Mo(Gly-Cys-Gly-S,N)] is cleaved by intramolecular aminolysis at pD > or = 7.4 and 60 degrees C leading to glycine and the Cp2Mo2+ complex of the 2,5-diketopiperazine derivative cyclo-(Gly-Cys). Chelating coordination of the Cp2Mo2+ moiety to the thiolate group and to the deprotonated amide nitrogen of the tripeptide changes the configuration of the peptide bond from (preferred) trans to cis, thus enabling nucleophilic attack of the primary amino group at the Cys-Gly bond. The reaction product [Cp2Mo{cyclo-(Gly-Cys)}] x 2H2O has been characterized by X-ray crystallography.

Amides↗
PubMed1982

Biospecific labeling with undecagold: visualization of the biotin-binding site on avidin.

The biotin-binding site on avidin has been labeled with biotin conjugated to undecagold, an organometallic cluster compound containing 11 gold atoms in a core angestroms in diameter. Examination of unstained specimens by scanning transmission electron microscopy reveals the labeled sites directly, without computational averaging or filtering of the images. This approach should be widely applicable for determining the locations of subunits and functional site in biological macromolecules at a resolution at a resolution in range of 15 angstroms.

Avidin↗