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PubMed2001

On the aromaticity of square planar Ga4(2-) and In4(2-) in gaseous NaGa4- and NaIn4- clusters.

We investigated the electronic structure and chemical bonding of two bimetallic clusters NaGa4- and NaIn4-. Photoelectron spectra of the anions were obtained and compared with ab initio calculations. We found that the ground state of the two anions contains a square planar dianion interacting with a Na+ cation. The Ga4(2-) and In4(2-) dianions both possess two delocalized pi electrons and are considered to be aromatic, similar to that recently found in Al4(2-). Using calculations for a model compound, we showed that a recently synthesized Ga4-organometallic compound also contains an aromatic -Ga4(2-)- unit, analogous to the gaseous clusters.

Journal Article↗
PubMed2002

Detection of organotin, organomercury, and organolead compounds with a pulsed discharge detector (PDD).

The response of a pulsed discharge detector (PDD) to organometallic compounds in the helium ionization detection (HID) mode was dependant on the number of C atoms in the tested analytes with the limits of detection ranging from 0.7 pg (tetraethyllead (Et(4)Pb)) to 1.2 pg di- n-propyl mercury (Pr(2)Hg)). Response linearity was excellent over three orders of magnitude. Selectivity in the HID mode was enhanced by doping the He discharge gas with argon, although sensitivity dropped threefold. In electron capture detection (ECD) mode, only organolead was detected with a limit of 0.1 pg.

Journal Article↗
PubMed2003

Parity-violation effects in the C-F stretching mode of heavy-atom methyl fluorides.

Relativistic four-component electronic structure calculations including parity-odd electroweak interactions give unprecedented large energy differences of 158 mHz for PH3AuCHFCl and 219 mHz for ClHgCHFCl for the C-F stretching mode of the corresponding enantiomeric compounds. This signifies a considerable improvement over previous predictions for chiral methyl compounds of the form CHXYZ (X, Y, Z=F, Cl, Br, or I). These organometallic compounds are therefore ideal for future high resolution spectroscopy experiments.

Journal Article↗
PubMed2006

Pressurized liquid extraction in environmental analysis.

A critical evaluation of recent literature utilizing pressurized liquid extraction (PLE) for environmental analysis is presented by compound class. Overall, the extraction efficiency of PLE, using the appropriate solvent, temperature and pressure for extraction, is similar to that of Soxhlet extraction. PLE has been used for some classes of compounds that are thermally labile (e.g., explosives) and may require acidic conditions for extraction (e.g., organometallic compounds). References to recent applications are presented emphasizing studies which utilize unspiked, natural matrices and studies that compare PLE to alternate extraction techniques.

Journal Article↗
PubMed2003

[Historical study of separation technology innovation in the field of pharmaceutical science].

The separation of organic compounds has been carried out using the method of distillation and recrystallization since the 17th century.1st separation technology innovation (1950s to 1960s). After World War II, the science of separating organic compounds evolved to the use of paper or column chromatography. 2nd separation technology innovation (1960s to 1980s). In the 1960s, thin-layer chromatograpy (TLC) was developed. TLC is a convenient analytical technique for organic compounds. Separation methods for organic compounds using column chromatography and preparative TLC were carried out as practical applications. Gas chromatography (GC) was also introduced in the 1960s. GC is a useful analytical method for a mixture of various volatile organic compounds. Many GC instruments with new kinds of sensors were developed. Gas chromatography of nonbenzenoid organometallic compounds and metal complexes was successfully conducted by the author. 3rd separation technology innovation (1980s to 1990s). In the 1980s, high-performance liquid-chromatography (HPLC) was developed. HPLC analytical methods were useful for various kinds of organic compounds. In the 1990s, LC-MS and LC-NMR instruments were introduced for biomedical products. 4th separation technology innovation (1990s to present). Several new ionization methods for mass-spectrometry (electrospray, matrix-aided lazer desorption ionization, etc) are applied for proteins and biomedical products. Several new separation technologies (supercritical field chromatography, capillary electrophoresis, field-flow fractionization, etc.) are now being developed.

History, 20th Century↗
PubMed2003

Organometallic chemistry of azuliporphyrins: synthesis, spectroscopy, electrochemistry, and structural characterization of nickel(II), palladium(II), and platinum(II) complexes of azuliporphyrins.

Four azuliporphyrins, two meso-unsubstituted and two meso-tetraaryl substituted, were investigated in the synthesis of novel organometallic compounds. The meso-unsubstituted or "etio" series azuliporphyrins 8 reacted with nickel(II) acetate, palladium(II) acetate, and platinum(II) chloride in DMF to give the corresponding chelates 14-16, where the metal cation lies within the macrocyclic cavity and binds to all three nitrogens and the internal carbon atom. The newly available meso-tetraarylazuliporphyrins 13 similarly afforded the corresponding nickel(II), palladium(II), and platinum(II) complexes, 17-19, respectively. The new organometallic complexes are stable nonpolar compounds and were fully characterized spectroscopically and by mass spectrometry. The UV-vis data indicate that these complexes, in common with the parent azuliporphyrin system 8, do not possess porphyrin-type aromaticity. However, electron donation from the azulene unit can give rise to dipolar resonance contributors that provide a degree of carbaporphyrin-type aromatic character. The platinum(II) azuliporphyrins 16 gave noteworthy proton NMR spectra where the meso-protons showed satellite peaks due to transannular coupling to platinum-195. The pyrrolic protons of the platinum(II) meso-tetraarylazuliporphyrin 19b also showed similar satellite peaks due to coupling from the platinum-195 isotope. The electrochemistry of free base tetraphenylazuliporphyrin 13a and the related nickel(II) and palladium(II) complexes was investigated using cyclic voltammetry, and these data indicate that metal coordination improves the reversibility of the ligand-based oxidations. Nickel(II) azuliporphyrin 14a and palladium(II) tetrakis(4-chlorophenyl)azuliporphyrin 18b were also structurally characterized by X-ray crystallography. The macrocyclic core of the palladium(II) complex 18b was significantly more planar than the nickel(II) derivative 14b, and this difference was attributed to the better size match between the azuliporphyrin cavity and the larger palladium(II) ion. The straightforward synthesis of metalloazuliporphyrins under mild conditions, and their interesting spectroscopic, electrochemical, and structural features, demonstrates that the azuliporphyrin system holds great promise as a platform for organometallic chemistry.

Journal Article↗
PubMed2001

Chemical instability and methods for measurement of cisplatin adducts formed by interactions with cysteine and glutathione.

Reactions between cisplatin or its aquated species and L-cysteine (L-cys) or glutathione (GSH) were studied in vitro using liquid chromatography on-line with inductively coupled plasma mass spectrometry (LC-ICPMS) and/or electrospray ionization mass spectrometry (LC-MS) in order to obtain information on the mechanisms occurring in treated patients. Reaction between cisplatin and L-cys yielded initially 4 adducts of which only 2 were stable and detectable after 24 hours incubation; their structures corresponded to bis-platinum cysteinyl adducts. Reaction of cisplatin with GSH proceeded via the formation of at least 11 glutathione-platinum adducts (G1 - G11) which underwent parallel reactions within 24 hours of incubation, probably to form higher molecular weight species. Of the 11 adducts, only 2, G3 and G7, whose structures correspond to [Pt(NH3)2Cl]2(SG) and [Pt(NH3)2OH]2(SG) were still present in the reaction mixture after 24 hours incubation. This study shows that GSH, and to a lesser extent L-cys, incubated with cisplatin in vitro forms unstable and reactive platinum compounds and that LC-ICPMS and LC-MS are 2 complementary techniques suitable for the study of organometallic compounds.

Antineoplastic Agents↗
PubMed1982

Off-line combination of liquid chromatography and field desorption mass spectrometry: principles and environmental, medical and pharmaceutical applications.

Field desorption mass spectrometry (FD-MS), which is applicable to analyses of compounds of low volatility and thermal instability, is used as a sensitive, specific and fast detection method for high-performance liquid chromatography (HPLC). Owing to its simplicity and efficiency, off-line combination is the preferred technique for the analysis of substances in chromatographic effuents. The principles of identification, purity control and quantification are presented. Characteristic examples of mental, medical and pharmaceutical areas are given. Qualitative and quantitative results for drugs and endogenous compounds, e.g., tranquillizers, immunosuppressive and antitumour agents and free amino acids, in human body fluids, biocides, e.g., phenylureas, carbamates, organophosphorus and organometallic compounds, in river water, and natural and synthetic products, e.g., saponins, chlorophyll and deoxyribonucleotides, are presented.

Barbiturates↗
PubMed2004

Decamethyldizincocene, a stable compound of Zn(I) with a Zn-Zn bond.

Unlike mercury, which has an extensive +1 oxidation state chemistry, zinc usually adopts the +2 oxidation state. Decamethyldizincocene, Zn2(eta5-C5Me5)2, an organometallic compound of Zn(I) formally derived from the dimetallic [Zn-Zn]2+ unit, has been isolated from the low-temperature (-10 degrees C) reaction of Zn(C5Me5)2 and Zn(C2H5)2 in diethyl ether. X-ray studies show that it contains two eclipsed Zn(eta5-C5Me5) fragments with a Zn-Zn distance (+/- standard deviation) of 2.305(+/-3) angstroms, indicative of a metal-metal bonding interaction.

Journal Article↗
PubMed2002

Organometallic Pt(II) compounds. A complementary study of a triplet emitter based on optical high-resolution and optically detected magnetic resonance spectroscopy.

The emitting triplet state of cyclometalated Pt(thpy)(CO)(Cl) monomers ((thpy)(-) = 2-(2'-thienylpyridinate), frequently also abbreviated as (2-thpy)(-)) is investigated at T = 1.2 K (typically) by use of the complementary methods of high-resolution optical spectroscopy and of optically detected magnetic resonance (ODMR) spectroscopy. Such a complimentary investigation is carried out for the first time for a Pt(II) compound. In solution, oligomer or short linear chain formation is also observed. However, the monomers can be investigated selectively, when they are dissolved in a relatively inert n-octane matrix (Shpol'skii matrix). This allows us to determine the energies of the T(1) triplet substates I, II, and III relative to the electronic ground state S(0)(0), the zero-field splittings (ZFSs) of T(1), and emission decay time constants (I/II <--> 0, 18012.5 cm(-1); III <--> 0, 18016.3 cm(-1); DeltaE(I,II) = 0.05437 cm(-1) (1.631 GHz), DeltaE(I,III) = 3.8 cm(-1) (114 GHz); tau(I) = 120 micros, tau(II) = 45 micros, tau(III) = 35 micros; spin-lattice relaxation time for the processes III --->I/II, tau(SLR) = 3.0 micros). The vibrational satellite structure observed in the emission of the T(1) state to the singlet ground state S(0) is also discussed. Moreover, it is possible to estimate the intersystem crossing time from the excited singlet state S(1) at 22952 cm(-1) to the triplet state T(1) to approximately 5 ps. The T(1) state is assigned as a thpy-ligand-centered (3)pipi* state with small metal-to-ligand charge-transfer (MLCT) admixtures. A comparison of Pt(thpy)(CO)(Cl) to a series of other organometallic Pt(II) compounds, such as heteroleptic Pt(ppy)(CO)(Cl) ((ppy)(-) = phenylpyridinate), Pt(dppy)(CO) ((dppy)(2-) = diphenylpyridinate), and Pt(i-biq)(CN)(2) (i-biq = 2,2'-bisisoquinoline) and homoleptic Pt(thpy)(2) and Pt(ppy)(2), is carried out. (The structures are shown in Figure 7.) Trends of photophysical properties are discussed. In particular, by chelation of two equal ligands the pattern of ZFS is strongly altered, resulting in a significant increase of the MLCT participation in the lowest triplet state of these organometallic compounds. This new observation represents an interesting further step concerning chemical tunability of photophysical properties.

Journal Article↗
PubMed1979

Lymphocytotoxicity and immunosuppression by organotin compounds. Suppression of graft-versus-host reactivity, blast transformation, and E-rosette formation by di-n-butyltindichloride and di-n-octyltindichloride.

Di-n-butyltindichloride (DBTC) and di-n-octyltindichloride (DOTC) represent a new group of organometallic compounds with antilymphocytic properties. In rats they induce lymphocyte depletion in thymus and thymus-dependent areas of spleen and peripheral lymph nodes without signs of myelotoxicity or a generalized toxicity. The number and viability of cells isolated from thymus and peripheral lymphoid organs was severely decreased, whereas the number and viability of bone marrow cells was not reduced. Immunosuppressive properties of DBTC and DOTC are indicated, in this study, by a severe decrease of the graft-versus-host response and the response to the T-cell mitogens phytohemagglutinin and concanavalin A. The T-cell selectivity of these compounds is discussed. In vitro DBTC and DTOC are extremely cytotoxic. Blast transformation of human as well as rat thymocytes was already inhibited at concentrations as low as 0.02 micrograms DBTC (or 0.1 micrograms DOTC) ml medium. Also the E-rosette formation was inhibited at very low drug levels. The similarity of effects upon rat and human lymphocytes suggests that DBTC and DOTC acts in the same manner in rat and man and offers the possibility of a therapeutic use of these compounds.

Animals↗
PubMed1996

Gas generation and preconcentration coupled to gas phase molecular absorption spectrometry: a powerful tool for the simultaneous determination of analytes forming volatile compounds.

Different methods for a simultaneous determination of several analytes forming volatile compounds at room temperature are described. The main steps of these methods are: continuous generation, collection in a cryogenic trap, revolatilization, measurement of the volatile compounds by Gas Phase Molecular Absorption Spectrometry and resolution by multi-wavelength methods. Several mixtures containing 2, 3 or 4 components have been studied: 1) elements forming covalent hydrides; 2) arsenic organometallic compounds forming volatile gases with a similar structure to arsine; and 3) sulphur species that can evolve volatile compounds. Under the optimum conditions obtained for each mixture, detection limits range from 0.8 ng/mL (dimethylarsinic acid) to 2 microg/mL (SCN(-)).

Journal Article↗
PubMedDate not supplied

Four decades of joy in mass spectrometry.

Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career.

Journal Article↗
PubMed2005

The 2 x 3 toolbox of organometallic methods for regiochemically exhaustive functionalization.

This review describes a concept aimed at rational and maximal structure proliferation. To this end, simple aromatic or heterocyclic starting materials, often bulk chemicals, are converted into all regionisomerically possible polar organometallic intermediates (mostly lithiated species), which then may be combined with any of the countless electrophiles to provide attractive new building blocks, particularly functionalized derivatives. The practical implementation relies on a set ("toolbox") of sophisticated recipes developed by mechanistically guided modification of the two most prominent exchange methods used for the generation of polar organometallic compounds: hydrogen-metal and halogen-metal interconversion. These mutant methods ("old methods in a new outfit") amplify the existing options for organic synthesis by ensuring maximum regioflexibility. At the same time they offer new insight into factors that govern organometallic reactivity and provide hints on how to alter or finetune this reactivity judiciously.

Journal Article↗
PubMed2003

Synthetic, reactivity, and structural studies on half-sandwich (eta5-C5Me5)Be and related compounds: halide, alkyl, and iminoacyl derivatives.

The half-sandwich compounds [(eta(5)-C(5)Me(5))BeX] (X=Cl, 1 a; Br, 1 b), readily prepared from the reaction of the halides BeX(2) and M[C(5)Me(5)] (M=Na or K), are useful synthons for other (eta(5)-C(5)Me(5))Be organometallic compounds, including the alkyl derivatives [(eta(5)-C(5)Me(5))BeR] (R=Me, 2 a; CMe(3), 2 b; CH(2)CMe(3), 2 c; CH(2)Ph, 2 d). The latter compounds can be obtained by metathetical exchange of the halides 1 with the corresponding lithium reagent and exhibit NMR signals and other properties in accord with the proposed formulation. Attempts to make [(eta(5)-C(5)Me(5))BeH] have proved fruitless, probably due to instability of the hydride toward disproportionation into [Be(C(5)Me(5))(2)] and BeH(2). The half-sandwich iminoacyl [(eta(5)-C(5)Me(5))Be(C(NXyl)Cp')] and [(eta(5)-C(5)Me(4)H)Be(C(NXyl)Cp')]3, 6 where Xyl=C(6)H(3)-2,6-Me(2) and Cp'=C(5)Me(5) or C(5)Me(4)H, are formed when the beryllocenes [Be(C(5)Me(5))(2)], [Be(C(5)Me(4)H)(2)], and [Be(C(5)Me(5))(C(5)Me(4)H)] are allowed to react with CNXyl. Isolation of three different iminoacyl isomers from the reaction of the mixed-ring beryllocene [(eta(5)-C(5)Me(5))Be(eta(1)-C(5)Me(4)H)] and CNXyl, namely compounds 5 a, 5 b, and 6, provides compelling evidence for the existence in solution of different beryllocene isomers, generated in the course of two very facile processes that explain the solution dynamics of these metallocenes, that is the 1,5-sigmatropic shift of the Be(eta(5)-Cp') unit around the periphery of the eta(1)-Cp' ring, and the molecular inversion rearrangement that exchanges the roles of the two rings.

Journal Article↗
PubMed1999

Aqueous Organometallic Chemistry of Ruthenium(II). Aquo Carbonyl Derivatives and Related Ethene Hydrocarboxylation in Fully Aqueous Solvent.

A series of new water soluble and stable organometallic compounds is reported, and the peculiar role of water in their formation and stabilization is documented together with their catalytic properties in aqueous solution. The complex fac-Ru(OCOCF(3))(2)(CO)(3)(H(2)O) (1) constitutes the entry to a new type of aqueous organometallic chemistry. The substitution of trifluoroacetato ligands by H(2)O yields [fac-Ru(CO)(3)(H(2)O)(3)](2+) (2), isolated as the tetrafluoroborate derivative, the first structurally characterized complex bearing CO and H(2)O ligands only. In water, 2 undergoes nucleophilic attack by the solvent yielding [fac-Ru(COOH)(CO)(2)(H(2)O)(3)](+) (3), followed by CO(2) elimination to give [fac-RuH(CO)(2)(H(2)O)(3)](+) (4), a ruthenium(II) hydride devoid of group-15-donor coligands and stable toward strong acids. 4 inserts ethene in water to give [fac-Ru(C(2)H(5))(CO)(2)(H(2)O)(3)](+) (5), an exceptionally inert alkyl complex which inserts CO yielding [fac-Ru(C(O)C(2)H(5))(CO)(2)(H(2)O)(3)](+) (6). Attempts to isolate the mononuclear cationic acyl complex gave the tetranuclear Ru(4)(C(O)C(2)H(5))(4)(OH)(2)(CF(3)SO(3))(2)(CO)(8) (7). At 140 degrees C the mononuclear organometallic complexes become labile intermediates of a Reppe hydrocarboxylation of ethene in fully aqueous solvent.

Journal Article↗
PubMedDate not supplied

Determination of McGowan volumes for ions and correlation with van der Waals volumes.

The McGowan volume has been widely used for the analysis of physicochemical and biochemical properties in chemistry and drug industry. Because McGowan volumes are not available for ions, its application is limited to only neutral compounds. Pauling radii of metallic ions have been collected and studied to obtain McGowan volumes for ions. Regression analysis was carried out between Pauling radii (R(p)) and McGowan radii (R(x)) for a wide range of compounds. It was found that Pauling radii and McGowan radii derived from McGowan volumes by using a volume-radius formula are linearly related (R(x) = 1.115R(p) + 0.0623, r(2) = 0.995). This equation is then used to calculate McGowan volumes for various ions and charged groups. McGowan volumes have been calculated for inorganic, organic, and organometallic compounds and correlated with van der Waals volumes. Results show that McGowan volumes (V(x)) are entirely equivalent to computer-calculated van der Waals volumes.

Journal Article↗
PubMed1997

Determination of trace amounts of vanadyl porphyrin in marine mussel tissues by high-performance liquid chromatography with both ultraviolet/visible and inductively coupled plasma atomic emission spectrometric detection.

An HPLC method with UV/VIS and ICP-AES detection is described for the determination of vanadyl porphyrins extracted from biological samples. A detection limit of 50 ng of vanadium was obtained. The method was used to determine these compounds following their extraction from tissues of mussels treated in laboratory experiments and collected during a 'Mussel Watch Programme'. This allowed some conclusions about vanadium speciation in marine organisms to be made. In the tissues of mussels, collected at several sites of the monitored area, which showed high vanadium concentrations, it was possible to establish the presence of this metal in the form of organometallic compounds.

Animals↗