Synthesis of terminal uranium(IV) disulfido and diselenido compounds by activation of elemental sulfur and selenium.

Rare stakes: Terminal uranium(IV) disulfido and diselenido compounds, Tp*2U(E2) (E=S, Se), were synthesized by the activation of elemental chalcogens. Structural, spectroscopic, computational and magnetic studies of these species establish their tetravalency and highly polarized U-E bonds.

A simple synthesis of APM ([p-(N-acrylamino)-phenyl]mercuric chloride), a useful tool for the analysis of thiolated biomolecules.

This study describes two novel synthetic procedures to prepare APM, a useful tool for the analysis and the purification of thiolated biomolecules. The methods developed are technically simple and robust and allowed the first full characterization of pure APM. Moreover, the efficacy of APM, as a biochemical tool, was demonstrated by analysis of tRNA thiolation by APM-PAGE.

Reversible fluorescent probe for highly selective and sensitive detection of mercapto biomolecules.

A coumarin-derived complex, Hg(2)L(2), was reported as a highly sensitive and selective probe for the detection of mercapto biomolecules in aqueous solution. The addition of Cys to a 99% aqueous solution of Hg(2)L(2) resulted in rapid and remarkable fluorescence OFF-ON (emission at 525 nm) due to the ligand-exchange reaction of Cys with L coordinated to Hg(2+). The increased fluorescence can be completely quenched by Hg(2+) and recovered again by the subsequent addition of Cys. Such a fluorescence OFF-ON circle can be repeated at least 10 times by the alterative addition of Cys and Hg(2+) to the solution of Hg(2)L(2), indicating that it can be used as a convertible and reversible probe for the detection of Cys. The interconversion of Hg(2)L(2) and L via the decomplexation/complexation by the modulation of Cys/Hg(2+) was definitely verified from their crystal structures. Other competitive amino acids without a thiol group cannot induce any fluorescence changes, implying that Hg(2)L(2) can selectively determine mercapto biomolecules. Using confocal fluorescence imaging, L/Hg(2)L(2) as a pair of reversible probes can be further applied to track and monitor the self-detoxification process of Hg(2+) ions in SYS5 cells.

Synthesis and application of organomercury haptens for enzyme-linked immunoassay of inorganic and organic mercury.

Two organomercury haptens were synthesized via the classical oxymercuration reaction. An intramolecular oxymercuration reaction was the strategy employed to prepare a structurally simple, but chemically robust, organomercury hapten that was conjugated to chicken immunoglobulin G (IgG). The resulting immunogen afforded mouse anti-mercury antibodies that were evaluated in an enzyme-linked immunosorbent assay (ELISA). Antibodies demonstrating high titers were obtained, and various immunoassay parameters were investigated. The sensitivity and selectivity of the resulting antibodies were evaluated by exploring different cross-coupling chemistries and solid-phase synthetic variations. A second hapten was prepared with the intermolecular oxymercuration reaction, and the resulting compound, once coupled to carrier protein, afforded a solid-phase conjugate that revealed the versatility of the mouse anti-mercury antibody. The anti-mercury antibody developed in this study was capable of detecting both mercury(II) salts and organomercury compounds.

Temperature-dependent supramolecular motif in coordination compounds.

The temperature-dependent structures of 1D and 2D HgCl(2) coordination polymers containing a N-(2-pyridylmethyl)-2-pyrazinecarboxamide flexible ligand with different motifs have been investigated. Results show that when the reaction was carried out at 60 degrees C, a 2D framework containing cubane-like units was generated, whereas in room temperature, L-bridged pentanuclear units, which are extended to a 1D band through a Hg-Cl-Hg-bridged compound, will be obtained.

Silaphenylmercuric triflate catalyzed reactions: synthesis of a solid-supported mercuric salt catalyst.

Let it flow, let it flow: A procedure to generate the first solid-supported mercuric salt, silaphenylmercuric triflate, is described. Silaphenylmercuric triflate showed remarkable catalytic activity for an indole synthesis, furanoyne cyclization, arylyne cyclization, and tandem carbocyclizations. An efficient flow reaction system for indole synthesis and arylyne cyclization is also described (see figure).

Diaza-18-crown-6 appended dual 7-hydroxyquinolines; mercury ion recognition in aqueous solution.

8,8'-(1,4,10,13-Tetraoxa-7,16-diazacyclooctadecane-7,16-diyl)bis(methylene)diquinolin-7-ol (TDBQ) was synthesized and proved to recognize Hg2+ via reducing Hg2+ to Hg+, forming a unique Hg(2)2+ - complex.

Ultraselective fluorescent sensing of Hg2+ through metal coordination-induced molecular aggregation.

A new type of fluorescent sensor has been developed from a perylene based molecule, N,N'-dideoxythymidine-3,4,9,10-perylene-tetracarboxylic diimide (TT-PTCDI); the strong, highly selective binding between the thymine ligand (T) and Hg2+ ion enables efficient sensing of mercury ions based on a fluorescence quenching mechanism, which is primarily caused by metal-coordination induced molecular aggregation.

Synthesis, characterization and antimicrobial activity of Fe(II), Zn(II), Cd(II) and Hg(II) complexes with 2,6-bis(benzimidazol-2-yl) pyridine ligand.

2,6-Bis(benzimidazol-2-yl)pyridine (L) ligand and complexes [M(L)Cl(2)] and [Fe(L)(2)](ClO(4))(2) (M=Zn, Cd, Hg) have been synthesized. The geometries of the [M(L)Cl(2)] complexes were derived from theoretical calculation in DGauss/DFT level (DZVP basis set) on CACHE. The central M(II) ion is penta-coordinated and surrounded by N(3)Cl(2) environment, adopting a distorted trigonal bipyramidal geometry. The ligand is tridentate, via three nitrogen atoms to metal centre and two chloride ions lie on each side of the distorted benzimidazole ring. In the [Fe(L)(2)](ClO(4))(2) complex, the central Fe(II) ion is surrounded by two (3N) units, adopting a octahedral geometry. The elemental analysis, molecular conductivity, FT-Raman, FT-IR (mid-, far-IR), (1)H, and (13)C NMR were reported. The antimicrobial activities of the free ligand, its hydrochloride salt, and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against 10 bacteria and the results compared with that for gentamycin. Antifungal activities were reported for Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, Hanseniaspora guilliermondii, and the results were referenced against nystatin, ketaconazole, and clotrimazole antifungal agents. In most cases, the compounds tested showed broad-spectrum (Gram positive and Gram negative bacteria) activities that were either more effective than or as potent as the references. The binding of two most biologically effective compounds of zinc and mercury to calf thymus DNA has also been investigated by absorption spectra.

(Nitrato-kappaO)bis(pyridine-2-carboxamide-kappa2N1,O)mercury(II) nitrate.

In the title compound, [Hg(NO3)(C6H6N2O)2]NO3, the Hg(II) atom is five-coordinate. The distorted square-pyramidal mercury(II) coordination environment is achieved by two N,O-bidentate picolinamide ligands, with one O-monodentate nitrate ion in the apical position. A seven-coordinate extended coordination environment is completed by two additional weak Hg...O interactions, one from the coordinated nitrate ion and one from the other nitrate ion, to give seven-coordination. The molecules are linked into a two-dimensional network by N-H...O hydrogen bonds.

Specific modification of Escherichia coli RNA polymerase with monomercury derivative of fluorescein acetate.

The method of specific modification of RNA polymerase with a monomercuric fluorescein derivative, fluorescein-monomercuriacetate (FMMA), is proposed. Under an appropriate condition of modification, FMMA is capable of mercaptid bonding with one of the alpha-subunits. It is shown that covalent modification with FMMA does not affect the kinetic parameters (KB and k2) of RNA synthesis nor does it lead to the inhibition of the overall RNA synthesis. The spectral characteristics of FMMA covalently bound to RNA polymerase were found to be sensitive to some temperature-induced conformational alterations of RNA polymerase, indicating that the labeled enzyme allows study of conformational behaviour of RNA polymerase during its functioning.

[The synthesis and fluorescence properties of doping europium-benzoic acid-phenanthroline complexes].

Eu1-x Lnx (BA)3Phen(Ln: Gd, La, Y; BA: benzoic acid; Phen: phenanthroline; x = 0.0-0.9) complexes are synthesized, and their similar structures showed by IR spectra. Fluorescence spectra indicate that the complexes can emit intense characteristic fluorescence from europium ion and the doping elements can enhance the fluorescence intensities of central europium ion and have co-fluorescence effect.

Hybromet: a ligand for purifying opioid receptors.

Condensation of the Grignard reagent derive from 2-[4-(allyloxy)phenyl]ethyl bromide (4b) with 7 alpha-acetyl-6,14-endo-ethenotetrahydrothebaine (5) furnished the (R) tertiary carbinol, 7, which upon methoxymercuration followed by treatment with the KBr gave the bromomercurio compound 10 (Hybromet). The corresponding N-cyclopropylmethyl analogue, 11, was prepared also. The bromomercurio compound, 1, and the mercaptobenzothiazole derivative, 3, gave allyl phenyl ether when treated with BAL at room temperature. Similar treatment of 10 with BAL gave 7 in high yield. Binding studies using rat brain homogenates indicated that 7, 13, and 14 have moderately high affinities for mu rather than delta binding sites. Although much weaker, 10 showed preferential mu binding also. These results along with the fact that 10 reacted smoothly with sulfhydryl groups suggest that Hybromet would be a suitable ligand for use in affinity chromatography.

Radiopharmaceuticals for acutely damaged myocardium. II: Synthesis and evaluation of [203Hg] hydroxymercurifluoresceins.

Six [203Hg] hydroxymercurifluoresceins were prepared by two methods and compared with [3H] fluorescein, [131I] rose bengal, and [203Hg] mercuric nitrate, in a rat model for myocardial necrosis, to determine their specificities for damaged myocardium (DM). The nonhalogenated [203Hg] hydroxymercurifluorescein had the highest ratios of the series for DM/normal heart (51.5+/-13.5) and DM/blood (22.1+/-8.1). Halide substituents at the 2' or 4' positions of the fluorescein moiety decreased the tissue selectivity, and bis-hydroxymercuration had no significant effect. The six tracers studied had greater absolute uptake and better target-to-nontarget ratios than [3H] fluorescein, [131I] rose bengal, or [203Hg] mercuric nitrate, indicating a cooperative effect between the fluorescein and hydroxymercuri-moieties in the overall sequestration process in damaged tissues.

Oxymercuration of homoallylic alcohol derived hemiacetals: diastereoselective synthesis of protected 1,3-diols.

[reaction: see text] Protected 1,3-diol synthons may be synthesized efficiently from homoallyic alcohols and simple aldehydes by oxymercuration of the derived hemiacetals. The reactions are diastereoselective and proceed without the use of solvent. Both Hg(OAc)2 and HgClOAc are effective in the reaction, and the latter produces isolable organomercurial chlorides directly.

Rhodium-catalyzed formylation of organomercurials: application to efficient polyol synthesis.

The rhodium-catalyzed formylation of organomercurials-a new transformation of organomercurials-is reported. The addition of 0.50 equiv of 1,4-diazabicyclo[2.2.2]octane (DABCO) was found to promote the reaction, and it is postulated that the DABCO acts as a ligand for mercury. Several examples are presented to document the scope of the reaction. This reaction was developed in the context of a larger program focused on the development of efficient strategies for the synthesis of polyol-derived natural products, and an efficient (8 steps) synthesis of Tolypothrix pentaether that employs this methodology is reported.

Organomercury(II) complexes of kojic acid and maltol: synthesis, characterization, and biological studies.

A number of organomercury(II) complexes of kojic acid (HL1, I) and maltol (HL2, II) of the type p-XC6H4HgL1 (III) and p-XC6H4HgL2 (IV) [X = Me, MeO, NO2] have been synthesized and characterized. [formula: see text] Conductance measurements indicate the nonelectrolyte behavior of the complexes. From IR and UV studies, the bonding modes of the ligands to the organomercury(II) moieties have been elucidated. The 1H and 13C NMR spectra support the stoichiometry of the complexes. The fragmentation pattern has been analyzed on the basis of mass spectra. From thermal studies (TG and DTA), various kinetic and thermodynamic parameters for thermal degradation have been enumerated. The complexes have been screened against some pathogenic bacterial strains. The bactericidal activity has been correlated with the thermal data.

Organomercury (II) complexes with anti-carcinogenic agents. I. Synthesis and characterization.

A few organomercury (II) complexes involving anti-carcinogenic ligands have been synthesized. The compounds are of the type p-MeOC6H4HgL1 (I), p-NO2C6H4HgL2 (II), p-MeOC4H4HgL3 (III) and p-MeC6H4HgL4 (IV) (HL1-6-mercaptopurine, HL2-6-thioguanine, HL3-5-fluorouracil, L4-phenyldithiocarbazate). Their composition has been determined from elemental analysis. Thin layer chromatography (TLC) studies demonstrate that the compounds are pure. Conductance measurement reveal that these derivatives are non-electrolytes. From IR and UV spectral studies the bonding modes of the ligands to the mercury (II) ion have been elucidated. The stoichiometry of the compounds has been confirmed on the basis of 1H and 13C NMR spectra. Some preliminary results of anti-neoplastic activity are reported.

N-containing Ag(I) and Hg(II) complexes: a new class of antibiotics.

Several classes of antimicrobial compounds are presently available; microorganism's resistance to these drugs constantly emerges. In order to prevent this serious medical problem, the elaboration of new types of antibacterial agents or the expansion of bioactivity of the naturally known biosensitive compounds is a very interesting research problem. The synthesis and characterization of metal complexes with organic bioactive ligands is one of the promising fields for the search. The biological activities of the metal complexes differ from those of either the ligand or the metal ion. The results obtained thus far have led to the conclusion that structural factors, which govern antimicrobial activities, are strongly dependent on the central metal ion. A review of papers dealing with the Ag(I) and Hg(II) complexes of N donor ligands is presented. These metal complexes of N-chelating ligands have attracted considerable attention because of their interesting physicochemical properties and pronounced biological activities. This review will mainly focus on the preparation procedures and antibacterial properties of free organic ligands and the corresponding complexes. Finally, a research about antimicrobial properties of new Hg(II) complexes with 5-methyl-5-(4-pyridyl)-2,4-imidazolidenedione (L) and various halogen ions, HgL2X2 (X = Cl¯ (49), Br¯ (50), and I¯ (51)), is reported. Noteworthy antimicrobial activities, evaluated by minimum inhibitory concentration, for these complexes were observed.

Reactions of a methylmercury zwitterionic thiolate complex [MeHg(Tab)]PF6 with various donor ligands: relevance to methylmercury detoxification.

Reaction of MeHgI with Ag(2)O in H(2)O followed by addition of equimolar TabHPF(6) in MeCN gave rise to a methylmercury zwitterionic thiolate complex [MeHg(Tab)]PF(6) (1) (TabH = 4-(trimethylammonio)benzenethiol) in a high yield. Treatment of 1 with KI and KSCN afforded an anion exchange product [MeHg(Tab)]I·0.25H(2)O (2·0.25H(2)O) and [MeHg(Tab)]SCN (3), respectively, while that of 1 with equimolar Tab resulted in the formation of another MeHg/Tab compound [MeHg(Tab)(2)]PF(6) (4). The cation of 2 or 3 shows an approximately linear structure in which the central Hg(II) is coordinated by one C atom of one CH(3) group and one S atom of a Tab ligand. The Hg(ii) center of the cation of 4 is trigonally coordinated by one C atom of the CH(3) group and two S atoms of two Tab ligands. The analogous reaction of 1 with NH(4)SCN led to the cleavage of the Hg-C bond of 1 and the formation of a known four-coordinated Hg(II)/Tab complex [Hg(Tab)(2)(SCN)(2)] (5). When 4 was treated with 4,6-Me(2)pymSH or EtSH, another four-coordinated Hg(II)/Tab complex [Hg(Tab)(4)](3)(PF(6))(6) (6) was generated in a high yield. The Hg(II) center of each cation of 6 is tetrahedrally coordinated by four S atoms of four Tab ligands. The results suggested that cleavage of the Hg-C bond in the methylmercury complex 1 could be completed by increasing the coordination number of its Hg(II) center by S-donor ligands and protonating the methyl group by weak acids.