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.

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.

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.

New terphenyl based mercury ensemble for detection of acetate ions in a plasma like system.

A new terphenyl based chemosensor 3 has been designed and synthesized. The binding behavior of 3 and its chemosensing ensemble 3-Hg toward various anions (F(-), Cl(-), Br(-), I(-), HSO(4)(-), H(2)PO(4)(-), CH(3)COO(-), NO(3)(-), N(3)(-), SO(4)(2-), SO(3)(2-), and Cr(2)O(7)(2-)) has been investigated by UV-Vis, fluorescence and NMR spectroscopy. Compound 3 shows a sensitivity for both F(-) and CH(3)COO(-) ions among various anions tested, whereas the ensemble 3-Hg shows a better selectivity for CH(3)COO(-) ions. The ensemble is utilized for CH(3)COO(-) recognition in a blood plasma like system.

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.

Bioinspired FeIIICdII and FeIIIHgII complexes: synthesis, characterization and promiscuous catalytic activity evaluation.

In this work we report on the synthesis, crystal structure, and physicochemical characterization of the novel dinuclear [Fe(III)Cd(II)(L)(µ-OAc)(2)]ClO(4)·0.5H(2)O (1) complex containing the unsymmetrical ligand H(2)L=2-bis[{(2-pyridyl-methyl)-aminomethyl}-6-{(2-hydroxy-benzyl)-(2-pyridyl-methyl)}-aminomethyl]-4-methylphenol. Also, with this ligand, the tetranuclear [Fe(2)(III)Hg(2)(II)(L)(2)(OH)(2)](ClO(4))(2)·2CH(3)OH (2) and [Fe(III)Hg(II)(L)(µ-CO(3))Fe(III)Hg(II)(L)](ClO(4))(2)·H(2)O (3) complexes were synthesized and fully characterized. It is demonstrated that the precursor [Fe(III)(2)Hg(II)(2)(L)(2)(OH)(2)](ClO(4))(2)·2CH(3)OH (2) can be converted to (3) by the fixation of atmospheric CO(2) since the crystal structure of the tetranuclear organometallic complex [Fe(III)Hg(II)(L)(µ-CO(3))Fe(III)Hg(II)(L)](ClO(4))(2)·H(2)O (3) with an unprecedented {Fe(III)(µ-O(phenoxo))(2)(µ-CO(3))Fe(III)} core was obtained through X-ray crystallography. In the reaction 2→3 a nucleophilic attack of a Fe(III)-bound hydroxo group on the CO(2) molecule is proposed. In addition, it is also demonstrated that complex (3) can regenerate complex (2) in aqueous/MeOH/NaOH solution. Magnetochemical studies reveal that the Fe(III) centers in 3 are antiferromagnetically coupled (J=-7.2cm(-1)) and that the Fe(III)-OR-Fe(III) angle has no noticeable influence in the exchange coupling. Phosphatase-like activity studies in the hydrolysis of the model substrate bis(2,4-dinitrophenyl) phosphate (2,4-bdnpp) by 1 and 2 show Michaelis-Menten behavior with 1 being ~2.5 times more active than 2. In combination with k(H)/k(D) isotope effects, the kinetic studies suggest a mechanism in which a terminal Fe(III)-bound hydroxide is the hydrolysis-initiating nucleophilic catalyst for 1 and 2. Based on the crystal structures of 1 and 3, it is assumed that the relatively long Fe(III···)Hg(II) distance could be responsible for the lower catalytic effectiveness of 2.

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.

Mercuric mercaptide of penicillenic acid, a novel hapten for relevant immunoassay, synthesized from penicillin.

The synthesis of mercuric mercaptide of penicillenic acid (MMPA) has been the basis for detection of penicillin for nearly 40 years (J. Pharm. Pharmacol., 1972, 24, 790; Chinese Pharmacopoeia Ed. II, 1995). Herein, experiments were performed on: (1) synthesis of MMPA used as a novel mercuric hapten, (2) preparation of mercuric antigen of MMPA-BSA, (3) production of antibodies by rabbits immunized with the antigen, and (4) properties of the antibodies studied by ELISA. The results show that: (1) the antigen is safe for immunized animals; (2) high titer antibodies against MMPA are obtained implying good immunogenicity of the antigen; (3) antisera show slightly higher affinity to OVA-GHS-HgCl than OVA-GSH, indicating weak specific affinity of antisera against mercuric ion. Even the weak specific affinity, the hapten and its antigen have potential uses in immunoassays of mercuric ion in environment and food samples, because of easy chemical selective conversion from mercuric ion to MMPA and complete decomposition of un-reacted penicillin in acidic solution.

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.

Preparation and comprehensive characterization of [Hg6(alanine)4(NO3)4].H2O.

A new mercury-alanine complex has been isolated from reaction mixtures of mercurous nitrate dihydrate and alanine (L and D enantiomers). The solid-state structure contains mercury(I) and mercury(II) associated by alanine ligands in a polymeric array. The disproportionation of mercury(I) to mercury(II) and mercury(0) was facilitated by alanine and is evidenced by the appearance of mercury(0) in reactions of mercury(I) with the 20 common amino acids. This complex is the first mercury(I)-amino acid complex characterized in the solid state. The compounds have been comprehensively characterized using X-ray crystallography, solid-state and solution-state nuclear magnetic resonance spectroscopy, vibrational spectroscopies, and electrospray ionization mass spectrometry.

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.

Binding of HgCl2 by tripodal ligands controlled by AgPF6: receptors for the PF6- anion.

Mercuric chloride can readily enter into the biological cycle where it gets converted into other forms of mercury and causes severe neurotoxic, genotoxic and immunotoxic effects; a number of tripodal ligands have been synthesized that selectively bind mercuric chloride and in the presence of AgPF6, mercury can be removed and supramolecular complexes of the PF6- anion are formed.

(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.

Rhenium diazenide ternary complexes with dithiocarbamate ligands: towards new rhenium radiopharmaceuticals.

The reaction of the mono-diazenide core, [ReCl2(NNC6H(4)-4-OCH3)(NCCH3)(PPh3)2], with four equivalents of the sodium or potassium salts of dithiocarbamate (dtc) ligands gives neutral complexes of the formula [Re(NNC6H(4)-4-OCH3)(dtc)2(PPh3)]. It is possible to use a wide range of dithiocarbamate ligands (S2CNRR') with a variety of R groups (R=R'=methyl, phenyl or ethyl; R=methyl, R'=phenyl and R=R'=morpholino). Substitution reactions with dtc ligands on the mono-diazenide derived from 2-hydrazinopyridine, [ReCl2(NNC5H4N)(PPh3)2, give the analogous complexes, [Re(NNC6H5N)(dtc)2(PPh3)]. The new complexes have been characterised by a combination of NMR spectroscopy, mass spectrometry and X-ray crystallography. Cyclic voltammetry measurements in dimethyl formamide show that the rhenium diazenido-dtc complexes undergo a quasi-reversible oxidation tentatively assigned to a ReIII/ReIV oxidation. Since the parent complex, [ReCl2(NNC6H(4)-4-R)(NCCH3)(PPh3)2] can be prepared directly from perrhenate and readily derivatised with dtc ligands these complexes have potential relevance to the development of new therapeutic rhenium radiopharmaceuticals.

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.

Mercury(II) 2-aminoethanethiolate clusters: intramolecular transformations and mechanisms.

The combination of HgF2 and 2-aminoethanethiol (AET, with some AET.HCl present) yielded a cyclic tetranuclear thiolate, [Hg4Cl4(SCH2CH2NH2)4] (1), with alternating Hg and S atoms. The Cl from the reaction mixture led to the formation of Hg-Cl bonds with no Hg-F in the final product. In contrast, a similar reaction with HgBr2 yielded a nonanuclear cluster, [Hg9Br15(SCH2CH2NH3)15]3+ (2), and the disulfide salt {[HgBr4][(NH3CH2CH2S-)2]} (3). Despite similar reactions, the AET groups in 2 are protonated compared to the nonprotonated amine groups in 1, which allows the ligand to chelate the Hg atom in the latter compound. The reaction with HgI2 yielded a cyclic tetranuclear compound, [Hg4I6(SCH2CH2NH2)2(SCH2CH2NH3)2](H2O/EtOH) (4), containing protonated and nonprotonated AET groups. Compound 4 at room temperature irreversibly rearranges to [Hg4I4(SCH2CH2NH2)4] (5), which is isostructural to 1. A systematic pathway for the formation of 1 along with the intramolecular conversion of 4 to 5 is proposed. These compounds demonstrate that very diverse Hg-S compounds form under similar reaction conditions.

[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.