New mononuclear mercury(II) complexes of a bifunctionalized ylide containing five-membered chelate ring: Spectral and structural characterization

The reaction of a new bifunctionalized ylide, Ph₂PCH₂PPh₂C(H)C(O)(C₆H₄Cl) (2) with mercury(II) halides in equimolar ratios using dry methanol as solvent yielded the P, C-chelated complexes, {HgX₂[Ph₂PCH₂PPh₂C(H)C(O)(C₆H₄Cl)]} where X = Cl (3), Br (4), I (5). The structures of complexes 4 and 5 have been characterized crystallographically. Single crystal X-ray analyses reveal the presence of mononuclear complexes containing Hg atom in a distorted tetrahedral environment. Characterization of the obtained compounds was also performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. A theoretical study at DFT (B3LYP) level using standard CEP-31G basis set showed that the experimentally determined structure of the complex 5 is about 0.6-15.75 kcal mol⁻¹ more stable than its other bonding modes.     

Stereochemically non-rigid helical mercury(II) complexes

Reactions of the 1:2 condensate (L) of benzil dihydrazone and 2-acetylpyridine with Hg(ClO₄)₂ · xH₂O and HgI₂ yield yellow [HgL₂](ClO₄)₂ (1) and HgLI₂ (2), respectively. Homoleptic 1 is a 8-coordinate double helical complex with a Hg(II)N₈ core crystallising in the space group Pbca with cell dimensions: a = 16.2250(3), b = 20.9563(7), c = 31.9886(11) Å. Complex 2 is a 4-coordinate single helical complex having a Hg(II)N₂I₂ core crystallising in the space group P2₁/n with cell dimensions a = 9.8011(3), b = 17.6736(6), c = 16.7123(6) Å and β = 95.760(3)^o. In complex 1, the N-donor ligand L uses all of its binding sites to act as tetradentate. On the other hand, it acts as a bidentate N-donor ligand in 2 giving rise to a dangling part. From variable temperature ¹H NMR studies both the complexes are found to be stereochemically non-rigid in solution. In the case of 2, the solution process involves wrapping up of the dangling part of L around the metal.     

Zinc(II), cadmium(II) and mercury(II) complexes of the vitamin B1 antagonist oxythiamine

The reaction of oxythiamine chloride hydrochloride (HOxTCl x HCl) with ZnCl2, CdCl2 and HgCl2 in ethanol yielded the complexes [ZnCl3(HOxT)], [CdCl3(HOxT)] and [HgCl3(HOxT)]. In water, the reaction with CdCl2 afforded [CdCl2(OxT)], but reaction with ZnCl2 or HgCl2 yielded unidentified products. The four new complexes were characterized by mass spectrometry and IR spectroscopy in the solid state and by 1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopy in hexadeuterated dimethylsulfoxide (DMSO-d6), and three were also studied by X-ray diffractometry. In [ZnCl3(HOxT)] and [HgCl3(HOxT)] the oxythiamine ligand is bound to the metal via N(1') and adopts the V conformation exhibited by thiamine in biological contexts. The infrared (IR) spectrum of [CdCl3(HOxT)] suggests a similar coordination mode. In [CdCl2(OxT)] each OxT zwitterion coordinates to one Cd(II) ion via its N(1') atom and to another via its N(3') and O atoms, giving rise to a polymeric chain along the x-axis. The coordination number of the metal is made up to six by Cdc...Cl interactions, two of which link the polymeric chains in pairs. This seems to be the first metal complex containing the oxythiamine ligand as a zwitterion, with the N(3')-H/O(4'alpha)-H group deprotonated. Neither HOxTCl nor its zinc(II) complex showed any significant activity in vitro against HeLa cells.     

Interferon induction by platinum(II)-poly(I).poly(C) complexes

The effect of the interaction between poly(I).poly(C) and cis-dichloro-diammineplatinum(II) (cis-Pt), its trans analogue and chloro-diethylene-triamminoplatinum(II) (dien-Pt) on interferon induction activity was investigated. The covalent monodentate fixation of the three compounds on N7 of inosine has different effects on the structure and thermostability of poly(I). poly(C) which is well reflected by the interferon induction activity of the samples. Thus, the sandwich stabilization by dien-Pt at low binding ratios is manifested by an increased interferon induction and a high resistance towards RNAase degradation. The destabilization of the duplex by cis-Pt decreases interferon induction, accompanied by an increase in RNAase sensitivity of the complexes. In the case of trans-Pt the duplex structure is little perturbed and interferon induction is essentially maintained.     

Biotoxicity of mercury as influenced by mercury(II) speciation

Integration of physicochemical procedures for studying mercury(II) speciation with microbiological procedures for studying the effects of mercury on bacterial growth allows evaluation of ionic factors (e.g., pH and ligand species and concentration) which affect biotoxicity. A Pseudomonas fluorescens strain capable of methylating inorganic Hg(II) was isolated from sediment samples collected at Buffalo Pound Lake in Saskatchewan, Canada. The effect of pH and ligand species on the toxic response (i.e., 50% inhibitory concentration [IC50]) of the P. fluorescens isolated to mercury were determined and related to the aqueous speciation of Hg(II). It was determined that the toxicities of different mercury salts were influenced by the nature of the co-ion. At a given pH level, mercuric acetate and mercuric nitrate yielded essentially the same IC50s; mercuric chloride, on the other hand, always produced lower IC50s. For each Hg salt, toxicity was greatest at pH 6.0 and decreased significantly (P = 0.05) at pH 7.0. Increasing the pH to 8.0 had no effect on the toxicity of mercuric acetate or mercuric nitrate but significantly (P = 0.05) reduced the toxicity of mercuric chloride. The aqueous speciation of Hg(II) in the synthetic growth medium M-IIY (a minimal salts medium amended to contain 0.1% yeast extract and 0.1% glycerol) was calculated by using the computer program GEOCHEM-PC with a modified data base. Results of the speciation calculations indicated that complexes of Hg(II) with histidine [Hg(H-HIS)HIS+ and Hg(H-HIS)2(2+)], chloride (HgCl+, HgCl2(0), HgClOH0, and HgCl3-), phosphate (HgHPO4(0), ammonia (HgNH3(2+), glycine [Hg(GLY)+], alanine [Hg(ALA)+], and hydroxyl ion (HgOH+) were the Hg species primarily responsible for toxicity in the M-IIY medium. The toxicity of mercuric nitrate at pH 8.0 was unaffected by the addition of citrate, enhanced by the addition of chloride, and reduced by the addition of cysteine. In the chloride-amended system, HgCl+, HgCl2(0), and HgClOH0 were the species primarily responsible for observed increases in toxicity. In the cysteine-amended system, formation of Hg(CYS)2(2-) was responsible for detoxification effects that were observed. The formation of Hg-citrate complexes was insignificant and had no effect on Hg toxicity.     

Interferon induction by platinum(II)-poly(I)·poly(C) complexes

The effect of the interaction between poly(I)·poly(C) and cis-dichloro-diammineplatinum(II) (cis-Pt), its trans analogue and chloro-diethylene-triamminoplatinum(II) (dien-Pt) on interferon induction activity was investigated. The covalent monodentate fixation of the three compounds on N⁷ of inosine has different effects on the structure and thermostability of poly(I)·poly(C) which is well reflected by the interferon induction activity of the samples. Thus, the sandwich stabilization by dien-Pt at low binding ratios is manifested by an increased interferon induction and a high resistance towards RNAase degradation. The destabilization of the duplex by cis-Pt decreases interferon induction, accompanied by an increase in RNAase sensitivity of the complexes. In the case of trans-Pt the duplex structure is little perturbed and interferon induction is essentially maintained.     

Synthesis and structural characterization of mercury(II) complexes with a novel ferrocenyliminophosphine

Synthesis of the novel ligand ferrocenyliminophosphine [(η⁵-C₅H₅)Fe{(η⁵-C₅H₄)CHN(C₆H₄-2-PPh₂)}] (1, L) and studies on its complexation properties with mercury (II) are reported. Halogen-bridged binuclear mercury (II) complexes [HgX(μ-X)L]₂ (X = Cl (2a), Br (2b)) and a mononuclear mercury (II) complex HgCl₂L₂ (4a) have been obtained under different reaction conditions. In both cases, the ferrocenyliminophosphine acts as a P-monodentate ligand and the imino nitrogen does not participate in coordination to mercury (II). All the new compounds 1, 2a, 2b and 4a were characterized by elemental analysis, ¹H NMR, ³¹P NMR and IR spectra. In addition, structures of 2a and 4a have been determined by X-ray single-crystal analysis.     

Biotoxicity of mercury as influenced by mercury(II) speciation.

Integration of physicochemical procedures for studying mercury(II) speciation with microbiological procedures for studying the effects of mercury on bacterial growth allows evaluation of ionic factors (e.g., pH and ligand species and concentration) which affect biotoxicity. A Pseudomonas fluorescens strain capable of methylating inorganic Hg(II) was isolated from sediment samples collected at Buffalo Pound Lake in Saskatchewan, Canada. The effect of pH and ligand species on the toxic response (i.e., 50% inhibitory concentration [IC50]) of the P. fluorescens isolated to mercury were determined and related to the aqueous speciation of Hg(II). It was determined that the toxicities of different mercury salts were influenced by the nature of the co-ion. At a given pH level, mercuric acetate and mercuric nitrate yielded essentially the same IC50s; mercuric chloride, on the other hand, always produced lower IC50s. For each Hg salt, toxicity was greatest at pH 6.0 and decreased significantly (P = 0.05) at pH 7.0. Increasing the pH to 8.0 had no effect on the toxicity of mercuric acetate or mercuric nitrate but significantly (P = 0.05) reduced the toxicity of mercuric chloride. The aqueous speciation of Hg(II) in the synthetic growth medium M-IIY (a minimal salts medium amended to contain 0.1% yeast extract and 0.1% glycerol) was calculated by using the computer program GEOCHEM-PC with a modified data base. Results of the speciation calculations indicated that complexes of Hg(II) with histidine [Hg(H-HIS)HIS+ and Hg(H-HIS)2(2+)], chloride (HgCl+, HgCl2(0), HgClOH0, and HgCl3-), phosphate (HgHPO4(0), ammonia (HgNH3(2+), glycine [Hg(GLY)+], alanine [Hg(ALA)+], and hydroxyl ion (HgOH+) were the Hg species primarily responsible for toxicity in the M-IIY medium. The toxicity of mercuric nitrate at pH 8.0 was unaffected by the addition of citrate, enhanced by the addition of chloride, and reduced by the addition of cysteine. In the chloride-amended system, HgCl+, HgCl2(0), and HgClOH0 were the species primarily responsible for observed increases in toxicity. In the cysteine-amended system, formation of Hg(CYS)2(2-) was responsible for detoxification effects that were observed. The formation of Hg-citrate complexes was insignificant and had no effect on Hg toxicity.     

Speciation of ternary complexes of lead(II), cadmium(II) and mercury(II) with L-dopa and phenanthroline in propanediol-water mixtures

Abstract

The formation constants of ternary complexes of title systems have been determined pH-metrically in biologically relevant conditions at an ionic strength of 0.16 mol dm^-3 and 303 K. The overall stability constants have been evaluated using MINIQUAD75 computer program. The complexation equilibria have been derived on the basis of species distribution diagram. In the present study L-Dopa and 1, 10-phenanthroline are found to be compatible ligands, proving greater stability of ternary complexes as compared to binary ones. The trend in variation of stability constants with change in dielectric constant of medium is explained on the basis of electrostatic and non-electrostatic forces. Distributions of the species with pH at different compositions of propanediol-water mixtures are also presented. The factors responsible for the compatibility of both the ligands have also been discussed.     

Immobilized chymotrypsin by means of Schiff base copper(II) chelate

A new method for cross-linking of protein was proposed in our previous work. The method is based on the spontaneous chelate formation process involving three components, salicylaldehyde moiety, alpha-amino acid residue and copper(II). In this paper versatility of the method as a purpose of immobilization of enzyme was described. Chymotrypsin-salicylaldehyde conjugate was immobilized to the agarose gel attached alpha-amino acid residue in the presence of copper(II) ion The enzyme was not eluted from the gel by washing with a copper free buffer though it was exclusively eluted by a medium containing EDTA. Catalytic activity of the chymotrypsin salicylaldehyde conjugate was not changed upon the immobilization. The method was proposed as a new tool for reversible immobilization of enzyme.     

Platinum(II) complexes with diaminopropionic acid as oxygen-bound unidentate,nitrogen—oxygen and nitrogen—2nitrogen chelate complexes

Reaction of diaminopropionic acid (Dap) monohydrochloride with K₂PtCl₄ in water gives two isomeric PtCl₂(O-Dap·HCl)₂ complexes co-ordinated through oxygen only which can be isolated in solid form; both isomers are converted upon short heating to PtCl₂(N,O-Dap), whereas prolonged heating yields PtCl₂(N,N-Dap).     

Silver(I), mercury(II) and palladium(II) complexes of functionalized N-heterocyclic carbenes: Synthesis, structural studies and catalytic activity

A series of NHC silver(I), mercury(II) and palladium(II) complexes, [(1,3-diethylbimy)₆Ag₄I₃]I (2), [(1-benzyl-3-picolylbimy)Ag₂Br₂]_n (3), [(1-benzyl-3-picolylbimy)HgI(CH₂CN)]₂ (4), {[(1-picolyl-3-npropylbimy)₂Hg][Hg₂I₆]}_n (5) and [(1,3-dipicolylbimy)PdCl]Cl (6), as well as one anionic complex [1,3-diethylbimidazolium]₂[HgI₄] (1) (bimy = benzimidazol-2-ylidene), have been prepared and characterized. Interestingly, a wind wheel-like Ag₄I₃ arrangement in 2 is formed, 1D polymeric chain containing 12-membered macrometallocycles and quadrangle Ag₂Br₂ units in 3 is generated, and the α-carbon atom of deprotonated acetonitrile ([CH₂CN]⁻) in 4 participates in coordination with mercury(II) atom. In the crystal packings of complexes 1-6, 2D supramolecular layers or 3D supramolecular architectures are formed via intermolecular weak interactions, including π-π interactions, hydrogen bonds, C-H···π contacts, weak Hg···I bonds and I···I bonds. Additionally, the catalytic activity of the NHC palladium(II) complex 6 in Suzuki-Miyaura cross-coupling reaction was studied.     

Chiral bimetallic complexes from chiral salen metal complexes and mercury (II) halides and acetates: the anionic groups interact with Cu(II) in apical position

A series of chiral bimetallic complexes have been prepared containing both Cu(II) and Hg(II) metal centers. The complexes possess chiral salen ligands which host Cu(II) in the center of the cis-N₂O₂ chromophore and Hg(II) via two oxygen atoms of the chromophore. Halogen and acetate groups from mercury salts interact with the Cu(II) center. The X-ray crystallographic data of 11 reveals a short distance of Cl?Cu (3.22-3.26 Å). EPR study also discloses a strong interaction, in particular, of acetate group with Cu.     

Bridged dinucleating N-heterocyclic carbene ligands and their double helical mercury(II) complexes

A series of six 3,6-bis(imidazolium-3-yl)pyridazine derivatives with different imidazole-N substituents have been synthesized and isolated as the salts [H₂L]Cl₂ (1a)-(6a) and [H₂L](PF₆)₂ (1b)-(6b). Solid state structures have been determined crystallographically for eleven out of the twelve compounds, revealing diverse hydrogen bonding patterns that involve the imidazolium-C²H units and the anions. N-heterocyclic carbene (NHC) mercury(II) complexes [Hg₂L₂](PF₆)₄ (7)-(9) are readily formed in good yields from ligand precursors [H₂L](PF₆)₂ and Hg(OAc)₂, as long as imidazole-N substituents are not too bulky. X-ray crystallography reveals double helical bimetallic arrangements for the stable [Hg₂L₂]⁴⁺ cations. Ligand scrambling in [Hg₂L₂]⁴⁺ occurs only in the presence of free carbene precursor, presumably via an associative mechanism.     

Semi-synthetic antibiotics: Titanium(IV), zirconium(IV) and mercury(II) complexes of 6-amino penicillinic acid

A number of organometallic derivatives involving 6-amino penicillinic acid (I), of the types η⁵-R)₂M- (Cl)L^?Et₃NH⁺ (II), (η⁵-R)₂M(Cl)L (III) and R′HgL [R = cyclopentadienyl (C₅H₅), indenyl (C₉H₇), R′ = phenyl (C₆H₅), p-acetoxyphenyl (p-CH₃COOC₆H₄), o-hydroxyphenyl (o-HOC₆H₄), p-hydroxyphenyl (p-HOC₆H₄); M = Ti(IV), Zr(IV); LH = 6-amino penicillinic acid] have been synthesized and characterized. Conductance measurements indicate that while the (η⁵-R)₂M(Cl)L^?Et₃NH⁺ complexes are 1:1 electrolytes, the remaining compounds are non-electrolytes. From IR and UV spectral studies it is concluded that the penicillin moiety is bidentate. PMR and CMR studies support the stoichiometry of the complexes. Fluorescence studies have been carried out for o- and p-HOC₆H₄HgL complexes and relevant photochemical parameters have been elucidated. X-ray diffraction studies have been made for the o-HOC₆H₄HgL complex. For the C₆H₅HgL, p-CH₃COOC₆H₄HgL and p-HOC₆H₄HgL complexes, thermal studies (TG and DTA) have been carried out and kinetic parameters for thermal degradation have been enumerated. In addition, the fragmentation pattern of these complexes has been analysed on the basis of mass spectra. The C₆H₅HgL and p-CH₃COOC₆H₄HgL complexes show positive bactericidal activities.     

Inhibition by diphenols of the induction of micronuclei by gamma-radiation

A study was made of the influence of diphenols (for instance, resorcinol, hydroquinone, and pyrocatechin) on gamma-radiation induction of micronuclei (1.5 Gy). The position of the diphenol molecule hydroxyl group (the isomeric effect) was shown to influence their antimutagenic activity. This antimutagenic effect of the diphenols is associated with their ability to produce semiquinone and quinone forms which are peculiar for the process of oxidation of pyrocatechin (ortho-) and hydroquinone (para-) as opposed to resorcinol (meta-position of the hydroxyl group).     

Prophage induction and mutagenicity of a series of anti-tumour platinum(II) and platinum(IV) co-ordination complexes

11 platinum compounds with nitrogen donor ligands, previously tested for anti-tumour activity, were studied for induction of prophage lambda and for mutagenicity in the Ames assay, with various strains of Salmonella. The compounds included cis and trans isomers of Pt(II) and Pt(IV) complexes and were tested with and without metabolic activation. All the cis compounds elicited prophage induction, whereas the trans compounds were inactive. Mutagenicity was found only in strains containing the R factor, indicating that SOS-type repair processes are required for the conversion of initial DNA lesions into mutations. Mutation induction was also influenced by the excision-repair process. The 2 trans compounds were not, or only slightly, mutagenic; all other compounds were mutagenic in at least one strain, exhibiting a 2-20-fold increase over the spontaneous background level. Addition of liver homogenate had no significant effect on the number of mutants. One compound induced exclusively frameshift mutations. The other mutagenic compounds induced frameshift mutations as well as base-pair substitutions. 7 compounds were more mutagenic for the repair-proficient than for the repair-deficient strains; only one showed the opposite effect. This suggests that for mutagenicity testing of platinum compounds, repair-proficient strains are more sensitive indicators. The differences in response of the various strains are more sensitive indicators. The differences in response of the various strains toward the compounds suggest the formation of different DNA lesions and/or a selective action of repair processes on these lesions. In general, a good qualitative correlation was observed between prophage-inducing capacity, mutagenicity in bacterial and mammalian cells and anti-tumour activity.     

Synthesis, characterization, and structural studies of mercury(II) complexes of new bidentate phosphorus ylide

The reaction of Ph₂PCH₂CH₂PPh₂ (dppe) with BrCH₂C(O)C₆H₄NO₂ (1:1.05 molar ratio) in acetone produces a mixture of the new monophosphonium salt [Ph₂PCH₂CH₂PPh₂CH₂C(O)C₆H₄NO₂]Br (1) and the diphosphonium salt [NO₂C₆H₄C(O)CH₂PPh₂CH₂CH₂PPh₂CH₂C(O)C₆H₄NO₂]Br₂ (2). Compound 2 was insoluble in acetone and thus easily separated from the solution of 1. Further, by reacting both the mono- and diphosphonium salts with the appropriate bases the bidentate phosphorus ylides, [Ph₂PCH₂CH₂PPh₂CHC(O)C₆H₄NO₂] (3) and [NO₂C₆H₄C(O)CHPPh₂CH₂CH₂PPh₂CHC(O)C₆H₄NO₂] (4) were obtained. The reaction of ligand 3 with mercury(II) halides in dry methanol leads to the formation of the P,P-coordinated monomeric complexes {HgX₂(Ph₂PCH₂CH₂PPh₂CHC(O)C₆H₄NO₂)₂} [X = Cl (5), Br (6), I (7)]. The structure of complex 7 being unequivocally determined by single crystal X-ray diffraction techniques. Characterization of these species was also performed by elemental analysis, IR spectroscopy and ¹H, ³¹P, and ¹³C NMR techniques. These analyses being consistent with a 2:1 stoichiometry ylide/Hg(II) for compounds 5 through 7. Results obtained from theoretical studies are also consistent with a product in which two ylides are coordinated to the Hg(II) center through their phosphine groups, being this product the most stable among all the possible products.     

重金属汞螯合物人工抗原的合成与鉴定

以异硫氰酸苄基乙二胺四乙酸为双功能螯合剂,合成了半抗原,并将半抗原与钥孔戚血蓝素或牛血清白蛋白偶联制备抗原。用二喹啉甲酸(BCA)法测抗原浓度,对半抗原、抗原、KLH和BSA分别进行紫外分光光度计扫描, 利用SDS-PAGE电泳进行定性鉴定,用三硝基苯磺酸法间接测偶联率,用石墨炉原子分光吸收法检测抗原中Hg2+的含量。研究结果表明抗原合成成功, Hg-ITCBE-KLH、Hg-ITCBE-BSA、ITCBE-BSA中载体蛋白ε-氨基的替换程度依次为34.75±4.60％、40.61±0.99％、61.27±0.69％, Hg2+的含量依次为分：38.4±0.5μg/ml、125.5±0.9μg/ml、0μg/ml。