Factors influencing changes in mercury concentrations in lake water and yellow perch (<Emphasis Type="Italic">Perca flavescens</Emphasis>) in Adirondack lakes

Over the past 20+ years, fish with elevated concentrations of mercury (Hg) have been observed in remote lake districts, including the Adirondack region of New York. Across eastern North America studies have also reported a negative correlation between fish Hg concentration and lake pH. Recent controls in emissions of sulfur dioxide (SO₂) have resulted in some improvement in the acid–base status of acid-impacted surface waters including Adirondack lakes. In addition, there has been an apparent decrease in atmospheric Hg deposition. A synoptic survey of 25 lakes in the Adirondacks was conducted in 1992–1993 to analyze spatial patterns of Hg in the water column and yellow perch (Perca flavescens). The same cluster of 25 lakes was resurveyed in 2005–2006 to evaluate if changes in lake concentrations of Hg species or fish Hg have occurred. We observed a varied response of changes in water chemistry and fish Hg concentrations. In twelve of the resurveyed lakes the yellow perch had lower Hg concentrations, six lakes had yellow perch with higher Hg concentrations, and in seven lakes yellow perch Hg concentrations did not change significantly (α = 0.05). Four variables appear to influence the change in yellow perch Hg concentrations in the Adirondacks: watershed area, elevation, change in pH, and change in fish body condition. We hypothesize that as the acidity in lakes is attenuated, the lakes may become more productive and/or water quality conditions less stressful to fish leading to increasing fish body condition. As fish body condition improves, fish exhibit “growth dilution” of tissue contaminants leading to lower fish Hg concentrations.     

Formation of the nanostructure on a silica surface as mercury(II) ions adsorption sites

The present work investigates the adsorptive interactions of Hg(II) ions with hydroxylated silica, aminopropylsilica and silica chemically modified by β-cyclodextrin in aqueous medium. Batch adsorption studies were carried out with various agitation time and mercury(II) concentration. The maximum adsorption was observed within 15-30 min of agitation. The kinetics of the interactions, tested with model of Lagergren for pseudo-first and pseudo-second order equations, showed better agreement with first order kinetics (k₁ = 3.4 ± 0.2 to 5.9 ± 0.3 min⁻¹). The adsorption data gave good fits with Langmuir isotherms. The results have shown that β-cyclodextrin-containing adsorbent has the largest adsorption specificity to Hg(II) : K_L = 14 400 ± 700 L/mg. “β-Cyclodextrin-” inclusion complexes with ratio 1:1 and super molecules with composition С₄₂H₇₀O₃₅ · 3Hg(NO₃)₂ are formed on the surface of β-cyclodextrin-containing silica.     

Syntheses, structures, thermal behavior and solution studies of two types of Hg(II) complexes with [1,3-di(2-methoxy)benzene]triazene

The reaction of [1,3-di(2-methoxy)benzene]triazene, [HL], with Hg(CH₃COO)₂ and Hg(SCN)₂ in methanol as solvent, resulted in the formation of [HgL₂] (1) and [HgL(SCN)] (2), respectively. These compounds were characterized by means of X-ray diffraction, FT-IR spectroscopy, CHN and TGA-DTA analysis. In the lattice of the compound 1, the mono-nuclear complexes were connected to dimer structure by intermolecular non-classical C-H···O hydrogen bonds. Also, weak Hg-η²-arene π-interactions link the dimers into 1D supramolecular chains. The compound 2 is a 2D coordination polymer induced by C-H···π stacking interactions between 1D chains produced by weak Hg-η³-η³-arene π-interactions. The results of studies of the stoichiometry and formation of complexes of 1 and 2 in methanol solution were found to be in support of their solid state stoichiometry.     

Synthesis and structures of polymeric silver and mercury complexes with amido-functionalized N-heterocyclic carbenes

Four amido-functionalized N-heterocyclic silver(I) and mercury(II) carbene complexes, [(CH₃-imy-CH₂CONH₂)₂Ag₂Br₂] (3), [Ag(CH₃-bimy-CH₂CONH₂)₂]₄[Ag₄Br₈] (4), [Hg(CH₃-imy-CH₂CONH₂)₂][HgBr₄] (5), and [Hg(CH₃-bimy-CH₂CONH₂)₂][HgBr₄] (6), have been synthesized and structurally characterized. Crystal packing revealed a 2D polymeric structure of complex 3. In addition to a repeated interaction between the Ag₂Br₂ units responsible for the 1D polymeric ladder structure, a pair of hydrogen bonding interactions between the amido groups of the adjacent molecules provided a basis for the other dimension of the polymeric chain. Complex 4 is comprised of a unique oligomeric anion [Ag₄Br₈]⁴⁻ and four [Ag(CH₃-bimy-CH₂CONH₂)₂]⁺ cations. Crystal packing of 4 revealed a one-dimensional polymeric structure in which the cations are connected to each other through a pair of hydrogen bonding interactions between the adjacent amido groups. Compounds 5 and 6 are both ionic consisting of a mercury carbene cation and [HgBr₄]²⁻ anion. An intramolecular interaction of the amido oxygen with the mercury atom of the cation was observed in these two complexes. The interaction between the mercury of the cation and a bromide of the anion, along with the hydrogen bonding interaction of the adjacent amido groups, is responsible for the 2D polymeric structures of these two complexes in the solid state.     

Mercury(II) acetate/thiocyanate coordination polymers with n-donor ligands, spectroscopic, thermal and structural studies

Three new mercury(II) coordination polymers, [Hg₂(μ-bpa)(μ-SCN)₂(μ-CH₃COO)₂]_n (1), [Hg₂(μ-4-bpdb)_1.5(μ-CH₃COO)(μ_1,1- SCN)(μ_1,3-SCN)(SCN)]_n · CH₃CN (2) and [Hg(μ-3-bpdb)(CH₃COO)₂]_n (3) {(bpa = 1,2-bis(4-pyridyl)ethane, 4-bpdb) = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, have been synthesized and characterized by CHN elemental analysis and IR spectroscopy. The single crystal X-ray data show the compound 1 is two-dimensional coordination polymer as a result of simultaneously bridging 1,2-bis(4-pyridyl)ethane, acetate and thiocyanate ligands. The single-crystal X-ray data of the compound 2 show that the complex to be a two-dimensional polymer, one of Hg atoms has four-coordinate and one of them has seven-coordinate. Three SCN⁻ anions show three different coordination modes with terminal, μ_1,1-bridge and μ_1,3-bridge fashions. The structural studies of compound 3 show the structure may be considered a one-dimensional coordination polymer of mercury(II) consisting of linear chains formed by a bridging 3-bpdb ligand. The thermal stabilities of these compounds were studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

Synthesis and characterization of binuclear mercury(II) complexes of phosphorus ylides, X-ray analysis and multinuclear NMR measurements

The reactions of phosphorus ylide (p-tolyl)₃PCHC(O)CH₃ (Y₁) with HgX₂ (X = Cl and Br) and (p-tolyl)₃PCHC(O)C₆H₄NO₂ (Y₂) with HgX₂ (X = Cl, Br and I) in equimolar ratios using methanol as a solvent are reported. These reactions led to binuclear complexes. C-Coordination of ylides and trans-like structure of complexes [(Y₁) · HgBr₂]₂ and [(Y₂) · HgBr₂]₂ · 2DMSO are demonstrated by single crystal X-ray analyses. The IR, ¹H, ¹³C and ³¹P NMR data for the other synthesized compounds are similar to the latter complexes, indicating similar structures. Elemental analyses indicate a 1:1 stoichiometry between the ylide and Hg(II) halide in all the products. The ab initio studies indicated that for all dimeric compounds, the observed trans-like structures are 7-10 kcal/mol more stable than the alternative possible cis-like isomers. Although the calculated bond lengths are slightly longer than the measured ones, the similarity of calculated and measured bond angles reflects the similar geometrical structures for these compounds in both the solid state and the gas phase.     

A selective phosphorescent chemodosimeter for mercury ion

The synthesis and crystal structure of an anionic phosphorescent iridium complex TBA[Ir(dfppy)₂(NCS)₂] (1) were reported. 1 can selectively detect Hg²⁺ with the help of UV-Vis absorption and emission spectra titration. In the presence of Hg²⁺, the obvious decrease of the luminescence intensity at 475 nm was investigated, which could be observed by the naked eyes. The phosphorescence quantum efficiency in CH₃CN solution changed from 0.07 to 0.00085. No obvious spectra changes were observed upon addition of a large excess of other transition metals. Due to its strong thiophilic affinity, the special chemical reaction induced by Hg²⁺ is responsible for the significant change of absorption and luminescence spectra, which is confirmed by ESI-MS.     

Reactions of thioether carboxylic acids with mercury(II). Formation and X-ray crystal structure of mercury(II) mercaptoacetate

Reactions of Hg(II) salts with thioether carboxylic acids o-C₆H₄[CH(SCH₂COOH)₂]₂ (1a) and PhCH(SCH₂COOH)₂ (3) in water were found to lead to the decomposition of these ligands with the formation of mercury(II) mercaptoacetate Hg(SCH₂COOH)₂ (2) and aldehydes o-C₆H₄(CHO)₂ and PhCHO, respectively. A similar reaction was observed between Hg(NO₃)₂ and CH₃(CH₂)₂CH(SCH₂COOH)₂ (4). The X-ray structure of Hg(SCH₂COOH)₂ (2) shows a linear -S-Hg-S- moiety. The mechanism of the formation of 2 in the reactions between Hg²⁺ and thioether carboxylic acids in water is discussed.     

Synthesis and X-ray structures of triphenylphosphine-mercury(II) thiosalicylate complexes: novel aggregation processes

Reaction of [HgCl₂(PPh₃)₂] with one equivalent of thiosalicylic acid (tsalH₂, HSC₆H₄CO₂H) and excess triethylamine, followed by recrystallisation from dichloromethane-diethyl ether gives the compound [Hg₂(tsal)₂(PPh₃)₂] (2). This has a bis(S,O)-chelated mercury centre with a nido-trigonal bipyramidal coodination, with the four oxygens of the two carboxylates also coordinated to a Hg(PPh₃)₂ moiety. When a reduced quantity of pyridine was used as the base a different crystalline product was isolated. This was characterised as [Hg₂(tsal)₂(PPh₃)₂][Hg(tsalH)₂] (3), which contains the same [Hg₂(tsal)₂(PPh₃)₂] moiety found for 2, co-crystallised with a [Hg(tsalH)₂]. The two mercury-thiosalicylate species are connected by means of O-H?O hydrogen bonding.