Mononuclear Mercury Research Articles

Synthesis, crystallographic studies, antibacterial and antifungal activities of mononuclear mercury(II) complexes derived from [PPh2(CH2)nPPh2CH2C(O)C6H4Cl)]Br ligands

This account describes our recent studies on zwitterionic mercury(II) complexes with two diphosphonium salts, [PPh2(CH2)nPPh2CH2C(O)C6H4Cl)]Br (n = 1 (S1) and 2 (S2)), derived from 1,2-bis(diphenyl-phosphino)methane (dppm) and 1,2-bis(diphenyl-phosphino)ethane (dppe). These complexes were synthesized through reactions between diphosphonium salts and HgX2 in equimolar ratio and characterized by elemental analysis, IR, 1H, 13C and 31P NMR spectroscopic methods. The structure of complex [HgI2Br(PPh2(CH2)2PPh2CH2C(O)C6H4Cl)] (6) was determined by a single crystal X-ray structural analysis. The results indicated that the mercury center in this complex is four-coordinated in a distorted tetrahedral configuration. The results confirmed that the coordination of ligand to metal occurred through the phosphine group (P-coordination mode). Furthermore, antibacterial/antifungal activities of the diphosphonium ligands and their complexes were tested against two Gram-negative bacteria Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 9027) and two Gram-positive bacteria Staphylococcus aureus (ATCC 6538) and Bacillus subtilis (ATCC 6633) as well as two fungi (Geotrichum sp. and Candida albicans). It seems that the chemical compounds reported herein may be used for control of pathogenic bacteria/fungi.

Cleavage of Hg-C Bonds of Organomercurials Induced by ImOHSe via Two Distinct Pathways.

We show that the N-methylimidazole-based selone ImOHSe having an N-CH2CH2OH substituent has the remarkable ability to degrade methylmercury by two distinct pathways. Under basic conditions, ImOHSe converts MeHgCl into biologically inert HgSe nanoparticles and Me2Hg via the formation of an unstable intermediate (MeHg)2Se (pathway I). However, under neutral conditions, in the absence of any base, ImOHSe facilitates the cleavage of the Hg-C bond of MeHgCl at room temperature (23 °C), leading to the formation of a stable cleaved product, the tetracoordinated mononuclear mercury compound (ImOHSe)2HgCl2 and Me2Hg (pathway II). The initial rate of Hg-C bond cleavage of MeHgCl induced by ImOHSe is almost 2-fold higher than the initial rate observed by ImMeSe. Moreover, we show that ImYSe (Y = OH, Me) has an excellent ability to dealkylate Me2Hg at room temperature. Under acidic conditions, in the presence of excess ImYSe, the volatile and toxic Me2Hg further decomposes to the tetracoordinated mononuclear mercury compound [(ImYSe)4Hg]2+. In addition, the treatment of ImOHSe with MeHgCys or MeHgSG in phosphate buffer (pH 8.5) afforded water-soluble Hg(SeS) nanoparticles via unusual ligand exchange reactions, whereas its derivative ImOMeSe or ImMeSe, lacking the N-CH2CH2OH substituent, failed to produce Hg(SeS) nanoparticles under identical reaction conditions.

Activation of the Hg–C Bond of Methylmercury by [S2]-Donor Ligands

Here we report that [S2]-donor ligands BmmOH, BmmMe, and BmeMe bind rapidly and reversibly to the mercury centers of organomercurials, RHgX, and facilitate the cleavage of Hg-C bonds of RHgX to produce stable tetracoordinated Hg(II) complexes and R2Hg. Significantly, the rate of cleavage of Hg-C bonds depends critically on the X group of RHgX (X = BF4-, Cl-, I-) and the [S2]-donor ligands used to induce the Hg-C bonds. For instance, the initial rate of cleavage of the Hg-C bond of MeHgI induced by BmeMe is almost 2-fold higher than the initial rate obtained by BmmOH or BmmMe, indicating that the spacer between the two imidazole rings of [S2]-donor ligands plays a significant role here in the cleavage of Hg-C bonds. Surprisingly, we noticed that the initial rate of cleavage of the Hg-C bond of MeHgI induced by BmeMe (or BmmMe) is almost 10-fold and 100-fold faster than the cleavage of Hg-C bonds of MeHgCl and [MeHg]BF4 respectively, under identical reaction conditions, suggesting that the Hg-C bond of [MeHg]BF4 is highly inert at room temperature (21 °C). We also show here that the nature of the final stable cleaved products, i.e. Hg(II) complexes, depends on the X group of RHgX and the [S2]-donor ligands. For instance, the reaction of BmmMe with MeHgCl (1:1 molar ratio) afforded the formation of the 16-membered metallacyclic dinuclear mercury compound (BmmMe)2Hg2Cl4, in which the two Cl atoms are located inside the ring, whereas due to the large size of the I atom, a similar reaction with MeHgI yielded polymeric [(BmmMe)2HgI2]m·(MeHgI)n. However, the treatment of BmmMe with ionic [RHg]BF4 led to the formation of the tetrathione-coordinated mononuclear mercury compound [(BmmMe)2Hg](BF4)2, where BF4- serves as a counteranion.

Mononuclear mercury(II) complexes containing bipyridine derivatives and thiocyanate ligands: Synthesis, characterization, crystal structure determination, and luminescent properties

A series of mercury(II) complexes, [Hg(NN)(SCN)2] (NN is 4,4′-dimethyl-2,2′-bipyridine in 1, 5,5′-dimethyl-2,2′-bipyridine in 2, 6,6′-dimethyl-2,2′-bipyridine in 3 and 6-methyl-2,2′-bipyridine in 4), were prepared from the reactions of Hg(SCN)2 with mentioned ligands in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurement by methanol diffusion into a DMSO solution. The four complexes were thoroughly characterized by spectral methods (IR, UV–Vis, 13C{1H}NMR, 1H NMR and luminescence), elemental analysis (CHNS) and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the mercury(II) cation is four-coordinated in a distorted tetrahedral configuration by two S atoms from two thiocyanate anions and two N atoms from one chelating 2,2′-bipyridine derivative ligand. Also, in these complexes intermolecular interactions, for example CH⋯N hydrogen bonds (in 1–4), CH⋯S hydrogen bonds (in 1, 2 and 4), π … π interactions (in 2–4), Hg⋯N interactions (in 2) and S⋯S interactions (in 4), are effective in the stabilization of the crystal structures and the formation of the 3D supramolecular complexes. Furthermore, the luminescence spectra of the title complexes show that the intensity of their emission bands are stronger than the emission bands for the free bipyridine derivative ligands.

Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a Benzothiazole-Attached Macrocycle That Correlate with Structural Coordination Modes.

We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO2S2-macrocycle L was synthesized, and its mercury(II) selectivity (for perchlorate salt) as a dual-probe channel (UV-vis and fluorescence) chemosensor exhibiting the largest blue shift and the fluorescence turn-off was observed. In the mercury(II) sensing with different anions, except ClO4(-) and NO3(-), no responses for mercury(II) were observed with other anions such as Cl(-), Br(-), I(-), SCN(-), OAc(-), and SO4(2-). A crystallographic approach for the mononuclear mercury(II) perchlorate complex [Hg(L)(ClO4)2]·0.67CH2Cl2 (1) and polymeric mercury(II) iodide complex [Hg(L)I2]n (2) revealed that the observed anion-controlled mercury(II) sensing in the fluorescence mainly stems from the endo- and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg-Ntert bond formation or not. The detailed complexation process with mercury(II) perchlorate associated with the cation sensing was also monitored with the titration methods by UV-vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry.

Fluorescence and crystal structures of new mercury(II) macrocyclic N-heterocyclic carbene complexes with ether chains

Polyerther-linked mercury(II) carbene complexes are synthesized by the reaction of carbene precursores with mercury(II) acetate. The binuclear carbene complexes with the chloride ion linkage are easily prepared by the reaction of mononuclear mercury carbene complexes with tetrabutylammoium chloride. The crystal structures reveal that the fluorescence of mercury complexes are related to the coordination mode of the ligands.

Effect of pyridyl substituents leading to the formation of green luminescent mercury(ii) coordination polymers, zinc(ii) dimers and a monomer

Pyridine-2, -3 and -4 functionalized dithiocarbamate ligands yielded the coordination polymers with mercury, namely [{Hg(L)2}n] (L = L1, C5H4NCH2NCS2CH2C7H5O2 (1); L2, C5H4NCH2NCS2CH3 (2); L3, C5H4NCH2NCS2CH2C4H3O (3); and L4, C5H4NCH2NCS2CH2CH2C6H5 (4)), [PhHg(L3)] (5), and mononuclear [Hg(L5)2], L5 = C5H4NCH2NCS2CH2C6H5 (6). Unexpectedly, the pyridine-2-functionalized ligand, L6, C5H4NCH2NCS2CH2C6H5 gave a cyclized product, benzyl-2H-imidazo[1,5-a]pyridine-3-thione (7), C14H13N2S, instead of a mercury complex. Complexes with zinc were also characterized, namely dinuclear [Zn2(L5)4] (8) and [Zn2(L7)4], L7 = CH3CH2O2C5H9NCS2 (9) and a mononuclear complex [Zn(L8)2], L8 = C4H3NCH3CH2NCS2CH2C6H5 (10). These ten compounds have been characterized by microanalysis and X-ray crystallography. Complexes (1, 2) and 3 are 1-D and 2-D coordination polymers in which the ligands are uniquely bonded in the bridging-chelating mode in a μ2, κ3-N, S, S fashion establishing square pyramidal five-coordinate and octahedral six-coordinate geometries about the Hg atom respectively. The structure of 4 is also a 1-D coordination polymer formed via bridging sulphur bonds with a five-coordinate distorted geometry about the mercury atom. 6 is a mononuclear mercury(II) complex forming an interesting polymeric 1-D architecture through intermolecular Hg⋯S interactions. 8 is the first example of a homoleptic dinuclear zinc(II) dithiocarbamate complex bridged through ligand L5 in a μ2, κ3-N, S(11), S(13) bridging-chelating manner. L7 and L8 form a typical S, S-bridged dimer 9 and a mononuclear complex 10. The nature of the Hg–N and Zn–N bonds in the coordination polymers 1, 2 and 3 and in the dinuclear 8 has been assessed by DFT calculations. Complexes 1–9 are luminescent in both solution and solid phases; especially, significant red shifted green emission in the solid phase for the coordination polymers 1, 2 and 3 shows good structure–property correlations.

Synthesis, characterization, and molecular and crystalline architectures of two mononuclear mercury(II) iodide complexes containing two tridentate Schiff bases as end-capping ligands

Synthesis, characterization, and molecular and crystalline architectures of two mononuclear mercury(II) iodide complexes containing two tridentate Schiff bases as end-capping ligands

Diiodo{N,N′-Bis(2,3,4-trimethoxybenzaldehyde)-ethylenediimine}mercury(II): Synthesis and crystal structure

Mononuclear mercury(II) complex [Hg((2,3,4-MeO-Ba)2En)I2] (I), where (2,3,4-MeO-Ba)2En = N,N′-bis(2,3,4-trimethoxybenzaldehyde)ethylenediimine, has been synthesized and characterized by elemental analysis (C, H, and N) and confirmed by single-crystal X-ray diffraction analysis. The complex I crystallizes in the monoclinic system, with space group C2/c, having one symmetry-independent Hg2+ ion coordinated in distorted tetrahedral geometry by two N atoms of the Schiff base ligand and by two I atoms. The Schiff base ligand (2,3,4-MeO-Ba)2En acts as a chelating ligand and coordinates via two N atoms to the mercury center and adopts an (E,E) conformation.

New complex of mercury(II) with Schiff base derived from A-methylcinnamaldehyde and ethylenediamine

The new mononuclear mercury(II) complex [Hg((Me-Ca)2En)Br2] (I), where (Me-Ca)2En = N, N,N′-bis[(E)-2-benzylidenepropylidene]ethane-1,2-diamine, has been synthesized and characterized. The crystal and molecular structure of I was determined by X-ray crystallography from single-crystal data. The complex I crystallizes in the monoclinic system, having one symmetry-independent Hg2+ ion coordinated in distorted tetrahedral geometry by two N atoms of the Schiff base ligand and by two Br atoms. This structure contains intermolecular non-classical hydrogen bonds of the type C-H...Br.

New N-heterocyclic carbene mercury(II) complexes: Close mercury–arene interaction

Mononuclear mercury complexes ( 1, 2, and 3) bearing bis- N-heterocyclic carbene (NHC) ligands of the form [(NHC) 2-μ-Hg] +2 have been prepared and structurally characterised. The complexes were derived from three bis-imidazolium salts as precursors to NHC; either 1,3-bis( N-methylimidazolium-1-ylmethyl)benzene bis(hexafluorophosphate) ( I·2PF 6), 1,3-bis( N-butylimidazolium-1-ylmethyl)benzene bis(hexafluorophosphate) ( II·2PF 6) or 3,5-bis( N-butylimidazolium-1-ylmethyl)toluene bis(hexafluorophosphate) ( III·2PF 6) treated with mercury(II) acetate. Interestingly X-ray crystal structure analysis revealed a close interaction between the Hg metal centre with one carbon atom of the aryl linker in addition to coordination with two NHCs.

Aromatic N-oxides in construction of different carboxylate coordination polymers of zinc(II), cadmium(II) and mercury(II)

The coordination polymers [Zn(C 6H 5COO) 2(PNO)] n ( 1), [Zn 2(C 6H 5COO) 4(4,4′-BPNO)] n ( 2), [Zn 4(C 6H 4C 2O 4) 4(4,4′-BPNO) 2(H 2O) 5] n · nH 2O ( 3), [Cd(C 6H 5COO) 2(PNO)] n ( 4), [Cd 3(C 6H 5COO) 6(4,4′-BPNO) 2] n·2 nH 2O ( 5), [Cd(C 6H 4C 2O 4)(4,4′-BPNO)(H 2O)] n ( 6) and [Hg(C 6H 5COO) 2(4,4′-BPNO) 2] n ( 7), (where PNO = pyridine N-oxide, 4,4′-BPNO = 4,4′-bipyridyl- N,N′-dioxide) are synthesized and structurally characterized. The structures of these coordination polymers exhibit mononuclear to trinuclear nodes built by ligation of carboxylate to metal ions connected by N-oxide ligands. Pyridine N-oxide interconnects metal nodes by acting as μ 2-bridging ligand in complexes 1, and 4. In the linear coordination polymer 2, the paddle wheel structure of zinc(II) benzoate units are interconnected by 4,4′-bipyridyl- N,N′-dioxide which acts as a bidentate spacer ligand adopting a trans μ 2–η 1 : η 1 coordination mode. The polymeric structure of 3 formed by terephthalate and 4,4′-bipyridyl- N,N′-dioxide with zinc(II) contains self-assembled dinuclear Zn 2O 2 type of carboxylate cores, with 4,4′-bipyridyl- N,N′-dioxide coordinating through cis μ 2–η 1 : η 1 coordination mode. The cadmium coordination polymer 5, comprising of 4,4′-bipyridyl- N,N′-dioxide and benzoate, has trinuclear cadmium benzoate cores wherein the terminal cadmium ions are interconnected by monodentate 4,4′-bipyridyl- N,N′-dioxide bridges. The coordination polymer 6 comprises of mononuclear cadmium nodes independently bridged by terephthalate and 4,4′-bipyridyl- N,N′-dioxide thereby leading to a 3-fold interpenetrated three dimensional network. Double helical polymeric structure is observed in the coordination polymer 7 derived from mononuclear mercury(II) benzoate nodes bridged by 4,4′-bipyridyl- N,N′-dioxide with cis μ 2–η 1 : η 1 coordination mode.

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, Ph 2PCH 2PPh 2 C(H)C(O)(C 6H 4Cl) ( 2) with mercury(II) halides in equimolar ratios using dry methanol as solvent yielded the P, C-chelated complexes, {HgX 2[Ph 2PCH 2PPh 2C(H)C(O)(C 6H 4Cl)]} 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.

Exploring a series of monoethynylfluorenes as alkynylating reagents for mercuric ion: Synthesis, spectroscopy, photophysics and potential use in mercury speciation

New luminescent mononuclear mercury(II) mono- and dialkynylated complexes containing substituted fluorene and fluorenone units [R–C C–HgCH 3] and [R–C C–Hg–C C–R] (R = 9,9-dialkylfluorene-2-yl and fluoren-9-one-2-yl; alkyl = H, ethyl, hexyl, octyl, hexadecyl) were prepared in good yields by mercuration of terminal acetylene R–C CH with CH 3HgCl and HgCl 2 at room temperature via the dehydrohalogenation reaction. The structures of these organomercurial compounds were characterized by IR and NMR spectroscopies, elemental analysis and FAB mass spectrometry. Their optical and photoluminescence spectra were also studied. The structural features of one complex was elucidated by X-ray crystallography in which there is an indication of weak mercuriophicity among the molecules in the solid state. A new protocol is developed for derivatization of inorganic mercury(II) ion into dialkynyl mercury(II) compounds followed by the ready extraction into dichloromethane, which can be analyzed by HPLC technique using UV detection. These results have important implications in the development of analytical procedures for the determination of mercuric ion in aqueous solutions.

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

Synthesis of the novel ligand ferrocenyliminophosphine [(η 5-C 5H 5)Fe{(η 5-C 5H 4)CH N(C 6H 4-2-PPh 2)}] ( 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 HgCl 2L 2 ( 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.

Complexation of 4,4′-di( tert-butyl)-5-ethynyl-2,2′-bithiazole with mercury(II) ion: Synthesis, structures and analytical applications

Two new mononuclear mercury(II) alkynyl complexes containing substituted bithiazole unit [R–C C–HgMe] ( 2) and [R–C C–Hg–C C–R] ( 3) (R = 4,4′-di( tert-butyl)-2,2′-bithiazol-5-yl) were prepared in good yields by mercuration of 4,4′-di( tert-butyl)-5-ethynyl-2,2′-bithiazole ( 1) at room temperature via the dehydrohalogenation reaction of MeHgCl and HgCl 2 with terminal acetylene R–C CH. The structures of the title compounds were characterized by NMR and IR spectroscopy, FAB mass spectrometry, X-ray crystallography and luminescence spectra. A new protocol for derivatization of inorganic and organic mercury(II) ions to mono- and dialkynyl mercury(II) compounds followed by extraction into dichloromethane is suggested, which can be effectively analyzed by HPLC technique using UV detection. The proposed procedure can offer a new opportunity for the simultaneous determination of inorganic Hg(II) and MeHg(II) in aqueous solutions.

Mercury complexes of meso-tetra-(p-cyanophenyl)porphyrin and N-methylporphyrin: meso-tetra(p-cyanophenyl)porphyrinatomercury(II) and chloro(N-methyl-meso- tetraphenylporphyrinato)mercury(II).

This work for the first time reports X-ray crystals of the two mononuclear mercury(II) porphyrin complexes, i.e., a four-coordinate complex Hg(p-CN)4tpp (1) and a five-coordinate complex Hg(N-Me-tpp)Cl (2). Compound 1 is distorted square planar, whereas compound 2 is trigonal bipyramidal distorted square-based pyramid in which the apical site is occupied by a N(1) atom.