Determination of mercury species by the diffusive gradient in thin film technique and liquid chromatography – atomic fluorescence spectrometry after microwave extraction

A diffusive gradient in thin films technique (DGT) was combined with liquid chromatography (LC) and cold vapor atomic fluorescence spectrometry (CV-AFS) for the simultaneous quantification of four mercury species (Hg²⁺, CH₃Hg⁺, C₂H₅Hg⁺, and C₆H₅Hg⁺). After diffusion through an agarose diffusive layer, the mercury species were accumulated in resin gels containing thiol-functionalized ion-exchange resins (Duolite GT73, and Ambersep GT74). A microwave-assisted extraction (MAE) in the presence of 6 M HCl and 5 M HCl (55 °C, 15 min) was used for isolation of mercury species from Ambersep and Duolite resin gels, respectively. The extraction efficiency was higher than 95.0% (RSD 3.5%). The mercury species were separated with a mobile phase containing 6.2% methanol + 0.05% 2-mercaptoethanol + 0.02 M ammonium acetate with a stepwise increase of methanol content up to 80% in the 16th min on a Zorbax C18 reverse phase column. The LODs of DGT–MAE–LC–CV-AFS method were 38 ng L⁻¹ for CH₃Hg⁺, 13 ng L⁻¹ for Hg²⁺, 34 ng L⁻¹ for C₂H₅Hg⁺ and 30 ng L⁻¹ for C₆H₅Hg⁺ for 24 h DGT accumulation at 25 °C.     

Reaction chemistry of tricarbonyl-η-pentadienylmanganese: Straightforward synthesis of stable manganese carbonyl terminal thiolates and a dinuclear bis(ethylenediaminyl) complex

Tricarbonyl-η⁵-pentadienylmanganese reacts with mercaptans RSH, R = Ph, C₆F₅, m-NH₂C₆H₄, p-NH₂C₆H₄, and HSCH₂CH₂ in the presence of ECH₂CH₂E, E = -PPh₂ or -NH₂ to give novel stable terminal thiolate mononuclear complexes fac-Mn(CO)₃(SR)(Ph₂PCH₂CH₂PPh₂-κ²-P,P′) for R = Ph, C₆F₅, m-NH₂C₆H₄, p-NH₂C₆H₄, and HSCH₂CH₂ and fac-Mn(CO)₃(SR)(H₂NCH₂CH₂NH₂-κ²-N,N′) for R = Ph and C₆F₅. Upon reaction of tricarbonyl-η⁵-pentadienylmanganese with ethylenediamine a dinuclear complex [fac-Mn(CO)₃(μ-H₂NCH₂CH₂NH-κ²-N,N′)]₂ was formed wherein the diaminyl ligand functions in the capacity of chelating and bridging ligand.     

Two novel 18-metallacrown-6 complexes: Synthesis,structural characterization and bioactivity

Two new macrocyclic hexanuclear metal(III) 18-metallacrowns-6, [Mn₆(acshz)₆(H₂O)₆] · 18H₂O (1) and [Fe₆(acshz)₆(CH₃OH)₆] · 6CH₃OH · 6H₂O (2), have been synthesized and characterized, where acshz³⁻ is N-acetyl-5-chlorosalicylhydrazidate. These crystal structures contain neutral 18-membered metallacrown rings consisting of six metal(III) ions and six acshz³⁻ ligands. The ring is formed by the succession of six structural moieties of the type [M(III)–N–N] through hydrazide N–N groups bridging the ring metal ions. The ligand enforces the metal ions to form the stereochemistry of a propeller configuration with alternate Λ/Δ or Δ/Λ forms. The largest diameters of the hexanuclear rings are about 6.97 Å at the entrance and 9.53 Å at the centre of the cavity for 1; and 7.94 and 10.24 Å for 2, respectively. The solution integrity and stability of the metallacrowns were confirmed using electrospray ionization ESI-MS and UV–Vis spectroscopy in methanol. Antibacterial screening data indicate the formation of the metallacrown 1 reduces the antimicrobial activity of the ligand H₃acshz hugely, while metallacrown 2 has strong antimicrobial activity against Bacillus subtilis (B. subtilis).     

New synthetic and structural studies on nitroso-ortho-carboranes RCB10H10CNO and bis(ortho-carboranyl)amines (RCB10H10C)2NH (R = Ph or Me)

Improved procedures are reported for the preparation of nitroso-carboranes RCb°NO (Cb° = 1,2-C₂B₁₀H₁₀; R = Ph, Me at cage carbon C2) in 44–77% yield, and of dicarboranylamines (RCb°)₂NH in 55–65% yield by reactions between the lithio-carboranes, RCb°Li and nitrosyl chloride, NOCl, in cold mixtures of diethyl ether and either pentane (for RCb°NO) or dimethoxyethane (for (RCb°)₂NH). Deprotonation of the amines by KO^tBu in toluene in the presence of 18-crown-6, (CH₂CH₂O)₆, affords the salts [K(18-crown-6)]⁺[(RCb°)₂N]⁻. X-ray crystal structures of PhCb°NO, (PhCb°)₂NH, (MeCb°)₂NH and [K(18-crown-6)]⁺[(PhCb°)₂N]⁻ are described, and the bonding implications of their cage C…C distances (1.68, 1.80, 1.75 and 1.99 Å, respectively) are discussed. These species provide further striking examples of the remarkable capacity of the ortho-carborane cage to act as a sensitive indicator of the π-donor characteristics of ligands attached to its cage carbon atoms.     

Application of capillary affinity electrophoresis and density functional theory to the investigation of valinomycin–lithium complex

Capillary affinity electrophoresis (CAE) and quantum mechanical density functional theory (DFT) have been applied to the investigation of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with lithium cation Li⁺. Firstly, from the dependence of effective electrophoretic mobility of Val on the Li⁺ ion concentration in the background electrolyte (BGE) (methanolic solution of 50 mM chloroacetic acid, 25 mM Tris, pH_MeOH 7.8, 0–40 mM LiCl), the apparent binding (stability) constant (K_b) of Val–Li⁺ complex in methanol was evaluated as log K_b = 1.50 ± 0.24. The employed CAE method include correction of the effective mobilities measured at ambient temperature, at different input power (Joule heating) and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25 °C and to the constant ionic strength 25 mM. Secondly, using DFT calculations, the most probable structures of the non-hydrated Val–Li⁺ and hydrated Val–Li⁺·3H₂O complex species were predicted.     

Ab initio/DFT theory and multichannel RRKM study on the mechanisms and kinetics for the CH3S + CO reaction

The potential energy surface for the reaction of CH₃S with CO was calculated at the G3MP2//B3LYP/6-311++G(d,p) level. The rate constants for feasible channels leading to several products were calculated by TST and multichannel-RRKM theory. The results show that addition–elimination mechanism is dominant, while hydrogen abstraction mechanism is uncompetitive. The major channel is the addition of CO to CH₃S leading to an intermediate CH₃SCO which then decomposes to CH₃ + OCS. In the temperature range of 200–3000 K, the overall rate constants are positive temperature dependence and pressure independence, and it can be described by the expression as k = 1.10 × 10⁻¹⁶T^1.57exp(−3359/T) cm³ molecule⁻¹ s⁻¹. At temperature between 208 and 295 K, the calculated rate constants are in good agreement with the experimental upper limit data. At T = 1000 and 2000 K, the major product is CH₃ + OCS at lower pressure; while at higher pressure, the stabilization of IM1 is dominant channel.     

Structural and selectivity of 18-crown-6 ligand in lanthanide-picrate complexes

The selectivity factor in the separation of lanthanide could be associated with the coordination behaviour. Thus, we observed the study in the solid phase to understand the coordination pattern of Ln(III) with the 18-crown-6 (18C6) ligand. Good selectivity of the rigid 18C6 ligand toward Ln(III) depends on gradually smaller their ionic radii of Ln(III) in the complexes formation in the presence of picrate anion (Pic⁻), i.e. lanthanide contraction and steric effects as clearly shown in the series of [Ln(Pic)₂(18C6)]⁺(Pic)⁻ {Ln = La, Ce, Pr, Nd, Sm, Gd} and [Ln(Pic)₃(OH₂)₃] · 2(18C6) · 4H₂O {Ln = Tb, Ho} complexes. The La-Gd complexes crystallized in an orthorhombic with space group Pbca, while the Ho complex crystallized in triclinic with space group . The lighter lanthanides complexes [La-Sm] had a 10-coordination number from the 18C6 ligand and the two picrates, forming a bicapped square-antiprismatic geometry. Meanwhile, the middle lanthanide complex [Gd] had a nine-coordination number from the 18C6 ligand and the two picrates, forming a tricapped trigonal prismatic geometry. The heavier lanthanide [Ho] is rather unique, since Ho(III) coordinated with nine oxygen atoms from three picrates and three water molecules in the opposite direction whereas three 18C6 molecules surrounded in the inner coordination sphere, forming a trigonal tricapped prismatic geometry. The 18C6 ligand is effective in controlling the molecular geometry and coordination bonding of Ln-O and can use a crystal engineering approach. No dissociation of Ln-O bonds in solution was observed in NMR studies conducted at different temperatures. The photoluminescence spectrum of the Pr complex has typical 4f-4f emission transitions, i.e. ³P₀ → ³F₂ (650 nm), ¹D₂ → ³F₂ (830 nm) and ¹D₂ → ³F₄ (950 nm).     

Revision of iron(III)–citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies

A detailed study of iron (III)–citrate speciation in aqueous solution (θ = 25 °C, I_c = 0.7 mol L⁻¹) was carried out by voltammetric and UV–vis spectrophotometric measurements and the obtained data were used for reconciled characterization of iron (III)–citrate complexes. Four different redox processes were registered in the voltammograms: at 0.1 V (pH = 5.5) which corresponded to the reduction of iron(III)–monocitrate species (Fe:cit = 1:1), at about −0.1 V (pH = 5.5) that was related to the reduction of FeL₂⁵⁻, FeL₂H⁴⁻ and FeL₂H₂³⁻ complexes, at −0.28 V (pH = 5.5) which corresponded to the reduction of polynuclear iron(III)–citrate complex(es), and at −0.4 V (pH = 7.5) which was probably a consequence of Fe(cit)₂(OH)_x species reduction. Reversible redox process at −0.1 V allowed for the determination of iron(III)–citrate species and their stability constants by analyzing E_p vs. pH and E_p vs. [L⁴⁻] dependence. The UV–vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (log β = 25.69), FeL₂H₂³⁻ (log β = 48.06), FeL₂H⁴⁻ (log β = 44.60), and FeL₂⁵⁻ (log β = 38.85). The stability constants obtained by spectrophotometry were in agreement with those determined electrochemically. The UV–vis spectra recorded at various citrate concentrations (pH = 2.0) supported the results of spectrophotometric–potentiometric titration.     

Tuning the selectivity of polymeric ionic liquid sorbent coatings for the extraction of polycyclic aromatic hydrocarbons using solid-phase microextraction

A new generation polymeric ionic liquid (PIL), poly(1-4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (poly(VBHDIm⁺ NTf₂⁻)), was synthesized and is shown to exhibit impressive selectivity towards the extraction of 12 polycyclic aromatic hydrocarbons (PAHs) from aqueous samples when used as a sorbent coating in direct-immersion solid-phase microextraction (SPME) coupled to gas chromatography (GC). The PIL was imparted with aromatic character to enhance π–π interactions between the analytes and the sorbent coating. For comparison purposes, a PIL with similar structure but lacking the π–π interaction capability, poly(1-vinyl-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide) (poly(HDIm⁺ NTf₂⁻)), as well as a commercial polydimethylsiloxane (PDMS) sorbent coating were evaluated and exhibited much lower extraction efficiencies. Extraction parameters, including stir rate and extraction time, were studied and optimized. The detection limits of poly(VBHDIm⁺ NTf₂⁻), poly(HDIm⁺ NTf₂⁻), and PDMS coatings varied between 0.003–0.07 μg L⁻¹, 0.02–0.6 μg L⁻¹, and 0.1–6 μg L⁻¹, respectively. The partition coefficients (log K_fs) of eight PAHs to the three studied fiber coatings were estimated using a static SPME approach. This study represents the first report of analyte partition coefficients to any PIL-based material.     

Theoretical study on the reaction mechanism of CH4 with CaO

The reaction pathways and energetics for the reaction of methane with CaO are discussed on the singlet spin state potential energy surface at the B3LYP/6-311+G(2df,2p) and QCISD/6-311++G(3df,3pd)//B3LYP/6-311+G(2df,2p) levels of theory. The reaction of methane with CaO is proposed to proceed in the following reaction pathways: CaO + CH₄ → CaOCH₄ → [TS] → CaOH + CH₃, CaO + CH₄ → OCaCH₄ → [TS] → HOCaCH₃ → CaOH + CH₃ or [TS] → CaCH₃OH → Ca + CH₃OH, and OCaCH₄ → [TS] → HCaOCH₃ → CaOCH₃ + H or [TS] → CaCH₃OH → Ca + CH₃OH. The gas-phase methane–methanol conversion by CaO is suggested to proceed via two kinds of important reaction intermediates, HOCaCH₃ and HCaOCH₃, and the reaction pathway via the hydroxy intermediate (HOCaCH₃) is energetically more favorable than the other one via the methoxy intermediate (HCaOCH₃). The hydroxy intermediate HOCaCH₃ is predicted to be the energetically most preferred configuration in the reaction of CaO + CH₄. Meanwhile, these three product channels (CaOH + CH₃, CaOCH₃ + H and Ca + CH₃OH) are expected to compete with each other, and the formation of methyl radical is the most preferable pathway energetically. On the other hand, the intermediates HCaOCH₃ and HOCaCH₃ are predicted to be the energetically preferred configuration in the reaction of Ca + CH₃OH, which is precisely the reverse reaction of methane hydroxylation.     

Formation and crystal structures of [(alkoxy)bis(pyridin-2-yl)methanolato-N,O,N]tin(IV) complexes

Reactions of bis(pyridin-2-yl)ketone with tin tetrahalides, SnX₄ (X = Cl or Br), or organotin trichlorides, R^′SnCl₃ (R^′ = Ph, Bu or CH₂CH₂CO₂Me), in ROH (R = Me or Et) readily produces RObis(pyridin-2-yl)methanolato)tin complexes, [5: RO(py)₂C(OSnX₃)] (5: R,X = Me,Cl; Et,Cl; Et,Br) or [6: MeO(py)₂C(OSnCl₂R^′)] (R^′ = Ph, Bu, CH₂CH₂CO₂Me). In addition, halide exchange reaction between SnI₄ and (5: R,X = Me,Cl) occurred to give (5: R,X = Me,I). The crystal structures of six tin(IV) derivatives indicated, in all cases, a monoanionic tridentate ligand, [RO(py)₂C(O⁻)-N,O,N], arranged in a fac manner about a distorted octahedral tin atom. The Sn–O and Sn–N bonds lengths do not show much variation amongst the six complexes despite the differences in the other ligands at tin.     

Iron(III) complexes of the tris-(3-aminopropyl) derivative of a 14-membered tetraazamacrocycle: Potentiometric,spectroscopic and electrochemical studies

The properties of the iron(III) complexes of the ditopic macrocyclic ligand with three aminopropyl pendant arms, L¹ = 3,7,11-tris-(3-aminopropyl)-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene were investigated in aqueous solution. Potentiometric studies indicated the presence of mononuclear [FeH_hL¹]^h+3 (h = 0–3), and dinuclear [Fe₂L¹]⁶⁺, [Fe₂L¹(OH)]⁵⁺ and [Fe₂L¹(OH)₂]⁴⁺ complexes, and their stability constants were determined at 298.2 K and ionic strength 0.10 mol dm⁻³ in KNO₃. The log K values of mononuclear protonated species indicated the consecutive deprotonation of the aminopropyl arms, suggesting the nitrogen donor atoms from the macrocycle as the preferred coordination environment for the first metal centre, and the amines from the pendant arms for the second one. The dinuclear complex is formed at about 85% of the total amount of the metal ion for 2:1 Fe:L¹ ratio solutions at pH 4.0–4.5. The log K values of the deprotonation of dinuclear hydrolysed species are consistent with the presence of two water molecules directly bound to the metal centres. Spectroscopic UV–Vis and IR data for 2:1 Fe³⁺:L¹ ratio samples confirmed the existence of dinuclear and hydroxo dinuclear species. EPR spectra of these solutions were interpreted by an equilibrium of two high-spin d⁵ state of iron(III) species with different rhombic E/D distortions. Electrochemical studies also established the formation of mono- and dinuclear complexes, showing irreversible redox behaviour. The two metal centres on the dinuclear complexes have only weak interactions.     

Synthesis and properties of a new ketoiminate derivative of the 2,2,6,6-tetramethylheptane-3,5-dionate ligand to prepare volatile CVD precursors

The β-ketoimine (CH₃)₃CC(NH₂)CHC(O)C(CH₃)₃ (1) was synthesized by amination with dry ammonia in the presence of TiCl₄. M.p. = 131 °C. IR and ¹H and ¹³C NMR spectroscopic characterization indicates that the structure of a solution of 1 is the ketone form, and a single-crystal X-ray diffraction study shows that the structure of 1 is the enaminoketone form. The reaction of 1 with copper(II) and nickel(II) salts in solution gave chelate metal complexes: Cu[(CH₃)₃CC(NH)CHC(O)C(CH₃)₃]₂ (2), M.p. = 209 °C, and Ni[(CH₃)₃CC(NH)CHC(O)C(CH₃)₃]₂ (3), M.p. = 267 °C. These complexes are volatile and sublime at 180–190 °C at 5 × 10⁻³ Torr. An X-ray diffraction study reveals that these metal complexes are monomeric and isostructural in the solid state. In compound 2, the Cu atom has a square coordination environment: Cu–O ≈ Cu–N = 1.91 Å, ∠O–Cu–N = 91.81 Å.     

Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit

Two stereoisomers of cis-[Ru(bpy)(pynp)(CO)Cl]PF₆ (bpy = 2,2′-bipyridine, pynp = 2-(2-pyridyl)-1,8-naphthyridine) were selectively prepared. The pyridyl rings of the pynp ligand in [Ru(bpy)(pynp)(CO)Cl]⁺ are situated trans and cis, respectively, to the CO ligand. The corresponding CH₃CN complex ([Ru(bpy)(pynp)(CO)(CH₃CN)]²⁺) was also prepared by replacement reactions of the chlorido ligand in CH₃CN. Using these complexes, ligand-centered redox behavior was studied by electrochemical and spectroelectrochemical techniques. The molecular structures of pynp-containing complexes (two stereoisomers of [Ru(bpy)(pynp)(CO)Cl]PF₆ and [Ru(pynp)₂(CO)Cl]PF₆) were determined by X-ray structure analyses.     

Complexes of benzo-15-crown-5 with protonated primary amines and diamines

Three complexes of benzo-15-crown-5 (B15C5) with protonated primary amines [PhCH₂NH₃(B15C5)](ClO₄), [p-C₆H₄(CH₂NH₃)₂(B15C5)₂](ClO₄)₂, and [(CH₂)₄(NH₃)₂(B15C5)₂](SCN)₂ were isolated and studied in acetonitrile solutions by NMR, and in the solid state by X-ray crystallography. In all complexes, one B15C5 molecule was bound with each R-NH₃⁺ moiety with characteristic small separation of 1.84-1.86 Å between the nitrogen of the R-NH₃⁺ group and the O₅ mean plane of the crown residue. No sandwich-type complexes with a 1:2 R-NH₃⁺/B15C5 stoichiometry were observed. Binding affinities of B15C5 in acetonitrile were similar for all ammonium cations studied: K₁=550±10 M⁻¹ for [PhCH₂NH₃]⁺; K₁=1100±100 and K₂=400±30 M⁻¹ for [p-C₆H₄(CH₂NH₃)₂]²⁺; and K₁=1100±100 and K₂=300±30 M⁻¹ for [H₃N(CH₂)₄NH₃]²⁺. The complexation is primarily enthalpy-driven (ΔH°=−4.9±0.5 kcal/mol, ΔS°=−3.8±1.0 eu for PhCH₂NH₃⁺-B15C5), as determined by variable temperature ¹H NMR titrations.     

Challenges in modelling and optimisation of stability constants in the study of Cu-(TAPS)x-(OH)y system by polarography

This work describes the application of polarography, a technique scarcely used for modelling and optimisation of stability constants, in the study of copper complexes with [(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino]-1-propanesulfonic acid (TAPS). Direct current polarography (DCP), using low total copper ion and large total ligand to total copper concentration, enabled the full characterization of Cu-(TAPS)_x-(OH)_y system, whose complexation occurs in the pH range of copper hydrolysis and Cu(OH)₂ precipitation. Cu-(TAPS)_x-(OH)_y system was studied by DCP and glass electrode potentiometry (GEP) in aqueous solution at fixed total ligand to total metal concentrations ratios and varied pH values (25.0 °C; I = 0.1 M, KNO₃). The predicted model, as well as the overall stability constants values, are (as log β): CuL⁺ = 4.2, CuL₂ = 7.8, CuL₂(OH)⁻ = 13.9 and CuL₂(OH)₂²⁻ = 18.94. GEP only allowed confirming the stability constants for CuL⁺ and CuL₂ and was used to determine the pKa of TAPS, 8.342.Finally, a briefly comparative analysis between TAPS and other structural related buffers was done. Evaluation based on log β_CuL versus pKa revealed that TES, TRIS, TAPS and AMPSO coordinated via amino and hydroxymethylgroups forming a five-membered chelate ring. For BIS-TRIS and TAPSO, and possibly DIPSO, one or more five-membered chelate rings involving additional hydroxyl groups are also likely formed.     

Thermodynamic behavior of complexation process between dibenzo-18-crown-6 and K+, Ag+, NH 4 + , and Hg2+ cations in ethylacetate-dimethylformamide binary media

The complexation reactions between K⁺, Ag⁺, NH₄⁺, and Hg²⁺ cations and the macrocyclic ligand, dibenzo-18-crown-6 (DB18C6), were studied in ethylacetate (EtOAc)-dimethylformamide (DMF) binary mixtures at different temperatures using the conductometric method. The conductance data show that the stochiometry of all the complexes is 1:1. A non-linear behavior was observed for the variation of log K _f of the complexes versus the composition of binary mixed solvents, which was discussed in terms of heteroselective solvation and solvent-solvent interactions in binary solutions. It was found that the stability order of the complexes changes with changing the composition of the mixed solvents. The sequence of stabilities for the K⁺, Ag⁺, NH₄⁺, and Hg²⁺ complexes with DB18C6 in EtOAc-DMF binary solutions (mol. % DMF 25.0) and (mol. % DMF 50.0) at 25°C is (DB18C6-Ag)⁺ > (DB18C6-K)⁺ > (DB18C6-Hg)²⁺ > (DB18C6-NH₄)⁺, but in the cases of pure DMF and a binary solution of EtOAc-DMF (mol. % DMF 75.0) is (DB18C6-K)⁺ > (DB18C6-Hg)²⁺ > (DB18C6-Ag)⁺ ≈ (DB18C6-NH₄)⁺. The values of thermodynamic quantities (ΔH _c ^o, ΔS _c ^o) for these complexation reactions have been determined from the temperature dependence of the stability constants, and the results show that the thermodynamics of the complexation reactions is affected by the nature and composition of the mixed solvents and, in all cases, positive values of ΔS _c ^o characterize the formation of these complexes. In addition, the experimental results show that the values of entropies for the complexation reactions between K⁺, Ag⁺, NH₄⁺, and Hg²⁺ cations and DB18C6 in EtOAc-DMF binary solutions do not change monotonically with the solvent composition. The text was submitted by the authors in English.     

Preparation of porous PMMA/Na–montmorillonite cation-exchange membranes for cationic dye adsorption

Porous PMMA/Na⁺–montmorillonite (MMT) cation-exchange membranes were successfully prepared by entrapment method in this study. One approach (simple mixing) was to mix commercial PMMA polymer with Na⁺–MMT clays in solvent for membrane preparation (Membrane A). The other approach (emulsion polymerization) was to synthesize the PMMA/Na⁺–MMT polymer composite via emulsion polymerization first, followed by membrane casting (Membrane B for Kunipia F clays and Membrane C for PK-802 clays). Membrane morphology and properties were characterized. The thermogravimetric analysis (TGA) verified the near complete incorporation of feed Na⁺–MMT clays in the PMMA/Na⁺–MMT composite membranes, while X-ray diffractograms (WXRD) exhibited the slightly enlarged interlayer spacing of Na⁺–MMT. The range of cation-exchange capacity (CEC) was 9–32 μequiv./47 mm disc. For batch cationic dye adsorption, the best performance was achieved by Membrane B with feed Na⁺–MMT/MMA (M/P) ratio (w/w) = 0.5 and Membrane C with feed M/P = 0.6, where about 95% Methyl violet adsorption was attained in 2 h. The optimal desorption solution was 1 M KSCN in 80% methanol and its related dye desorption efficiency was 92%. In the flow process using one piece of 47 mm disc of Membrane B (M/P = 0.5), dye solution was recirculated for 6 h and ≥85% dye could be removed. Higher than 94% of dye was desorbed at 1 or 4 mL/min, and the membrane regenerability was proved by successfully performing three consecutive cycles.     

The structures of (phenylato)(N-2-thiophenecarboxamido-meso-tetraphenylporphyrinato)mercury(II) and bisphenylmercury(II) complex of 21-(4-tert-butyl-benzenesulfonamido)-5,10,15,20-tetraphenylporphyrin

The reaction of PhHgOAc with N-NHCO-2-C₄H₃S-Htpp (5) and N-p-HNSO2C6H4^tBu-Htpp (4) gave a mercury (II) complex of (phenylato) (N-2-thiophenecarboxamido-meso-tetra phenylporphyrinato)mercury(II) 1.5 methylene chloride solvate [HgPh(N-NHCO-2-C₄H₃S-tpp) · CH₂Cl₂ · 0.5C₆H₁₄;  6 · CH₂Cl₂ · 0.5C₆H₁₄] and a bismercury complex of bisphenylmercury(II) complex of 21-(4-tert-butyl-benzenesulfonamido)-5,10,15,20-tetraphenylporphyrin, [(HgPh)2(N-p-NSO₂C₆H₄^tBu-tpp); 7], respectively. The crystal structures of 6 · CH₂Cl₂ · 0.5C₆H₁₄ and 7 were determined. The coordination sphere around Hg(1) in 6 · CH₂Cl₂ · 0.5C₆H₁₄ and Hg(2) in 7 is a sitting-atop derivative with a seesaw geometry, whereas for the Hg(1) in 7, it is a linear coordination geometry. Both Hg(1) in 6 · CH₂Cl₂ · 0.5C₆H₁₄ and Hg(2) in 7 acquire 4-coordination with four strong bonds [Hg(1)–N(1) = 2.586(3) Å, Hg(1)–N(2) = 2.118(3) Å, Hg(1)–N(3) = 2.625(3) Å, and Hg(1)–C(50) = 2.049(4) Å for 6 · CH₂Cl₂ · 0.5C₆H₁₄; Hg(2)–N(1) = 2.566(6) Å, Hg(2)–N(2) = 2.155(6) Å, Hg(2)–N() = 2.583(6) Å, and Hg(2)–C(61) = 2.064(7) Å for 7]. The plane of the three pyrrole nitrogen atoms [i.e., N(1)–N(3)] strongly bonded to Hg(1) in 6 · CH₂Cl₂ · 0.5C₆H₁₄ and to Hg(2) in 7 is adopted as a reference plane 3N. For the Hg²⁺ complex in 6 · CH₂Cl₂ · 0.5C₆H₁₄, the pyrrole nitrogen bonded to the 2-thiophenecarboxamido ligand lies in a plane with a dihedral angle of 33.4° with respect to the 3N plane, but for the bismercury(II) complex in 7, the corresponding dihedral angle for the pyrrole nitrogen bonded to the NSO₂C₆H₄^tBu group is found to be 42.9°. In the former complex, Hg(1)²⁺ and N(5) are located on different sides at 1.47 and −1.29 Å from its 3N plane, and in the latter one, Hg(2)²⁺ and N(5) are also located on different sides at −1.49 and 1.36 Å form its 3N plane. The Hg(1)?Hg(2) distance in 7 is 3.622(6) Å. Hence, no metallophilic Hg(II)?Hg(II) interaction may be anticipated. NOE difference spectroscopy, HMQC and HMBC were employed to unambiguous assignment for the ¹H and ¹³C NMR resonances of 6 · CH₂Cl₂ ·  0.5C₆H₁₄ in CD₂Cl₂ and 7 in CDCl₃ at 20 °C. The ¹⁹⁹Hg chemical shift δ for a 0.05 M solution of 7 in CDCl₃ solution is observed at −1074 ppm for Hg(2) nucleus with a coordination number of four and at −1191 ppm for Hg(1) nucleus with a coordination number of two. The former resonance is consistent with that chemical shift for a 0.01 M solution of 6 in CD₂Cl₂ having observed at −1108 ppm for Hg(1) nucleus with a coordination number of four.