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Alkaline high-level waste (HLW) generated as a result of years of nuclear weapons production has complicated composition and requires comprehensive treatment methods, which would allow concentratin...

Selectivity for An(iii) vs. Ln(iii) binding and extraction using dipicolinamide analogs containing the C[double bond, length as m-dash]O vs. C[double bond, length as m-dash]S groups was investigated in solution and the gas-phase, and by DFT calculations. The results show higher selectivity for complex formation and extraction for Am(iii) vs. Eu(iii) for the softer dithioamide vs. the diamide ligand, while in CH3CN the diamide binds more strongly than the thioamide to several Ln(iii), forming 1 : 1 complexes.

A fluorescent sensor for NH4+ based on 1,3,5-triethylbenzene shows remarkable binding and sensing selectivity for NH4+vs. K+. Fluorescence and NMR titrations reveal surprising differences in the sensing properties and binding constants of tris-(3,5-dimethyl)pyrazole 1vs. tris(3,5-diphenyl)pyrazole 2. The roles of ion pairing and solvation are revealed by X-ray and DFT studies.

The croconate dianion is a highly versatile ligand with two tautomeric forms making it useful for building large superstructures in the solid state. The single-crystal X-ray structures of Pb

An o-phenylenediamine-derived dithioamide L was found to sense Hg(II) in the UV–visible via Hg(II)-mediated cyclization leading to a new benzimidazole derivative (L′). Both L and L′ have been characterized by single-crystal X-ray crystallography. The structure of L reveals relatively strong intramolecular H-bonding interactions of N H...S type. The extended structure is consolidated by several classical hydrogen bonding interactions. For L′, analysis of the packing pattern reveals few non-classical H-bonding contacts. Spectroscopic studies by FT-IR, UV–Visible, 1H-and 13C NMR support the single-crystal X-ray crystallography results and confirm the formation of the new benzimidazole derivative. UV–Vis titrations suggest and NMR confirms that the cyclization reaction occurs via an initial formation of a Hg(II) complex, which is too transient to be fully characterized. As this reaction is Hg(II)-mediated, dithioamide L acts as a selective Hg(II) sensor as shown by UV–Visible titrations and a selectivity study against Pb(II), Cd(II), Ca(II), Zn(II), Ag(I), and Cr(III): For Hg(II), but not for other metals, a distinct color change from yellow to pink is observed with corresponding UV–Vis spectroscopic changes and an isosbestic point at 270 nm.

The problem of legacy alkaline high-level waste (HLW) both in the US and Russia, as a result of weapons production, has prompted studies of ligands for extraction of actinides, that could be possibly used in the future together with Cs extractants for combined HLW extraction processes. The tripodal trisulphonamide ligand 1,3,5-tris-(4-(iso-propyl)-phenylsulfamoylmethyl)benzene (4-iPr-tsa), which has pre-organised functional groups for An(III) binding was synthesised and studied for potential Sm(III) and Am(III) binding and extraction by theoretical (DFT) and experimental (extraction) methods (for Sm(III) only). Both theory and experiments suggest that even though this family of ligands shows promise for Ln(III) and An(III) binding with minima for complex formation, complexation is competing with hydrolysis, and extraction is only feasible in alkaline solutions, in the presence of high concentrations of nitrate ions. Nevertheless, up to 51.8% of Sm(III) was removed under optimal conditions (NaOH = 2 × 10−4 M, NaNO3 = 0.1 M, [Sm]init = 5 × 10−5 M). Quantum chemical calculations demonstrate that the extraction of Sm(III) and Am(III) from the aqueous phase in the form of [M·(H2O)4·(OH)2·(NO3)] to the organic phase in the form of [M·4-iPr-tsa·(H2O)3] is thermodynamically favourable. Theory also shows that Sm(III) is a reasonably good surrogate for Am(III), as the optimised structures of the Sm and Am complexes show remarkable similarities. Even though the ligand was designed with the goal of introducing favourable cation–arene interactions, along with the expected N-binding mode of the ligand in its deprotonated form, it was found that these cation–arene interactions are rather weak in this case, and coordination with O atoms of the sulphonamide, and external water molecules, is favoured instead.

Nitric oxide (NO) research in biomedicine has been hampered by the absence of a method that will allow quantitative measurement of NO in biological tissues with high sensitivity and selectivity, and with adequate spatial and temporal resolution. 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF-FM) is a NO sensitive fluorescence probe that has been used widely for qualitative assessment of cellular NO production. However, calibration of the fluorescent signal and quantification of NO concentration in cells and tissues using fluorescent probes, have provided significant challenge. In this study we utilize a combination of mathematical modeling and experimentation to elucidate the kinetics of NO/DAF-FM reaction in solution. Modeling and experiments suggest that the slope of fluorescent intensity (FI) can be related to NO concentration according to the equation: ddtFI=2αk(1)NO(2)O(2)DAF-FMkNO+DAF-FM where α is a proportionality coefficient that relates FI to unit concentration of activated DAF-FM, k(1) is the NO oxidation rate constant, and k was estimated to be 4.3±0.6. The FI slope exhibits saturation kinetics with DAF-FM concentration. Interestingly, the effective half-maximum constant (EC(50)) increases proportionally to NO concentration. This result is not in agreement with the proposition that N(2)O(3) is the NO oxidation byproduct that activates DAF-FM. Kinetic analysis suggests that the reactive intermediate should exhibit NO-dependent consumption and thus NO(2)() is a more likely candidate. The derived rate law can be used for the calibration of DAF-FM fluorescence and the quantification of NO concentration in biological tissues.

Nitrosation of thiols is thought to be mediated by dinitrogen trioxide (N 2 O 3 ) or by nitrogen dioxide radical ( NO 2 ). A kinetic study of glutathione (GSH) nitrosation by NO donors in aerated buffered solutions was undertaken. S -nitrosoglutathione (GSNO) formation was assessed spectrophotometrically and by chemiluminescence. The results suggest an increase in the rate of GSNO formation with an increase in GSH with a half-maximum constant EC 50 that depends on NO concentration. Our observed increase in EC 50 with NO concentration suggests a significant contribution of NO 2 -mediated nitrosation with the glutathiyl radical as an intermediate in the production of GSNO.

The o-phenylenediamine-derived disulfonamide ligands 1 and 2 complex and efficiently extract Pb(II) from water into 1,2-dichloroethane via ion-exchange, in combination with 2,2'-bipyridine (97.5% and 95.0%, respectively, for 1:1 ligand-to-Pb ratios). The corresponding Pb(II)-sulfonamido binary complexes of ligands 1 and 2 (3 and 4, respectively), and ternary complexes with 2,2'-bipyridine (5 and 6, respectively), were isolated and characterized. (1)H NMR spectra of the organic phases after extraction show the formation of ternary Pb-sulfonamido-bipy complexes. X-ray characterization of 3, 4, and the ternary complex 5 consistently demonstrates four primary coordination sites and a stereochemically active lone pair on Pb. The X-ray structure of 3 shows a pseudo trigonal bipyramidal configuration on Pb, with the lone pair occupying one of the equatorial sites, and the formation of an unusual "hemidirected" coordination polymer via axial S=O-Pb coordination. The same axial S=O-Pb coordination pattern with two DMSO molecules is observed in the structure of 4.[2(CH(3))(2)SO)], thus rationalizing the high solubility of the binary complexes in strongly coordinating solvents. In contrast, the X-ray structure of the ternary complex 5 reveals a distorted four-coordinate configuration with only weak S=O-Pb coordination leading to dimer formation, thus explaining its higher solubility in weakly coordinating solvents. FT-IR spectroscopy confirms the X-ray data, since the ligand nu(S)(=)(O) stretching frequencies shift to lower values in the binary Pb(II)-sulfonamido complexes and are again altered upon formation of the ternary Pb(II)-sulfonamido-bipy complexes, as would be expected for 2,2'-bipy complexation and hindered S=O-Pb coordination.

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH2Cl2). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(+)-cis-1-amino-2-indanol (2), and (R)-(+)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (n − Bu)4N+X− (X− = Cl−, NO3−, Br−, I−). Solutions of receptors and anions in CH2Cl2 were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes [M + X]−, (M = 1–3, X− = Cl−, NO3−, Br−, I−) were observed in negative mode APCI-MS along with the deprotonated receptors [M − H]−. Full ionization energy of the APCI corona pin (4.5 kV) was necessary for obtaining mass spectra with the best signal-to-noise ratios.

Lead is highly toxic and lead poisoning is a threat to human health, especially for children. Development of selective Pb chelates is necessary for its extraction, sensing and detoxification in environmental and biological systems.1 Numerous examples of coordination and extraction of Pb(II) by macrocycles have been reported.2–6 Ionizable chelates, which extract metals via ion exchange, offer potential advantages, such as versatility, synthetic ease, and favorable complexation-decomplexation kinetics. The recently reported disulfonamides, 1,7 2,7 and 3,1 are practical Pb(II) ion-exchange extractants that take advantage of the preference of Pb(II) in lower coordination numbers for irregular ‘hemidirected’ coordination geometries with a stereochemically active lone pair. These sulfonamides are very effective in Pb(II) extraction, even at micromolar levels, from water into 1,2-dichloroethane, and 3 in particular is very selective against Zn(II) and Cu(II).1,7 Electrospray ionization (ESI) is a soft ionization technique, and ESI-MS has been widely used to investigate non-covalent complexation, such as protein-protein interactions, enzyme-inhibitor complexes, nucleotides, drugs, and the formation of metal complexes.8,9 Although a number of cationic macrocycle–Pb complexes have been studied by ESI-MS,3–5,10 a method has not been established to investigate the neutral Pb complexes of ionizable chelators, such as disulfonamides, using MS. Recently, ESI-MS has been employed to measure stability constants for metal–crown ether complexes,11,12 to estimate relative stability of metal complexes,13,14 and to evaluate the binding selectivity of macrocycles.4 Therefore, ESI-MS could be potentially used to determine the stability of Pb–disulfonamide complexes, and a method based on ESI-MS could be eventually established for rapid screening of disulfonamide ligands for Pb complexation. Understanding the ionization mechanisms of these ligands and their Pb complexes involved in the ESI-MS processes is critical in order to achieve our long-term goal of developing MS methods for rapid detection of metal–complex formation. In this paper, we present an ESI-MS method for characterization of the disulfonamide ligands 1–4 and their Pb(II) complexes in both positive and negative modes.

The structure of N,N′-diphenyl-1,3-benzenedisulfonamide (1) was determined by single crystal X-ray diffraction. It crystallizes in P21/n with cell dimensions: a = 11.8390(6) A, b = 12.3950(10) A, c = 12.1184(10) A, β = 94.388(6)°, and V = 1773.1(2) A3. Its di-t-butyl derivative, N,N′-bis(4-t-butylphenyl)-1,3-benzenedisulfonamide (2), was prepared and structurally characterized as two solvated structures. Both crystallize in P\(\overline 1\) with cell dimensions: 2 ⋅ CF3CH2OH, a = 9.469(2) A, b = 10.0039(18) A, c = 16.385(3) A, α = 85.561(16)°, β = 83.035(18)°, γ = 72.459(16), and V = 1467.7(5) A3; 2 ⋅ ClCH2CH2Cl, a = 9.559(2) A, b = 9.8125(12) A, c = 17.100(6) A, α = 82.495(19)°, β = 83.47(2)°, γ = 70.100(15), and V = 1491.1(6) A3. The structures exhibit hydrogen-bonding, and are evaluated in terms of preorganization for anion binding.

Dipyrimidylamine (dipm) and tripyrimidylamine (tripm) are reported. A bidentate tripm ruthenium complex, [RuCl(η 6 - p -cymene)(κ 2 -tripm)]SbF 6 , is synthesized and structurally characterized. The presence of an intramolecular CH⋯N hydrogen bond is proposed between the cymene CH and a ring nitrogen in an uncoordinated pyrimidine ring. IR data on [Mo(CO) 4 (dipm)] suggest that the Tolman electronic parameter of the dipm ligand is similar to that of 2×PPh 3 . ML bonding may be weaker for pyrimidine versus pyridine because κ 2 -tripm complexation is apparently more favorable relative to the κ 3 -form than is the case for tripyridylamine.

We report here the synthesis of the new hydride complexes (C5H4CH(CH2CH2)2NMe)- RuH(PPh3)2 (1) and [(C5H4CH(CH2CH2)2NHMe)-RuH(PPh3)2](BF4) (2), the X-ray crystal structures of 1 and 2, and an unprecedented observation of extremely short relaxation times in a monohydride complex as well as in the reaction of CpRuH(PPh3)2 with a variety of acidic proton donors. The relaxation is much faster than expected for a dipole-dipole process involving the two dihydrogen-bonded protons, but no origin for the effect could be suggested.

Hydrogen bonding (Re–H···H–N) is estimated in solution between ReH5(PPh3)2L (L=pyridine, 4-picoline, 4-dimethylaminopyridine, and 4-carbomethoxypyridine), as hydrogen bond acceptor, and indole, as hydrogen bond donor. Re–H···base hydrogen bonding between [Re(PPh3)2(MeCN)4H][BF4]2 as hydrogen bond donor and various amines as hydrogen bond acceptors is much weaker. The binding strengths are estimated by UV-VIS spectroscopy.

The disulfonamide receptor 1 catalyzes imine formation from aldehyde and amine, apparently by binding the transition state for the rate-determining nucleophilic attack of amine on the aldehyde.

The (bis)dansylated sulfonamide 1,2-C6H4(NHSO2C10H6-5-N(CH3)2)2 (1) extracted Pb(II) selectively from water into 1,2-dichloroethane via an ion-exchange mechanism and showed fluorescence quenching upon Pb(II) extraction. The distribution ratios for metal extraction (determined by ICP-MS) for Pb(II) were 133-1410 times higher than those for other metal cations [Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)] under identical conditions. Fluorescence quenching was observed upon Pb(II) extraction, which was dependent on Pb(II) concentration. The monodansylated control, C6H5NHSO2C10H6-5-N(CH3)2 (2), showed neither extraction nor quenching, indicating that the fluorescence effects are a direct result of Pb coordination to 1. The observed selectivity for Pb(II) is ascribed to the formation of a low-coordinate binary Pb(II)-Sulfonamido complex in the organic phase.

The disulfonamide ligands 1,2-C(6)H(4)(NH(2)SO(2)C(6)H(5))(2) (1) and 1,2-C(6)H(4)(NH(2)SO(2)C(6)H(4)-p-Bu(t))(2) (2), which are readily available in good yields from o-phenylenediamine and the corresponding sulfonyl chlorides, efficiently extract Pb(II) from water into 1,2-dichloroethane when used in synergistic combinations with 2,2'-bipyridine via an ion-exchange mechanism. The extraction was shown to proceed via the formation of a ternary Pb-sulfamido-2,2'-bipyridine complex. The X-ray crystal structure of the binary Pb-sulfamido complex 3 shows a coordination polymer with a stereochemically active lone pair on Pb formed by S=O-Pb axial coordination.

Extraction of alkali metal salts by designed cation hosts, such as crown ethers 1 and calixarenes,2 has been widely investigated in recent years, as driven, to an extent, by the importance of separations of certain cationic contaminants such as Cs+ and Sr2+ in nuclear-fuel reprocessing and waste remediation. 3 New cation hosts used as extractants for these and other metals have reached impressive levels of selectivity for such demanding “needle-in-the-haystack” applications. The success of neutral cation hosts used in ion-pair extraction systems stems in part from the practical advantage of stripping extracted salts with water, resulting in processes that yield a pure salt product stream with little secondary waste. Examples of such practical ion-pair extraction applications include processes for nuclear-waste treatment that produce aqueous streams of relatively pure cesium nitrate2h or sodium pertechnetate,4 suitable for vitrification and geologic disposal. These processes employ calix-crown and crown ether extractants, such as those shown in Figure 1 for cesium. Although ion-pair extraction involves anion co-extraction, ligand design has focused primarily on the design of the cation host, typically with little or no attention to accommodating the anion.

When complexed by tetrabenzo-24-crown-8, the cesium ion can accommodate unprecedented ligation. The structures of the following complexes are presented. [Cs(tetrabenzo-24-crown-8)(eta 1-NCMe)2(eta 2-NCMe)][NO3] (1): triclinic P1, a = 12.0119(14) A, b = 13.3680(15) A, c = 13.7859(12) A, alpha = 89.124(8) degrees, beta = 66.928(9) degrees, gamma = 71.536(10) degrees, V = 1916.7(4) A3, Z = 2. [Cs(tetrabenzo-24-crown-8)(eta 1-NCMe)2(eta 2-CH2Cl2)][NO3] (2): triclinic, P1, a = 12.295(3) A, b = 13.295(3) A, c = 13.782(3) A, alpha = 89.105(17) degrees, beta = 66.096(18) degrees, gamma = 71.980(19) degrees, V = 1929.5(8) A3, Z = 2. These structures are the first reported examples of linear eta 2-acetonitrile coordination to any metal ion and the first structures illustrating eta 2-acetonitrile and dichloromethane ligation to an alkali metal ion. Possible steric and electronic origins of these unusual metal-ligand interactions are discussed.

A calix-crown/disulfonamide dual-host combination in 1,2-dichloroethane exhibits markedly enhanced ion-pair extraction of caesium salts, with the observed synergism following an anti-Hofmeister order.

The diamides and disulfonamides m-C(6)H(4)(CONHAr)(2) (Ar = Ph, 1; p-n-BuC(6)H(4), 2, 2,4,6-Me(3)C(6)H(2), 3), m-C(6)H(4)(SO(2)NHPh)(2), 4, and 2,6-C(6)H(3)N(CONHPh)(2), 5, readily synthesized on a multigram scale, bind strongly to halides and acetate in organic solvents with K(a)'s as high as 6.1 x 10(4) (NMR spectroscopy). The binding stoichiometry is 1:1 in solution for all cases except for the 4.F(-) and 4.OAc(-) complexes, where both 1:1 and 1:2 binding stoichiometries were found. The association constants in CD(2)Cl(2) ((1)H NMR) follow the trend Cl(-)Br(-)I(-) for all the receptors. F(-) and OAc(-) binding may be stronger or weaker than Cl(-) depending on the nature of the receptor. The presence of the pyridine nitrogen in 5 and of the more rigid amide in 1-3 and 5 vs the less rigid sulfonamide structure in 4 increases selectivity for smaller anions. The enthalpy and entropy of formation for 2.Cl(-) were DeltaH = -31 kJ/mol; DeltaS = -23 J/(mol.K) (VT-NMR). The X-ray structure of [PPh(4)](2)[1.Br][Br].CH(2)Cl(2), shows 1:1 complexation of Br(-) via two N-H.Br(-) hydrogen bonds and a syn-syn nonplanar binding conformation for 1. Solution hydrogen bonding was confirmed by FT-IR and NMR spectroscopy. The receptor conformation changes on complexation. Trends in structure/binding relationships show receptor flexibility is an important factor in anion recognition.

New ferrocenylamine derivatives 1,3-C6H4(CONHFc)2 (3), 1,3-C6H4(SO2NHFc)2 (4), and 1,3-C6H4(CONHFc)(COOEt) (5) (Fc = ferrocenyl), readily synthesized from FcNH2 and the appropriate acid dichlorides, bind chloride 1:1 as shown by 1H NMR, FT-IR, and cyclic voltammetry. NMR titrations gave association constants as high as 9.5 × 103 (for 4·Cl-). Cyclic voltammetry of 4·Cl- vs 4 shows a 20 mV negative shift for the ferrocene wave, indicating Cl- binding. An improved synthesis of FcNH2 is reported.

A systematic study of a dual-host system exhibiting pairwise anion/cation separations has been performed for CsNO3 extraction. Tripodal triamides 1-4 and 9 derived from condensation of hexanoic (for 1), octanoic (for 2), decanoic (for 3), lauric (for 4), and p-tert-butylbenzoic (for 9) acid with tris(2-aminoethyl)amine (tren) were used together with tetrabenzo-24-crown-8, a well-known Cs+ cation receptor. By using 5 mM crown ether in the organic phase and 10 mM CsNO3 with 0.1 mM HNO3 in the aqueous phase, tripods 1, 2, and 9 enhance CsNO3 extraction by factors of 2.4, 1.7, and 4.4, respectively (for 50 mM amide concentration), while the corresponding monoamide controls 5-8 derived from n-propylamine (5, 6) or N,N'-dimethylethylenediamine (7, 8) and hexanoic (5, 7) or octanoic (6, 8) acid derivatives gave no significant enhancement under the same conditions. This behavior may be ascribed to nitrate complexation by the triamides, which lowers the overall thermodynamic barrier for the salt transfer to the organic phase. The nitrate binding was confirmed by 1H NMR titration of receptor solutions, using tetrabutylammonium nitrate. Association constants for the formation of the anion-nitrate complexes were found to vary between 33 and 52 M-1 for the more soluble triamides. The synergistic effects for CsNO3 extraction are in reasonable agreement with the values predicted theoretically from the measured association constants. Electrospray ionization mass spectrometry confirmed the predominant formation of 1:1 tripod-nitrate complexes. Monoamide controls gave no evidence of anion complexation.

The N atoms of the title compound, C18H16N2O4S2, are not preorganized for metal cation binding. The N—H groups form hydrogen bonds with symmetry-equivalent sulfonamide groups.

The readily available benzene-1,3,5-tricarboxamide 1 enhances CsNO3 extraction by tetrabenzo-24-crown-8 via hydrogen bonding to the nitrate anion, as demonstrated by NMR and electrospray ionization mass spectrometry.

Human arsenic metabolism produces a number of species with varying toxicities; the presence of some has been identified while the existence of others has been postulated through indirect evidence. Speciation methods for the analysis of arsenite (AsIII), monomethylarsonous acid (MMAIII), dimethylarsinous acid (DMAIII), arsenate (AsV), monomethylarsonic acid (MMAV), dimethylarsinic acid (DMAV), arsino-glutathione (As(GS)3), monomethylarsino-glutathione (MMA(GS)2) and dimethylarsino-glutathione (DMA(GS)) were developed in this study through the use of cation exchange and reverse phase chromatography in a complementary manner. Electrospray ionization mass spectrometry (ESI-MS) was used for molecular identification of the arsenicals while inductively coupled plasma mass spectrometry (ICP-MS) was employed for quantitation purposes. Validation of the developed methods against each other for the quantitation of trivalent and pentavalent arsenicals was performed. The effect of reduced glutathione (GSH) concentration on the formation of arsenic-glutathione (As-GSH) complexes was studied. In the presence of glutathione, the occurrence of chromatographic artifacts on the cation exchange column was observed. The stability of trivalent arsenicals and As-GSH complexes was studied at various pH conditions. The results shed light on the importance of sample preparation, storage and proper choice of analytical column for the accurate identification of the As species. Reinvestigation of some of the previously reported As speciation studies of glutathione-rich biological samples needs to be performed for the verification of occurrence of As-GSH complexes and DMAIII.

The disulfonamide receptor 1 catalyzes imine formation from aldehyde and amine, apparently by binding the transition state for the rate-determining nucleophilic attack of amine on the aldehyde.