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The H+(aq) ion in ionized strong aqueous acids is an unexpectedly unique H13O6+ entity, unlike those in gas phase H+(H2O)n clusters or typical crystalline acid hydrates. IR spectroscopy indicates that the core structure has neither C3v H3O+ Eigen-like nor typical H5O2+ Zundel-like character. Rather, extensive delocalization of the positive charge leads to a H13O6+ ion having an unexpectedly long central O O separation of ~2.57 A ° and four conjugated O O separations of ~2.7 Å. These dimensions are in conflict with the shorter O/O separations found in structures calculated by theory. Ultrafast dynamic properties of the five H atoms involved in these H-bonds lead to a substantial collapse of normal IR vibrations and the appearance of a continuous broad absorption (cba) across the entire IR spectrum. This cba is distinguishable from the broad IR bands associated with typical low-barrier H-bonds. The solvation shell outside of the H13O6+ ion defines the boundary of positive charge delocalization. At low acid concentrations, the H13O6+ ion is a constituent part of an ion pair that has contact with the first hydration shell of the conjugate base anion. At higher concentrations, or with weaker acids, one or two H2O molecules of H13O6+ cation are shared with the hydration shell of the anion. Even the strongest acids show evidence of ion pairing. © The Royal Society of Chemistry 2011.

The synthetic and structural chemistry of catalytically useful trialkylsilylium salts with weakly coordinating carborane anions, R 3Si(CHB11X11), has been extended to the heavier group 14 elements. Et3Ge(CHB11H5Br 5) was prepared from Et3GeH and trityl CHB 11H5Br6-. Its X-ray crystal structure shows ion-like character very similar to its Si congener. The heavier element analogues, Et3E(CHB11H5Br6) (E = Sn, Pb), were prepared by chloride ion abstraction from Et3SnCl and Et3PbCl, respectively, using Et3Si(CHB 11H5Br6). Their crystal structures differ from those of the four-coordinate lighter elements by adopting five-coordinate trigonal-bipyramidal stereochemistries, reflecting the periodic table transition of these elements from semi-metals to metals. The carborane anions are weak, bridging, axial ligands connecting trigonal Et3E+ cation-like moieties in polymeric chain structures. When the less coordinating CHB11Cl11- anion is used, excess germane competes with the carborane anion for coordination to Ge and a salt of the new hydride-bridged cation [Et3Ge-H-GeEt3]+ can be isolated. It has a distinctive αGeHGe IR band at ca. 1740 cm-1 analogous to the 1875 cm-1 band of the [Et3Si-H-Si-Et 3]+ cation. Comparable chemistry is not observed for the Sn and Pb congeners. © 2010 American Chemical Society.

The long-standing problem of understanding the nature of the "excess proton" in acidified water is simplified by studying the proton in methanol. The 3D network of hydrogen bonds in H(aq)+ is reduced to a ID problem. Infrared spectroscopic characterization of linear chain methanol proton solvates in H(CH3OH)n+ for n = 2-8 provides insight into some of the puzzling IR spectral features associated with O-H-O vibrations. These include the virtual disappearance of otherwise strong bands from H-bonded methanol molecules adjacent to symmetrical O-H +-O groups. The data indicate that a chain of up to four O-H⋯-O bonds either side of this group can act as an electrical wire to separate positive charge. This suggests a refinement of the Grotthuss proton-hopping mechanism for explaining the anomalously high mobility of H + in Hbonded media. © 2008 Wiley-VCH Verlag GmbH & Cu. KGaA.

Silylium ion-like reagents, R3Si δ+(carboraneδ-), are successful where silver salts fail in abstracting chloride ion from IrCl(CO)(PPh3) 2 in arene solvents. Replacement of chloride by a very weakly coordinating carborane anion such as CHB11H5Cl 6- promotes unusually facile oxidative addition of chlprobenzene, giving the coordinatively unsaturated IrCl(CO)(C 6H5)(PPh3)2]+ cation. Other arene solvents promote disproportionation with loss of aphosphme ligand to give labile Ir(I) cations of the type [Ir(arene)(CO)(PPh3)] +, having three latent vacant coordination sites. © 2008 American Chemical Society.

The boron subphthalocyanine cation, B(SubPc)+, has been prepared as a salt of a weakly coordinating carborane anion, CHB11Me 5Br6-, by a metathesis reaction of Et 3Si(CHB11Me5Br6) with B(SubPc)Cl. The separation of the cation and anion in the X-ray structure indicates coordinative unsaturation at the boron center, and this is corroborated by DFT calculations. A strongly Lewis acidic nature for the B(SubPc)+ cation is indicated by its hydrolysis to an unusual product, the di-meso-N-protonated -oxo dimer, [H(SubPc)B-O-B(SubPc)H]2+. ©2006 Wiley Periodicals, Inc.

Tetra(pentafluorophenyl)porphyrin (H2TPFPP) has been cocrystallized with C60 from arene solvents to give H 2TPFPP·C60, 1, H2TPFPP·C 60·8Benzene, 3, and 3H2TPFPP·2C 60·6Toluene, 4. Their X-ray structures have been determined to identify the supramolecular interactions that lead to tape, sheet, and prismatic packing motifs. In addition to close fullerene-porphyrin π-π interactions, attractive C-F⋯H-C interactions are important in connecting the C6F5 groups of one porphyrin to the pyrrole positions of a neighbor. This interaction is also seen in the structure of the free-base porphyrin H2TPFPP·3p-Xylene, 2. © 2006 American Chemical Society.

The nature of solvated acids in benzene and chlorinated hydrocarbon solvents is sensitively revealed by IR spectroscopy. Two similarly strong, structurally related acids, triflic acid (CF 3SO 3H) and the N-H acid bis-(trifluoromethylsulfonyl) imide ((CF 3SO 2) 2NH), behave quite differently toward water in. these media. Triflic acid protonates water at the one-equivalent level to give the hydronium ion, H 3O +. By contrast, bis(trifluoromethylsulfonyl) imide forms a simple hydrate, (CF 3SO 2) 2NH-OH 2, even with water at the two-equivalent level. The difference arises from the differing abilities of the conjugate base anions to engage in H-bonding and ion pairing. It illustrates how acidity in low-dielectric media is critically dependent on the nature of the conjugate base anion. νO-H and νN-H stretching frequencies indicate that the H-bonding acceptor ability for solvents toward acidic protons increases in the order carbon tetrachloride < benzene ∼ 1, 2-dichoroethane < water. With benzene, a marked tendency for acidic protons to H-bond to the π-face of the arene ring is noted and an IR signature of this solvation mode is observed.

The vas(COC) IR spectral signatures of polyethers in H-bonded hydronium ion complexes have been established in studies of H3O+ and H5O2+ complexes with 15-crown-5, 18-crown-6, dibenzo-18-crown-6, and their open chain poly(ethylene glycol) analogues in 1,2-dichoroethane solutions. When experiment meets theory in the structure of the H3O+·18-crown-6 complex, there is disagreement. While DFT calculations at the BLYP/II′// BLYP/6-31G* level indicate a C3v structure with three normal, static linear H bonds to alternate O atoms of the crown ether, IR spectroscopy in the v(C-O-C) region indicates that all six O atoms are equivalent. A new type of low-barrier H-bonding involving rotational mobility of H3O+ is proposed to rationalize the experimental observations.

Electron spin transient nutation (ESTN) experiments show that the spin multiplicity of the ground state of C603- in frozen solution is a doublet with S = 1/2. In purified samples, there is no evidence for excited states or other species with higher multiplicity. In the anions of C120On- (n = 2, 3, 4), where the CW EPR experiments have shown that a mixture of species is present, ESTN experiments confirm that a doublet with S = 1/2 is associated with the 3- anion and triplets with S = 1 are associated with the 2- and 4- anions. A weak nutation peak attributable to ms = -1/2 ↔ 1/2 transitions within a quartet state may arise from association of anions with spins of 1/2 and 1 in solute aggregates.

Time-resolved EPR spectra were observed by means of the transient EPR technique for two kinds of fullerene dimers C120 and C120O in the lowest excited triplet (T1) states and compared with those of mono-adducts of fullerene (C60). It was found that zero-field splitting (zfs) parameters of both dimers are nearly the same as those of the monomers, indicating that the excitation is almost completely localized at one of the two fullerene units in the T1 state. © 2002 Elsevier Science B.V. All rights reserved.

The action of heat and pressure on a co-crystallate of C60 and a calixarene, where the fullerenes are pre-organized in separated linear columns, gives a linear [2 + 2] addition polymer of (C60)(n) without crosslinking.

A new class of low-melting N,N'-dialkylimidazolium salts has been prepared with carborane counterions, some of the most inert and least nucleophilic anions presently known. The cations and anions have been systematically varied with combinations of 1-ethyl-3-methyl-(EMIM+), 1-octyl-3-methyl-(OMIM+), 1-ethyl-2,3-dimethyl-(EDMIM+), and 1-butyl-2,3-dimethyl-(BDMIM+) imidazolium cations and CB11H12-, CB11H6Cl6-, and CB11H6Br6- carborane anions to elucidate the factors which affect their melting points. From trends in melting points, which range from 156 °C down to 45 °C, it is clear that the alkylation pattern on the imidazolium cation is the main determinant of melting point and that packing inefficiency of the cation is the intrinsic cause of low melting points. C-Alkylation of the anion can also contribute to low melting points by the introduction of a further packing inefficiency. Nine of the thirteen salts have been the subject of X-ray crystal structural determination. Notably, crystallographic disorder of the cation is observed in all but one of these salts. It is the most direct evidence to date that packing inefficiency is the major reason unsymmetrical N,N'-dialkylimidazolium salts can be liquids at room temperature.

The long-debated origin of the narrow line-width signal in the EPR spectrum of C60- is shown to be C120O-, arising from unavoidable C120O impurity in air-exposed samples of C60.

A new superacid, H(CB11H6X6) (where X = chlorine or bromine), whose conjugate base is the exceptionally inert CB11H6X6- carborane anion, separates Bronsted acidity from oxidizing capacity and anion nucleophilicity in a manner not previously achieved. Reaction of this superacid with C60 gives HC60+ as a stable ion in solution and in the solid state. In a separate experiment, an oxidant was developed such that the long-sought C60.+ ion can be synthesized in solution. The preparation of these two fullerene carbocations is a notable departure from the prevalent chemistry of C60, which is dominated by the formation of anions or the addition of nucleophiles. The H(CB11H6X6) superacid overcomes the major limitations of presently known superacids and has potentially wide application.

Contrary to expectations based on the spectrochemical series, H2O is found to be a significantly weaker field ligand than OH- in the magnetochemical series ranking of ligand field strengths based on the spin states of iron(III) tetraphenylporphyrin complexes. The preparation and characterization of the [Fe(H2O)(TPP)]+ ion and the spectroscopic identification of Fe(OH)(TPP) have made this assessment possible. These two species were previously thought to be unattainable because of the facile formation of the well-known μ-oxo dimer, (TPP)Fe-O-Fe(TPP). However, the special characteristics of single equivalents of water under high acidity, relevant to metalloenzyme active sites and superacidity, make them accessible in benzene solution. Their 1H NMR β-pyrrole chemical shifts at -43 and +82 ppm indicate admixed-intermediate S = 3/2, 5/2 and high S = 5/2 spin states for the aqua and hydroxo species, respectively. The X-ray crystal structure of the aqua complex has been determined for [Fe(H2O)(TPP)] [CB11H6Cl6] and is consistent with the high degree of S = 3/2 character indicated by the NMR measurement, Mossbauer spectroscopy (ΔE(q) = 3.24 mm·s-1), and magnetic susceptibility (μ(eff) = 4.1 μ(B)). The anhydrous precursor to these species is the 'nearly bare' iron(III) porphyrin complex Fe(CB11H6Br6)(TPP). Judged by its magnetic parameters (δ(pyrrole) = -62 ppm, ΔE(q) = 3.68 mm·s-1, μ(eff) = 4.0 μ(B)) it attains the long sought essentially 'pure' S = 3/2 spin state. The magnetochemical ranking of ligand field strengths in five-coordinate high-spin and admixed-intermediate-spin iron(III) porphyrins is useful because it more closely reflects the intuitive field strengths of crystal field theory than does the usual spectrochemical ranking, which is controlled largely by π effects in octahedral low-spin d(π)6 complexes.

Naturally assembling cocrystallates of C60 and C70 fullerenes with tetraphenylporphyrins (H2TPP · C60 · 3 toluene, 1; H2T(3,5-dibutyl)PP · C60, 2; H2T(3,5-dimethyl)PP · 1.5C60 · 2 toluene, 3; H2T(piv)PP · C60, 4; H2T(3,5-dimethyl)PP · C70 · 4 toluene, 5; ZnTPP · C70, 6; NiT(4-methyl)PP · 2C70 · 2 toluene, 7) show unusually short porphyrin/fullerene contacts (2.7-3.0 Å) compared with typical π-π interactions (3.0-3.5 Å). In the C60 structures, an electron-rich, 6:6 ring juncture, C-C bond lies over the center of the porphyrin ring. In the C70 structures, the ellipsoidal fullerene makes porphyrin contact at its equator rather than its poles; a carbon atom from three fused six-membered rings lies closest to the center of the porphyrin. These structures provide an explanation for the manner in which tetraphenylporphyrin-appended silica stationary phases effect the chromatographic separation of fullerenes. The interaction of the curved π surface of a fullerene with the planar π surface of a porphyrin, without the need for matching convex with concave surfaces, represents a new recognition element in supramolecular chemistry. NMR measurements show that this interaction persists in toluene solution, suggesting a simple way to assemble van der Waals complexes of donor-acceptor chromophores.

Benzene, toluene, p-xylene, and [60]fullerene are shown to be weak ligands to a hard metal such as iron(III) in Fe(TPP)+ cation (TPP = tetraphenylporphyrinate). X-ray crystal structures of [Fe(TPP)(C6H6)][CB11H6Br6] · 3.5C6H6 (1), [Fe(TPP)(C7H8)][CB11H6Cl6] · 2C7H8 (2), [Fe(TPP)(C8H10)][Ag(CB11H6Br6)2] · arene (3), and [Fe(TPP)(C60)][F20-BPh4] · 2.5dichlorobenzene (4) show distinctively short Fe · · · C contacts, in the range 2.65-2.95 Å, which distinguish ligation from π-π cocrystallized solvation. Dihedral angles between the arene and metalloporphyrin planes are also diagnostic of ligand versus solvate roles. The essential features of the arene coordination can be faithfully reproduced using density functional theory. In contrast to alkali metal cation/π-arene interactions, a component of the covalent bonding can be recognized. In a broader context, this study suggests that solvents such as benzene should always be viewed as potential ligands in the presence of coordinatively unsaturated cations. The common use in supramolecular chemistry of the term 'noncovalent' to describe entities with metal-ligand bonds is viewed as misleading.

Introduction: Diabetes screening traditionally occurs in primary care settings, but many who are at high risk face barriers to accessing care and therefore delays in diagnosis and treatment. These same high-risk patients do frequently visit emergency departments (ED) and, therefore, might benefit from screening at that time. Our objective in this study was to analyze one year of results from a multisite, ED-based diabetes screening program. Methods: We assessed the demographics of patients screened, identified differences in rates of newly diagnosed diabetes by clinical site, and the geographic distribution of high and low hemoglobin A1c (HbA1c) results. Results: We performed diabetes screening (HbA1c) among 4,211 ED patients 40–70 years old, with a body mass index ≥25, and no prior history of diabetes. Of these patients screened for diabetes, 9% had a HbA1c result consistent with undiagnosed diabetes, and nearly half of these patients had a HbA1c ≥9.0%. Rates of newly diagnosed diabetes were notably higher at EDs located in neighborhoods of lower socioeconomic status. Conclusion: Emergency department-based diabetes screening may be a practical and scalable solution to screen high-risk patients and reduce health disparities experienced in specific neighborhoods and demographic groups.

The proton NMR spectra of unligated ferrous porphyrins, proposed to exist in the intermediate S = 1 spin state, have been recorded and analyzed. The dominant dipolar shifts for the phenyl protons in tetraphenylporphinatoiron(II) result in a quantitative measure of the axial magnetic anisotropy, which, together with the average moment, yield μ⊥ = 4.9 μB and μ|| = 3.2 μB. The resultant contact shifts for pyrrole substituents reflect extensive π spin transfer, which originates solely from porphyrin → iron change transfer. The contact shift pattern indicates that dx2y2 is unoccupied, confirming the spin-triplet ground state. The large π contact shifts require unpaired spins in dxz, dyz, and strongly support the ground state configuration, (dxy)2(dzi)2(dxz, dyz)2, which has been previously shown to be the one favored by the average moment and Mössbauer data. © 1977, American Chemical Society. All rights reserved.

The khmer package is a freely available software library for working efficiently with fixed length DNA words, or k-mers. khmer provides implementations of a probabilistic k-mer counting data structure, a compressible De Bruijn graph representation, De Bruijn graph partitioning, and digital normalization. khmer is implemented in C++ and Python, and is freely available under the BSD license at https://github.com/dib-lab/khmer/.