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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.

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.

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 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 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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.