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Time-resolved electron paramagnetic resonance spectroscopy, transient absorption, and phosphorescence spectroscopy were used to investigate the spin polarization of a nitroxide free radical induced by interaction with singlet oxygen ((1)O2). The latter was generated by photolysis of endoperoxides of two anthracene derivatives. Although both anthracene endoperoxides are structurally similar, opposite spin polarization of the nitroxide was observed. Photolysis of one endoperoxide leads to absorptive nitroxide spin polarization due to interaction with the generated (1)O2. Photolysis of the other endoperoxide generated emissive nitroxide spin polarization, probably due to interaction of the endoperoxide triplet states with nitroxides.

Relaxation rates of endo-H2O in H2O@Open-C60 in the presence of a nitroxide radical and of their nitroxide derivatives have been measured and are compared with effects for endo-H2 in similar cages. T1 relaxation enhancement of the endo-H2O and H2 induced by either intra- or intermolecular interaction is relatively insensitive to the presence of a cage opening. Enhancement of intermolecular relaxation is observed, however, when the cage opening has an OH group.

We present a solid-state NMR study of H2 molecules confined inside the cavity of C70 fullerene cages over a wide range of temperatures (300 K to 4 K). The proton NMR spectra are consistent with a model in which the dipole-dipole coupling between the ortho-H2 protons is averaged over the rotational/translational states of the confined quantum rotor, with an additional chemical shift anisotropy δ(H)(CSA)=10.1 ppm induced by the carbon cage. The magnitude of the chemical shift anisotropy is consistent with DFT estimates of the chemical shielding tensor field within the cage. The experimental NMR data indicate that the ground state of endohedral ortho-H2 in C70 is doubly degenerate and polarized transverse to the principal axis of the cage. The NMR spectra indicate significant magnetic alignment of the C70 long axes along the magnetic field, at temperatures below ~10 K.

An endofulleropyrrolidine, with H2 as a guest, has been reduced to a paramagnetic endofulleride radical anion. The magnetic interaction between the electron delocalized on the fullerene cage and the guest H2 has been probed by pulsed ENDOR. The experimental hyperfine couplings between the electron and the H2 guest were measured, and their values agree very well with DFT calculations. This agreement provides clear evidence of magnetic communication between the electron density of the fullerene host cage and H2 guest. The ortho-H2/para-H2 interconversion is revealed by temperature-dependent ENDOR measurements at low temperature. The conversion of the paramagnetic ortho-H2 to the diamagnetic para-H2 causes the ENDOR signal to decrease as the temperature is lowered due to the spin catalysis by the paramagnetic fullerene cage of the radical anion fulleride.

Inelastic neutron scattering, far-infrared spectroscopy, and cryogenic nuclear magnetic resonance are used to investigate the quantized rotation and ortho–para conversion of single water molecules trapped inside closed fullerene cages. The existence of metastable ortho -water molecules is demonstrated, and the interconversion of ortho -and para -water spin isomers is tracked in real time. Our investigation reveals that the ground state of encapsulated ortho water has a lifted degeneracy, associated with symmetry-breaking of the water environment.

The successful synthesis of H2O@C60 makes possible the study of magnetic interactions of an isolated water molecule in a geometrically well-defined hydrophobic environment. Comparisons are made between the T1 values of H2O@C60 and the previously studied H2@C60 and their nitroxide derivatives. The value of T1 is approximately six times longer for H2O@C60 than for H2@C60 at room temperature, is independent of solvent viscosity or polarity, and increases monotonically with decreasing temperature, implying that T1 is dominated by the spin-rotation interaction. Paramagnetic nitroxides, either attached covalently to the C60 cage or added to the medium, produce strikingly similar T1 enhancements for H2O@C60 and H2@C60 that are consistent with through-space interaction between the internal nuclear spins and the external electron spin. This indicates that it should be possible to apply to the endo-H2O molecule the same methodologies for manipulating the ortho and para spin isomers that have proven successful for H2@C60.

The photochemical interconversion of the two allotropes of the hydrogen molecule [para-H(2) (pH(2)) and ortho-H(2) (oH(2))] incarcerated inside the fullerene C(70) (pH(2)@C(70) and oH(2)@C(70), respectively) is reported. Photoexcitation of H(2)@C(70) generates a fullerene triplet state that serves as a spin catalyst for pH(2)/oH(2) conversion. This method provides a means of changing the pH(2)/oH(2) ratio inside C(70) by simply irradiating H(2)@C(70) at different temperatures, since the equilibrium ratio is temperature-dependent and the electronic triplet state of the fullerene produced by absorption of the photon serves as an "on-off" spin catalyst. However, under comparable conditions, no photolytic pH(2)/oH(2) interconversion was observed for H(2)@C(60), which was rationalized by the significantly shorter triplet lifetime of H(2)@C(60) relative to H(2)@C(70).

The complementary interface-sensitive methods of sum fre- quency generation (SFG) and surface tension have been used to investigate surfactants at the air/water interface. SFG yields information on the density and orientation of surfactants at the interface, whereas surface tension yields information on the surface excess of surfactants, which, however, is not their interfacial density. The rapid rise in the SFG signal to its maximum value at 1 mM, which remained essentially constant thereafter, was attributed to the formation of large surfactant domains. Above 1 mM, the domains, all of which have the same density, dominated the SFG signal. As a consequence, the SFG signalremainedessentiallyconstant.Thesurfaceexcesshadanequallyrapidrise to its maximum value at 1 mM, which remained constant until reaching a concentration of 3 mM, where it dropped to a zero value, indicating that a full surfactant monolayer had been formed. This coincides with the formation of bulk micelles, which is commonly referred to as the critical micelle concentration. The orientation of the surfactant carbonyl chromophore was obtained from polarization measure- ments of the SFG signal and showed a small change at and above a 1 mM concentration. The SFG results and the surface tension results, though inherently different, were found to be consistent with each other.

The ortho-H2→para-H2 conversion in a series of H2@C60 derivatives covalently linked to a nitroxide radical has been investigated. The resulting conversion rates are in good agreement with the Wigner’s theory, modified for intramolecular interaction of H2 with the paramagnet.

Summary Objective A mild moisturizing body wash with stearic acid, a key component of corneum lipids, and emollient soybean oil has been introduced in the market place. The objectives of this study are to determine the amount and the location of the stearic acid in the corneum after in vivo cleansing by the formulation. Method Clinical cleansing studies for one and five consecutive days were carried out with the formulation containing soybean oil or petroleum jelly (PJ). The free stearic acid in it was replaced by the fully deuterated variant. The amounts of stearic acid in 10 consecutive corneum tape strips were measured by liquid chromatograph‐mass spectroscopy. Separately, electron paramagnetic resonance (EPR) measurements were taken with a porcine skin after a wash by the soybean oil formulation with its free fatty acid replaced by its spin probe analogue, 5-doxyl stearic acid. Results Deuterated stearic acid was detected in all 10 consecutive layers of stratum corneum and the total amount after five washes with the soybean oil formulation was 0.33 lg ⁄cm 2 . The spin probe in cleanser-treated skin was incorporated in a partially ordered hydrophobic region similar to corneum lipids. The probe mobility increased in the temperature region where lipid disorder was expected. Conclusions The estimated total fatty acid delivered to skin from cleansing is comparable to the amount of fatty acid in a corneum layer. The delivered fatty acid is most likely incorporated in the corneum lipid phase.

A series of H2@C60 derivatives covalently linked to a nitroxide radical has been synthesized. We report distance-dependent nuclear spin relaxivity of H2 in these derivatives. The results clearly indicate that the relaxivity of H2 is distance-dependent and in good agreement with the Solomon−Bloembergen equation, which predicts a 1/r6 dependence.

VUV absorbance and index of refraction data for a series of linear and cyclic alkanes have been collected in order to understand the relationship between the electronic excitation wavelength (or absorbance edge), index of refraction, and molecular structure. The absorbance edge and index for a homologous series of both linear and cyclic alkanes increase with increasing carbon number. The optical properties of complex cycloalkanes do not vary predictably with increasing carbon number but instead depend on variations in the hydrocarbon structure in addition to hydrocarbon size. An understanding of the fundamental optical properties of this class of compounds is directly applicable to the identification of a high index and low-absorbance fluid for 193 nm immersion lithography.

The location of ring-substituted ketones, such as 2-phenylcycloalkanones in surfactant solutions, is readily characterized by FT-IR spectroscopy, since the sensitivity of the carbonyl group stretching vibration to changes in hydrogen bonding makes this an effective reporter for hydrophobic micellar core environments versus hydrophilic aqueous environments. Thus, FT-IR provides a direct means of examining the relative distribution of the probes between the micellar and aqueous environments and also allows elucidation of the factors that influence probe distributions. These factors include the hydrophobicity (ring-size, degree of substitution) and conformational flexibility of the ketone probes, as well as the nature of the surfactant and the size of micelles formed by the surfactant. FT-IR is employed to investigate the probe distribution as a function of all of these factors.

The search for successful generation 3 immersion lithography fluids is focused on high refractive index fluids which are transparent to 193 nm light. This search has led to saturated hydrocarbons which have been shown potential in this field. This paper discusses our observations that many immersion fluid candidates (saturated hydrocarbons and acetonitrile) were observed to polymerize upon irradiation with 193 nm light.

Interactions between reactive free radicals (r) with stable mononitroxyl radicals (N) and bisnitroxyl radicals (N-X-N) were studied by time-resolved electron paramagnetic resonance (TR-EPR). Reactive spin-polarized free radicals (r#), with non-Boltzmann population of spin states were produced by laser flash photolysis of benzil dimethyl monoketal or of (2,4,6-trimethylbenzoyl)diphenyl phosphine oxide (the superscript # symbol indicates electron spin polarization). Both isotopically symmetric nitroxyl biradicals (14N-X-14N) and isotopically asymmetric nitroxyl biradicals, with one nitroxyl bearing 15N and the other nitroxyl bearing 14N (14N-X-15N), were employed as probes of the spin exchange and chemical interactions between r and the nitroxyl biradicals. The interaction of r# with the asymmetric ortho-nitroxyl biradical (14N-O-15N), which exists in a condition of strong spin exchange, proved to be particularly informative. In this case, spin polarized (14N-O-15N)# (product of spin exchange with r#) and two polarized monoradicals (r14N-O-15N)# and (14N-O-15Nr)# (products of chemical reaction with r#) were observed. The latter three species possess three distinct TR-EPR spectra with different line splittings. The relative cross sections for spin exchange (Rex) and chemical reaction (Rrxn) were achieved through computer simulation of the TR-EPR spectra. The cross section for spin exchange, Rex, between r# and (N-X-N) biradical is estimated to be 4-6 times larger than the cross section of chemical reaction, Rrxn, between r# and (N-X-N). The para-nitroxyl biradical (14N-P-15N) exists in weak spin exchange, and behaves as an equimolar mixture of 14N and 15N mononitroxyls.

Generation-three (Gen-3) immersion lithography can be an enabler for the 32nm half-pitch node. For Gen-3 lithography to be successful, however, there must be three major breakthroughs in materials development: high refractive index ("high-index") lenses, high-index immersion fluids, and high-index photo-resists. Currently a material for a high-index lens element, lutetium aluminum garnet (LuAG), has been identified. However, suitable materials choices remain elusive for both the Gen-3 fluid and resist. This paper reviews the successes and failures in the search for Gen-3 high-index materials.

SynopsisObjective Skin irritation in personal cleansing has been correlated with surfactant binding with stratum corneum proteins. Polar and non-polar oils are increasingly being used in cleansing formulations which contain high (10–15%) level of anionic and non-ionic surfactants. However, the effects of oils in modulating skin damage from a cleansing product have not been studied in any detail. The objectives of this study are to determine whether low-viscosity polar and non-polar oils differ in their ability to reduce surfactant-induced skin irritation and, if so, how it might be related to their interactions with proteins. Methods Surfactant-induced skin irritation was measured by a 14-day in vivo cumulative patch irritation test. The methodology was similar to the well-known soap chamber test. Surfactant interactions with the water-soluble protein, bovine serum albumin (BSA), in the presence of oils were measured by conductometric titration. The effects of low-viscosity polar and non-polar oils on stratum corneum protein dynamics in the sulfhydryl group region were studied by electron paramagnetic resonance (EPR) using the covalently bound spin-label 3-maleimido-proxyl (5-MSL). EPR measurements were performed with stratum corneums obtained from discarded skins of 3- to 4-week-old female pigs. Simulation of the complex spectra provided insights on the environment and mobility of the protein-bound spin label. Results Addition of 1% polar sunflower seed oil (viscosity 42 centipoise) reduced in vivo irritation of 1% sodium lauryl ether sulphate with two ethoxylate/cocamidopropyl betaine (SLES/CAPB) by 20%, whereas 1% non-polar mineral oil (viscosity 15 centipoise) had no effect. Polar oil glyceryl trioleate (a major component in sunflower seed oil) at 10% level reduced surfactant binding to BSA protein in water by 40%, whereas the non-polar oil dodecane (a major component of mineral oil) at a similar level did not have any effect. The mobility of the spin label in a dry corneum was very low and was increased significantly with the addition of water and glycerol trioleate but less so with mineral oil. Conclusion Sunflower seed oil reduces surfactant-induced in vivo skin irritation more than mineral oil. This is possibly due to stronger interaction of polar oil with proteins, thus protecting it from surfactant binding.

In this report, we describe a versatile photochemical method for cross-linking polymer films and demonstrate that this method can be used to inhibit thin polymer films from dewetting. A bifunctional photoactive molecule featuring two benzophenone chromophores capable of abstracting hydrogen atoms from various donors, including C-H groups, is mixed into PS films. Upon exposure to UV light, the bis-benzophenone molecule cross-links the chains presumably by hydrogen abstraction followed by radical recombination. Photoinduced cross-linking is characterized by infrared spectroscopy and gel permeation chromatography. Optical and atomic force microscopy images show that photocrosslinked polystyrene (PS) thin films resist dewetting when heated above the glass transition temperature or exposed to solvent vapor. PS films are inhibited from dewetting on both solid and liquid substrates. The effectiveness of the method to inhibit dewetting is studied as a function of the ratio of cross-linker to macromolecule, duration of exposure to UV light, film thickness, the driving force for dewetting, and the thermodynamic nature of the substrate.

Sensitive and structurally specific methods for investigating silicalite external surface have been developed using electron paramagnetic resonance (EPR). The absorption of an EPR silent probe orth...

Photolysis of the supramolecular complexes (dibenzyl ketones@ZSM-5) produced supramolecular complexes of benzyl radicals@ZSM-5, which were directly detected by CW-EPR spectroscopy, and provided information on the dynamics of the radicals. The lifetimes of the radicals increased as the group X attached to the carbon atom at the radical center increases from X = H (t(1/2) ca. 2 min) to X = (CH(2))(4)CH(3) (t(1/2)200 min). In addition, line broadening of the EPR signal was observed as the group X increases. Experiments involving cation-exchanged zeolites (MZSM-5; M = Li, Na, K, Rb, Cs) showed a strong dependence of the radical lifetime on the size of the cation (t(1/2) ca. 10 min for Li and t(1/2)200 min for Cs). The results are discussed in terms of supramolecular steric effects on the radical-radical reactions in the zeolite supercages.

Photolysis of ketones (1, 1-oMe, 2, 2-oMe, 3, and 4) adsorbed on ZSM-5 zeolites produces persistent carbon-centered radicals that can be readily observed by conventional steady-state EPR spectroscopy. The radicals are persistent for time periods of seconds to many hours depending on the supramolecular structure of the initial radical@zeolite complex and the diffusion and reaction dynamics of radicals produced by photolysis. The structures of the persistent radicals responsible for the observed EPR spectra are determined by a combination of alternate methods of generation of the same radical, by deuterium substitution, and by spectral simulation. A clear requirement for persistence is that the radicals produced by photolysis must either separate and diffuse from the external to the internal surface or be generated within the internal surface and separate and diffuse apart. The persistence of radicals located on the internal surface is the result of inhibition of radical-radical reactions. Radicals that are produced on the external surface and whose molecular structure prevents diffusion into the internal surface are transient because radical-radical reactions occur rapidly on the external surface. The reactions of the persistent radicals with oxygen and nitric oxide were directly studied in situ by EPR analysis. In the case of reaction with oxygen, persistent peroxy radicals are formed in high yield. The addition of nitric oxide scavenges persistent radicals and leads initially to a diamagnetic nitroso compound, which is transformed into a persistent nitroxide radical by further photolysis. The influence of variation of radical structure on transience/persistence is discussed and correlated with supramolecular structure and reactivity of the radicals and their parent ketones.

We report an inelastic neutron scattering (INS) study of H2 molecule encapsulated inside the fullerene C60 which confirms the recently predicted selection rule, the first to be established for the INS spectroscopy of aperiodic, discrete molecular compounds. Several transitions from the ground state of para-H2 to certain excited translation-rotation states, forbidden according to the selection rule, are systematically absent from the INS spectra, thus validating the selection rule with a high degree of confidence. Its confirmation sets a precedent, as it runs counter to the widely held view that the INS spectroscopy of molecular compounds is not subject to any selection rules.

Inelastic neutron scattering (INS) has been employed to investigate the quantum dynamics of water molecules permanently entrapped inside the cages of C60 fullerene molecules. This study of the supramolecular complex, H2O@C60, provides the unique opportunity to study isolated water molecules in a highly symmetric environment. Free from strong interactions, the water molecule has a high degree of rotational freedom enabling its nuclear spin isomers, ortho-H2O and para-H2O to be separately identified and studied. The INS technique mediates transitions between the ortho and para spin isomers and using three INS spectrometers, the rotational levels of H2O have been investigated, correlating well with the known levels in gaseous water. The slow process of nuclear spin conversion between ortho-H2O and para-H2O is revealed in the time dependence of the INS peak intensities over periods of many hours. Of particular interest to this study is the observed splitting of the ground state of ortho-H2O, raising the three-fold degeneracy into two states with degeneracy 2 and 1 respectively. This is attributed to a symmetry-breaking interaction of the water environment.

Inelastic neutron scattering (INS) has been employed to investigate the quantum dynamics of water molecules permanently entrapped inside the cages of C60 fullerene molecules. This study of the supramolecular complex, H2O@C60, provides the unique opportunity to study isolated water molecules in a highly symmetric environment. Free from strong interactions, the water molecule has a high degree of rotational freedom enabling its nuclear spin isomers, ortho-H2O and para-H2O to be separately identified and studied. The INS technique mediates transitions between the ortho and para spin isomers and using three INS spectrometers, the rotational levels of H2O have been investigated, correlating well with the known levels in gaseous water. The slow process of nuclear spin conversion between ortho-H2O and para-H2O is revealed in the time dependence of the INS peak intensities over periods of many hours. Of particular interest to this study is the observed splitting of the ground state of ortho-H2O, raising the three-fold degeneracy into two states with degeneracy 2 and 1 respectively. This is attributed to a symmetry-breaking interaction of the water environment.

We report an inelastic neutron scattering (INS) study of a H2 molecule encapsulated inside the fullerene C60 which confirms the recently predicted selection rule, the first to be established for the INS spectroscopy of aperiodic, discrete molecular compounds. Several transitions from the ground state of para-H2 to certain excited translation-rotation states, forbidden according to the selection rule, are systematically absent from the INS spectra, thus validating the selection rule with a high degree of confidence. Its confirmation sets a precedent, as it runs counter to the widely held view that the INS spectroscopy of molecular compounds is not subject to any selection rules.

The water-endofullerene H2O@C60 provides a unique chemical system in which freely rotating water molecules are confined inside homogeneous and symmetrical carbon cages. The spin conversion between the ortho and para species of the endohedral H2O was studied in the solid phase by low-temperature nuclear magnetic resonance. The experimental data are consistent with a second-order kinetics, indicating a bimolecular spin conversion process. Numerical simulations suggest the simultaneous presence of a spin diffusion process allowing neighbouring ortho and para molecules to exchange their angular momenta. Cross-polarization experiments found no evidence that the spin conversion of the endohedral H2O molecules is catalysed by (13)C nuclei present in the cages.

We synthesized two molecular systems, in which an endofullerene C60 , incarcerating one hydrogen molecule (H2 @C60 ) and a nitroxide radical are connected by a folded 310 -helical peptide. The difference between the two molecules is the direction of the peptide orientation. The nuclear spin relaxation rates and the para → ortho conversion rate of the incarcerated hydrogen molecule were determined by (1) H NMR spectroscopy. The experimental results were analyzed using DFT-optimized molecular models. The relaxation rates and the conversion rates of the two peptides fall in the expected distance range. One of the two peptides is particularly rigid and thus ideal to keep the H2 @C60 /nitroxide separation, r, as large and controlled as possible, which results in particularly low relaxation and conversion rates. Despite the very similar optimized distance, however, the rates measured with the other peptide are considerably higher and thus are compatible with a shorter effective distance. The results strengthen the outcome of previous investigations that while the para → ortho conversion rates satisfactorily obey the Wigner's theory, the nuclear spin relaxation rates are in excellent agreement with the Solomon-Bloembergen equation predicting a 1/r(6) dependence.

The nitroxides 1 and 1-oMe were employed as EPR probes for the investigation of the supramolecular structures and dynamics of organic molecules adsorbed on the external surfaces of two MFI zeolites (silicalite and ZSM-5). The results for the two zeolites are qualitatively similar, but depend quantitatively on the surface area of the external surface. Computational analysis of the EPR spectra as a function of loading of the probe is consistent with an initial strong association of the probes with the holes on the external surface, followed by a weaker binding to the framework of the external surface between the holes. The first supramolecular structure (binding to holes) fixes the motion of the probes and allows for an estimation of the average separation of the probes through EPR analysis of the dipole−dipole interaction. After saturation of the holes and the onset of the second supermolecular structure (binding to the framework), rapid diffusion of the probes on the framework occurs and provides a means ...

The bimolecular contribution, R1 (M−1 s−1), to the T1 of isolated H2 and H2O protons, as well as free H2O in organic solution, by paramagnetic metal complexes was determined. Isolation was achieved by encapsulation in a fullerene: H2 was trapped in pristine C60 or in C60 with a 13-atom opening, and H2O in an open-C60 with a 19-atom opening. The R1 values in the presence of the various M(acac)x complexes [M = Fe(III), Cr(III), Cu(II), Co(III)] scale with μeff2 of the metal complex. The R1 values were significantly smaller for the trapped species than the free H2O. Surprisingly, R1 was nearly identical for the all three endohedral proton pairs, even in different solvents. This suggests that the magnetic isolation effects of the carbon cage are not significantly affected by the solvent, the completeness of the carbon cage, or separation of the hydrogens by an oxygen atom.

The adsorption characteristics (binding distributions, location, interactions, supramolecular structures, kinetics) of two cyclic ketones, 2-phenylcyclododecanone (112) and 2-phenylcyclopentadecano...

Photochemical, magnetic resonance, adsorption isotherms, and surface area measurements have been integrated to investigate the surface coverage dependence of the supramolecular structure and dynamics of two isomeric ketones, oMeDBK (molecular cross section similar to that of o-xylene) and pMeDBK (molecular cross section similar to that of p-xylene), adsorbed on three forms of zeolites with the MFI structure:silicalite, ZSM-5, and LZ-105. For each zeolite, the two isomeric ketones display striking qualitative differences in the experimental responses as a function of surface coverage. These differences are assigned to coverage-dependent changes in the supramolecular structural, dynamic, and binding characteristics of the adsorbed ketones and of the adsorbed reactive intermediates produced by photolysis of the ketones. In the case of pMeDBK, this ketone is adsorbed into the cages and channels of the internal surface. The external surface consists of two sites for the binding of oMeDBK: pores or “holes”, an...

Monodisperse silicalite crystals (170 μm × 40 μm × 40 μm) have been synthesized and the 29Si spin−lattice relaxation rates have been measured by high-resolution solid-state NMR. Loading of 5 wt % p-xylene into the silicalite channel system reduces the 29Si spin−lattice relaxation time compared to that of empty silicalite. The relaxation time is unaffected when p-xylene was replaced by p-xylene-d10 of the same loading. This indicates that dipole−dipole coupling between protons of guest molecules and silicon atoms does not contribute significantly to the 29Si spin-relaxation time. A novel method employing aromatic endoperoxide is demonstrated for controlled addition of molecular oxygen into silicalite samples. The results showed that interaction with a paramagnetic oxygen molecule is not the only relaxation mechanism for 29Si nuclei, and that zeolite structural changes caused by loaded organic guest molecules also play an important role in determining the 29Si spin−lattice relaxation time.

Hydrogen is one of the few molecules which has been incarcerated in the molecular cage of C$_{60}$ and forms endohedral supramolecular complex H$_2$@C$_{60}$. In this confinement hydrogen acquires new properties. Its translational motion becomes quantized and is correlated with its rotations. We applied infrared spectroscopy to study the dynamics of hydrogen isotopologs H$_2$, D$_2$ and HD incarcerated in C$_{60}$. The translational and rotational modes appear as side bands to the hydrogen vibrational mode in the mid infrared part of the absorption spectrum. Because of the large mass difference of hydrogen and C$_{60}$ and the high symmetry of C$_{60}$ the problem is identical to a problem of a vibrating rotor moving in a three-dimensional spherical potential. The translational motion within the C$_{60}$ cavity breaks the inversion symmetry and induces optical activity of H$_2$. We derive potential, rotational, vibrational and dipole moment parameters from the analysis of the infrared absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H$_2$@C$_{60}$. The same parameters were used to predict H$_2$ energies inside C$_{70}$[Xu et al., J. Chem. Phys., {\bf 130}, 224306 (2009)]. We compare the predicted energies and the low temperature infrared absorption spectra of H$_2$@C$_{70}$., Comment: Updated author list

The photoexcitation of functionalized fullerenes to their paramagnetic triplet electronic state can be studied by pulsed electron paramagnetic resonance (EPR) spectroscopy, whereas the interactions of this state with the surrounding nuclear spins can be observed by a related technique: electron nuclear double resonance (ENDOR). In this study, we present EPR and ENDOR studies on a functionalized exohedral fullerene system, dimethyl[9-hydro (C60-Ih)[5,6]fulleren-1(9 H )-yl]phosphonate (DMHFP), where the triplet electron spin has been used to hyperpolarize, couple and measure two nuclear spins. We go on to discuss the extension of these methods to study a new class of endohedral fullerenes filled with small molecules, such as H 2 @C 60 , and we relate the results to density functional calculations.

Spectroscopic studies of recently synthesized endofullerenes, in which H₂, H₂O and other atoms and small molecules are trapped in cages of carbon atoms, have shown that although the trapped molecules interact relatively weakly with the internal environment they are nevertheless susceptible to appropriately applied external perturbations. These properties have been exploited to isolate and study samples of H₂ in C₆₀ and other fullerenes that are highly enriched in the para spin isomer. Several strategies for spin-isomer enrichment, potential extensions to other endofullerenes and possible applications of these materials are discussed.

The interactions and structure of complexes formed between bovine serum albumin (BSA) and the anionic surfactant sodium dodecyl sulfate has been investigated by spectroscopic probe techniques. Steady state and time-resolved fluorescence, electron spin resonance, and deuterium NMR spectroscopy have been employed as a multitechnique approach to investigate the structures which occur along the proteinsurfactant isotherm. Three models of the protein-surfactant complex are considered. The results of the multitechnique approach are consistent with a structure which is predominantly of the "necklace and bead" type in which the unfolded protein wraps around surfactant micelles.

The product distributions produced by the photoinduced dichlorination of n-dodecane (nD) and the photoinduced monochlorination of 1 -chlorododecane (1CD) adsorbed on two pentasil zeolites (silicalite and LZ- 105) have been investigated. The results are explained in terms of a supramolecular model for which the mobile and diffusing chlorination reagents (CWC12) enter the zeolite particle from the external surface and diffuse preferentially along the linear channels of the zeolite internal surface that contain immobile adsorbed nD (or 1CD) molecules. The model assumes that the outermost layer of adsorbed substrates is attacked preferentially, that the attack occurs at the proximal end of adsorbed nD molecules closest to the extemal surface, and that, after the first chlorination, the substrate molecules in an inner layer are protected from chlorination by "blocking" molecules parked in the outer layer. The model describes each substrate molecule adsorbed on the internal surface in terms of supramolecular isomeric structures that are capable of characterizing the specific void space sites occupied by the substrate. A detailed analysis of the results allows the conclusion that the compensating cations tend to be preferentially located in the zigzag channels rather than in the linear channels or intersections and that the variation of selectivity of chlorination with experimental conditions results from redistribution of the isomeric supramolecular structures.

Oxazolidinone-substituted enecarbamates represent a mechanistically rich system for the study of stereoelectronic, steric, and conformational effects on stereoselectivity and mode selectivity in (1)O(2) [2 + 2] and ene reactions. Photooxygenation of these enecarbamates with (1)O(2) leads to diastereomerically pure dioxetanes that decompose to yield an oxazolidinone carbaldehyde and one of the two enantiomers of methyldesoxybenzoin in enantiomeric excess. Stereoselectivity originates at the allylic stereocenter, a result supported by quenching studies, computational analysis, and deuterium solvent isotope effects. [reaction: see text]

(1)H NMR of two H(2)@C(60) nitroxide derivatives has been characterized indirectly by reducing to their corresponding hydroxylamines. Nuclear spin relaxation of the endohedral H(2) and external protons of the H(2)@C(60) nitroxide and its corresponding hydroxylamine were measured and analyzed. The observed spectra are consistent with negligible scalar coupling between the unpaired electron and the endo-H(2). An unexpectedly large bimolecular relaxivity induced in the hydroxylamine by the corresponding nitroxide can be explained by rapid hydrogen atom transfer between the two species.

Computer aided analysis of electron paramagnetic resonance (EPR) spectra of tetrachloro-dibenzodioxin labelled with a nitroxide radical (TCDD-T) was employed to investigate the adsorption of dioxin vapours onto two carbons, the activated carbon (AC) NORIT GL50 and a carbon directly taken from a waste incinerator (WI) plant, termed EVN.2, and a low-polar micelle-templated mesoporous silica, termed lpMTS. Several experimental conditions were varied to optimize the adsorption process and to mimic dioxin adsorption occurring in a WI plant. Solvent vapours did not perturb dioxin adsorption. EPR analysis suggested that the nitroxide labelled-dioxin interacted (dipole–dipole interactions) with oxygenated groups, mainly C–O–C groups of the carbon and siloxane groups of lpMTS. The kinetics of adsorption was analyzed at different flow rates. The adsorption was large for NORIT and lpMTS already after few seconds, but a complete adsorption was achieved with a slow kinetics, whereas the EVN.2 sample showed a negligible adsorption even after 1 min. The results are interpreted in terms of the surface characterization (SBET, pore volume and pore size distribution) of the adsorbents. The EPR method described in this study can provide useful and unique information on the adsorption process of dioxins onto microporous carbons and mesoporous MTSs. Moreover, this method may be applied to different adsorbates and porous adsorbents.

Bisadduct isomers of a H(2)@C(60) derivative with nitroxide addends have been synthesized, isolated and characterized. The (1)H NMRs of endohedral H(2) of the major isomers show well-separated chemical shifts, which could be useful for structural assignment and identification of the purity of the C(60) bisadduct isomers.

A mild moisturizing body wash with stearic acid, a key component of corneum lipids, and emollient soybean oil has been introduced in the market place. The objectives of this study are to determine the amount and the location of the stearic acid in the corneum after in vivo cleansing by the formulation.Clinical cleansing studies for one and five consecutive days were carried out with the formulation containing soybean oil or petroleum jelly (PJ). The free stearic acid in it was replaced by the fully deuterated variant. The amounts of stearic acid in 10 consecutive corneum tape strips were measured by liquid chromatograph-mass spectroscopy. Separately, electron paramagnetic resonance (EPR) measurements were taken with a porcine skin after a wash by the soybean oil formulation with its free fatty acid replaced by its spin probe analogue, 5-doxyl stearic acid.Deuterated stearic acid was detected in all 10 consecutive layers of stratum corneum and the total amount after five washes with the soybean oil formulation was 0.33 μg/cm². The spin probe in cleanser-treated skin was incorporated in a partially ordered hydrophobic region similar to corneum lipids. The probe mobility increased in the temperature region where lipid disorder was expected.The estimated total fatty acid delivered to skin from cleansing is comparable to the amount of fatty acid in a corneum layer. The delivered fatty acid is most likely incorporated in the corneum lipid phase.

The dominant products from the photolysis of large α-phenylcycloalkanones are the cyclophanes formed by the intramolecular para coupling of the acyl benzyl biradical intermediate. This tendency to form cyclophanes is preserved under a variety of environmental conditions (organic solvents, micelles, and zeolites)