Infrared spectroscopy of an endohedral water in fullerene.

An infrared absorption spectroscopy study of the endohedral water molecule in a solid mixture of H2O@C60 and C60 was carried out at liquid helium temperature. From the evolution of the spectra during the ortho-para conversion process, the spectral lines were identified as para-H2O and ortho-H2O transitions. Eight vibrational transitions with rotational side peaks were observed in the mid-infrared: ω1, ω2, ω3, 2ω1, 2ω2, ω1 + ω3, ω2 + ω3, and 2ω2 + ω3. The vibrational frequencies ω2 and 2ω2 are lower by 1.6% and the rest by 2.4%, as compared to those of free H2O. A model consisting of a rovibrational Hamiltonian with the dipole and quadrupole moments of H2O interacting with the crystal field was used to fit the infrared absorption spectra. The electric quadrupole interaction with the crystal field lifts the degeneracy of the rotational levels. The finite amplitudes of the pure v1 and v2 vibrational transitions are consistent with the interaction of the water molecule dipole moment with a lattice-induced electric field. The permanent dipole moment of encapsulated H2O is found to be 0.50 ± 0.05 D as determined from the far-infrared rotational line intensities. The translational mode of the quantized center-of-mass motion of H2O in the molecular cage of C60 was observed at 110 cm-1 (13.6 meV).

[Informal care for dementia according to type of service]. / Informelle Pflege bei Demenz nach Leistungsarten.

BACKGROUND: Dementia is a major challenge for society and its impact will grow in the future. Informal care is an essential part of dementia care. Previous studies considered informal care as a whole and not by its components. OBJECTIVE: We aimed to assess the degree of association between specific informal care services and dementia. MATERIAL AND METHODS: This analysis is based on data from the seventh wave of the AgeCoDe/AgeQualiDe study. Dementia was diagnosed based on the DSM-IV criteria. Severity of dementia was assessed and categorized by means of the Clinical Dementia Rating and eight individual informal care services were considered. Logistic regression models were used to assess associations. RESULTS: Of the 864 participants 18% suffered from dementia (very mild: 4%; mild: 6%; moderate: 5%; severe: 3%). All informal care services were significantly associated with dementia, with an emphasis on "supervision", "regulation of financial matters" and "assistance in the intake of medication". Considering different degrees of dementia severity, similar results arose from the analyses. All three aforementioned services showed a pronounced association with all degrees of dementia severity, except for supervision and very mild dementia. CONCLUSION: The provision of all types of informal care services is associated with dementia. The association is pronounced for services that can be more easily integrated into the daily routines of the informal caregiver. Policy makers who plan to integrate informal care into the general care arrangements for dementia should consider this.

Does Visual Impairment Affect Social Ties in Late Life? Findings of a Multicenter Prospective Cohort Study in Germany.

OBJECTIVE: To investigate how visual impairment affects social ties in late life longitudinally. DESIGN: Population-based prospective cohort study. SETTING: Individuals in old age were recruited via general practitioners' offices (at six study centers) in Germany. They were interviewed every 18 months. PARTICIPANTS: Individuals aged 75 years and above at baseline. Follow-up wave 2 (36 months after baseline, n=2,443) and wave 4 (72 months after baseline, n=1,618) were used for the analyses presented here. MEASUREMENTS: Social ties were assessed using the 14-item form of the questionnaire for social support (F-SozU K-14). Visual impairment was self-rated on a three level Likert scale (no impairment, mild visual impairment, or severe/profound visual impairment). RESULTS: Adjusting for sociodemographic factors, hearing impairment and comorbidity, fixed effects regressions revealed that the onset of mild visual impairment decreased the social support score, in particular the emotional support score. Additionally, the onset of mild hearing impairment decreased the social support score in men. Moreover, increasing age decreased the social support score in the total sample and in both sexes. Loss of spouse and increasing comorbidity did not affect the social support score. CONCLUSION: Our results highlight the importance of visual impairment for social ties in late life. Consequently, appropriate strategies in order to delay visual impairment might help to maintain social ties in old age.

[Longitudinal Predictors of the Need for Care]. / Einflussfaktoren auf die Pflegebedürftigkeit im Längsschnitt.

Background: Little is known about the longitudinal predictors of the need for care in old age. However, the knowledge of these factors is important for developing strategies for prevention or delay the need for care. Thus, we aimed at investigating the factors affecting the need for care in old age. Methods: In this population-based prospective cohort study (AgeCoDe, with n=3 217 individuals aged 75 years and above at baseline), the need for care was observed over 4.5 years. The need for care was quantified by the care level defined by the German Law (§ 15 SGB XI). Longitudinal predictors (sociodemographic variables, impairment in mobility/hearing/vision, dementia and depression) of the need for care were examined by using Random Effects Logit regressions. Results: Longitudinal regression analysis revealed that the probability of the need for care significantly increased with the occurrence of dementia (OR: 48.2), mobility impairments (aggravated walking, OR: 26.4; disability of walking, OR: 747.9) and age (e. g. 90 years and above vs.<80 years, OR: 32.3). The influence of family status, living conditions, visual impairment and depression on need for care was markedly smaller, and the effect of hearing impairments did not achieve statistical significance. Conclusion: In order to prevent or delay the need for care in old age, treatments should aim at preserving mobility and cognition. Due to demographic ageing, developing such programs is of major importance for health policy.

Predictors of Frailty in Old Age - Results of a Longitudinal Study.

OBJECTIVES: To investigate time-dependent predictors of frailty in old age longitudinally. DESIGN: Population-based prospective cohort study. SETTING: Elderly individuals were recruited via GP offices at six study centers in Germany. The course of frailty was observed over 1.5 years (follow up wave 4 and follow up wave 5). PARTICIPANTS: 1,602 individuals aged 80 years and older (mean age 85.4 years SD 3.2, with mean CSHA CFS 3.5 SD 1.6) at follow up wave 4. MEASUREMENTS: Frailty was assessed by using the Canadian Study of Health and Aging Clinical Frailty Scale (CSHA CFS), ranging from 1 (very fit) to 7 (severely frail). RESULTS: Fixed effects regressions revealed that frailty increased significantly with increasing age (ß=.2) as well as the occurrence of depression (ß=.5) and dementia (ß=.8) in the total sample. Changes in marital status and comorbidity did not affect frailty. While the effects of depression and dementia were significant in women, these effects did not achieve statistical significance in men. CONCLUSION: Our findings highlight the role of aging as well as the occurrence of dementia and depression for frailty. Specifically, in order to delay frailty in old age, developing interventional strategies to prevent depression might be a fruitful approach.

Benzene at 1GHz. Magnetic field-induced fine structure.

The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting Δν. The magnitude of Δν observed for the central resonance is smaller than that observed for the (13)C satellite doublets Δν'. This difference, Δ(Δν)=Δν'-Δν, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the (13)C and (2)H spectra to determine the relative signs of the indirect coupling, JCD, and Δν. The positive sign found for Δν is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of Δν is decreased by the pair correlations in this prototypical molecular liquid.

Quantum rotation and translation of hydrogen molecules encapsulated inside C60: temperature dependence of inelastic neutron scattering spectra.

The quantum dynamics of a hydrogen molecule encapsulated inside the cage of a C60 fullerene molecule is investigated using inelastic neutron scattering (INS). The emphasis is on the temperature dependence of the INS spectra which were recorded using time-of-flight spectrometers. The hydrogen endofullerene system is highly quantum mechanical, exhibiting both translational and rotational quantization. The profound influence of the Pauli exclusion principle is revealed through nuclear spin isomerism. INS is shown to be exceptionally able to drive transitions between ortho-hydrogen and para-hydrogen which are spin-forbidden to photon spectroscopies. Spectra in the temperature range 1.6≤T≤280 K are presented, and examples are given which demonstrate how the temperature dependence of the INS peak amplitudes can provide an effective tool for assigning the transitions. It is also shown in a preliminary investigation how the temperature dependence may conceivably be used to probe crystal field effects and inter-fullerene interactions.

Infrared spectroscopy of small-molecule endofullerenes.

Hydrogen is one of the few molecules that has been incarcerated in the molecular cage of C60 to form the endohedral supramolecular complex H2@C60. In this confinement, hydrogen acquires new properties. Its translation motion, within the C60 cavity, becomes quantized, is correlated with its rotation and breaks inversion symmetry that induces infrared (IR) activity of H2. We apply IR spectroscopy to study the dynamics of hydrogen isotopologues H2, D2 and HD incarcerated in C60. The translation and rotation modes appear as side bands to the hydrogen vibration mode in the mid-IR part of the absorption spectrum. Because of the large mass difference of hydrogen and C60 and the high symmetry of C60 the problem is almost identical to a vibrating rotor moving in a three-dimensional spherical potential. We derive potential, rotation, vibration and dipole moment parameters from the analysis of the IR absorption spectra. Our results were used to derive the parameters of a pairwise additive five-dimensional potential energy surface for H2@C60. The same parameters were used to predict H2 energies inside C70. We compare the predicted energies and the low-temperature IR absorption spectra of H2@C70.

Anisotropic nuclear spin interactions in H2O@C60 determined by solid-state NMR.

We report a solid-state NMR study of the anisotropic nuclear spin interactions in H2O@C60 at room temperature. We find evidence of significant dipole-dipole interactions between the water protons, and also a proton chemical shift anisotropy (CSA) interaction. The principal axes of these interaction tensors are found to be perpendicular. The magnitude of the CSA is too large to be explained by a model in which the water molecules are partially aligned with respect to an external axis. The evidence indicates that the observed CSA is caused by a distortion of the geometry or electronic structure of the fullerene cages, in response to the presence of the endohedral water.

Infrared spectroscopy of endohedral HD and D2 in C60.

We report on the dynamics of two hydrogen isotopomers, D(2) and HD, trapped in the molecular cages of a fullerene C(60) molecule. We measured the infrared spectra and analyzed them using a spherical potential for a vibrating rotor. The potential, vibration-rotation Hamiltonian, and dipole moment parameters are compared with previously studied H(2)@C(60) parameters [M. Ge, U. Nagel, D. Hüvonen, T. Rõõm, S. Mamone, M. H. Levitt, M. Carravetta, Y. Murata, K. Komatsu, J. Y.-C. Chen, and N. J. Turro, J. Chem. Phys. 134, 054507 (2011)]. The isotropic part of the potential is similar for all three isotopomers. In HD@C(60), we observe mixing of the rotational states and an interference effect of the dipole moment terms due to the displacement of the HD rotation center from the fullerene cage center.

Interaction potential and infrared absorption of endohedral H2 in C60.

We have measured the temperature dependence of the infrared spectra of a hydrogen molecule trapped inside a C(60) cage, H(2)@C(60), in the temperature range from 6 to 300 K and analyzed the excitation spectrum by using a five-dimensional model of a vibrating rotor in a spherical potential. The electric dipole moment is induced by the translational motion of endohedral H(2) and gives rise to an infrared absorption process where one translational quantum is created or annihilated, ΔN = ±1. Some fundamental transitions, ΔN = 0, are observed as well. The rotation of endohedral H(2) is unhindered but coupled to the translational motion. The isotropic and translation-rotation coupling part of the potential are anharmonic and different in the ground and excited vibrational states of H(2). The vibrational frequency and the rotational constant of endohedral H(2) are smaller than those of H(2) in the gas phase. The assignment of lines to ortho- and para-H(2) is confirmed by measuring spectra of a para enriched sample of H(2)@C(60) and is consistent with the earlier interpretation of the low temperature infrared spectra [Mamone et al., J. Chem. Phys. 130, 081103 (2009)].

Rotor in a cage: Infrared spectroscopy of an endohedral hydrogen-fullerene complex.

We report the observation of quantized translational and rotational motion of molecular hydrogen inside the cages of C(60). Narrow infrared absorption lines at the temperature of 6 K correspond to vibrational excitations in combination with translational and rotational excitations and show well-resolved splittings due to the coupling between translational and rotational modes of the endohedral H(2) molecule. A theoretical model shows that H(2) inside C(60) is a three-dimensional quantum rotor moving in a nearly spherical potential. The theory provides both the frequencies and the intensities of the observed infrared transitions. Good agreement with the experimental results is obtained by fitting a small number of empirical parameters to describe the confining potential, as well as the relative concentration of ortho- and para-H(2).

Quantum translator-rotator: inelastic neutron scattering of dihydrogen molecules trapped inside anisotropic fullerene cages.

We report an inelastic neutron scattering investigation of the quantum dynamics of hydrogen molecules trapped inside anisotropic fullerene cages. Transitions among the manifold of quantized rotational and translational states are directly observed. The spectra recorded as a function of energy and momentum transfer are interpreted in terms of the rotational potential and the cage dimensions. The thermodynamics of orthohydrogen and parahydrogen are investigated through temperature dependence measurements.

Thermal history effects and methyl tunneling dynamics in a supramolecular complex of calixarene and para-xylene.

The low-temperature structure and dynamics of guest molecules of p-xylene incorporated in the isopropyl-calix[4] arene(2:1) p-xylene complex have been investigated by solid state nuclear magnetic resonance (NMR). Using one-dimensional 1H-decoupled 13C cross-polarization magic-angle-spinning (MAS) NMR and two-dimensional 1H-13C correlation spectroscopy, a full assignment of the 13C and 1H chemical shifts has been made. Using 1H NMR relaxometry, the effects of thermal history on the structure of the system have been investigated. Rapidly cooled samples have 1H spin-lattice relaxation times T1, which at low temperature (T<60 K) are typically two orders of magnitude faster than those observed in annealed samples which have been cooled slowly over many hours. In both forms, the low-temperature relaxation is driven by the dynamics of the weakly hindered methyl rotors of the p-xylene guest. The substantial difference in T1 is attributed in the rapidly cooled sample to disorder in the structure of the complex leading to a wide distribution of correlation times and methyl barrier heights. A comparison of the linewidths and splittings in the high resolution 13C MAS spectra of the two forms provides structural insight into the nature of the disorder. Using 1H field-cycling NMR relaxometry, the methyl dynamics of the p-xylene guest in the annealed sample have been fully characterized. The B-field dependence of the 1H T1 maps out the spectral density from which the correlation times are directly measured. The methyl barrier heights are determined from an analysis of the temperature dependence.

Solid-state NMR of endohedral hydrogen-fullerene complexes.

We present an overview of solid-state NMR studies of endohedral H(2)-fullerene complexes, including (1)H and (13)C NMR spectra, (1)H and (13)C spin relaxation studies, and the results of (1)H dipole-dipole recoupling experiments. The available data involves three different endohedral H(2)-fullerene complexes, studied over a wide range of temperatures and applied magnetic fields. The symmetry of the cage influences strongly the motionally-averaged nuclear spin interactions of the endohedral H(2) species, as well as its spin relaxation behaviour. In addition, the non-bonding interactions between fullerene cages are influenced by the presence of endohedral hydrogen molecules. The review also presents several pieces of experimental data which are not yet understood, one example being the structured (1)H NMR lineshapes of endohedral H(2) molecules trapped in highly symmetric cages at cryogenic temperatures. This review demonstrates the richness of NMR phenomena displayed by H(2)-fullerene complexes, especially in the cryogenic regime.