The dipolar endofullerene HF@C60

The cavity inside fullerenes provides a unique environment for the study of isolated atoms and molecules. We report encapsulation of hydrogen fluoride inside C60 using molecular surgery to give the endohedral fullerene HF@C60. The key synthetic step is the closure of the open fullerene cage while minimizing escape of HF. The encapsulated HF molecule moves freely inside the cage and exhibits quantization of its translational and rotational degrees of freedom, as revealed by inelastic neutron scattering and infrared spectroscopy. The rotational and vibrational constants of the encapsulated HF molecules were found to be redshifted relative to free HF. The NMR spectra display a large 1H-19F J coupling typical of an isolated species. The dipole moment of HF@C60 was estimated from the temperature-dependence of the dielectric constant at cryogenic temperatures and showed that the cage shields around 75% of the HF dipole

Can H-2 inside C-60 communicate with the outside world?

The quenching rate constants of singlet oxygen by C-60, H-2@C-60, D-2@C-60, H-2, and D-2 in solution were measured. The presence of a hydrogen (H-2@C-60) or deuterium (D-2@C-60) molecule inside the fullerene did not produce any observable effect based on triplet lifetime or EPR measurements. However, a remarkable effect was found for the O-1(2) quenching by C-60, H-2@C-60, D-2@C-60, H-2, and D-2. Singlet oxygen was generated by photosensitization or by thermal decomposition of naphthalene endoperoxide derivatives. Comparison of the rate constants for quenching Of O-1(2) by H-2@C-60 and D-2@C-60 demonstrates a significant vibrational interaction between oxygen and H-2 inside the fullerene. The quenching rate constant for H-2 is 1 order of magnitude higher than that of D2, in agreement with the results observed for the quenching Of O-1(2) with H-2@C-60 or D-2@C-60

Can H-2 inside C-60 communicate with the outside world?

none8The quenching rate constants of singlet oxygen by C-60, H-2@C-60, D-2@C-60, H-2, and D-2 in solution were measured. The presence of a hydrogen (H-2@C-60) or deuterium (D-2@C-60) molecule inside the fullerene did not produce any observable effect based on triplet lifetime or EPR measurements. However, a remarkable effect was found for the O-1(2) quenching by C-60, H-2@C-60, D-2@C-60, H-2, and D-2. Singlet oxygen was generated by photosensitization or by thermal decomposition of naphthalene endoperoxide derivatives. Comparison of the rate constants for quenching Of O-1(2) by H-2@C-60 and D-2@C-60 demonstrates a significant vibrational interaction between oxygen and H-2 inside the fullerene. The quenching rate constant for H-2 is 1 order of magnitude higher than that of D2, in agreement with the results observed for the quenching Of O-1(2) with H-2@C-60 or [email protected]. LOPEZ-GEJO; A. A. MARTI; M. RUZZI; S. JOCKUSCH; K. KOMATSU; F. TANABE; Y. MURATA; N. J. TURROJ., LOPEZ GEJO; A. A., Marti; Ruzzi, Marco; S., Jockusch; K., Komatsu; F., Tanabe; Y., Murata; N. J., Turr

The Spin Chemistry and Magnetic Resonance of H(2)@C(60). From the Pauli Principle to Trapping a Long Lived Nuclear Excited Spin State inside a Buckyball

0ne of the early triumphs of quantum mechanics was Heisenberg's prediction, based on the Pauli principle and wave function symmetry arguments, that the simplest molecule, H(2), should exist as two distinct species-allotropes of elemental hydrogen. One allotrope, termed para-H(2) (pH(2)), was predicted to be a lower energy species that could be visualized as rotating like a sphere and possessing antiparallel (up arrow down arrow) nuclear spins; the other allotrope, termed ortho-H(2) (oH(2)), was predicted to be a higher energy state that could be visualized as rotating like a cartwheel and possessing parallel (up arrow up arrow) nuclear spins. This remarkable prediction was confirmed by the early 1930s, and pH(2) and oH(2) were not only separated and characterized but were also found to be stable almost indefinitely in the absence of paramagnetic "spin catalysts", such as molecular oxygen, or traces of paramagnetic impurities, such as metal ions. The two allotropes of elemental hydrogen, pH(2) and oH(2), may be quantitatively incarcerated in C(60) to form endofullerene guest@host complexes, symbolized as pH(2)@C(60) and oH(2)@C(60), respectively, How does the subtle difference in nuclear spin manifest itself when hydrogen allotropes are incarcerated in a buckyball? Can the incarcerated "guests" communicate with the outside world and vice versa? Can a paramagnetic spin catalyst in the outside world cause the interconversion of the allotropes and thereby effect a chemical transformation inside a buckyball? How dose are the measurable properties of H(2)@C(60) to those computed for the "quantum particle in a spherical box"? Are there any potential practical applications of this fascinating marriage of the simplest molecule, H(2), with one of the most beautiful of all molecules, C(60)? How can one address such questions theoretically and experimentally? A goal of our studies is to produce an understanding of how the H(2) guest molecules incarcerated in the host C(60) can "communicate" with the chemical world surrounding it. This world includes both the "walls" of the incarcerating host (the carbon atom "bride that compose the wall) and the "outside" world beyond the atoms of the host walls, namely, the solvent molecules and selected paramagnetic molecules added to the solvent that will have special spin interactions with the H(2) inside the complex. In this Account we describe the temperature dependence of the equilibrium of the interconversion of oH(2)@C(60) and pH(2)@C(60) and show how elemental dioxygen, O(2), a ground-state triplet is an excellent paramagnetic spin catalyst for this interconversion. We then describe an exploration of the spin spectroscopy and spin chemistry of H(2)@C(60). We find that H(2)@C(60) and its isotopic analogs, HD@C(60) and D(2)@C(60), provide a rich and fascinating platform on which to investigate spin spectroscopy and spin chemistry. Finally we consider the potential extension of spin chemistry to another molecule with spin isomers, H(2)O, and the potential applications of the use of pH(2)@C(60) as a source of latent massive nuclear polarization

Status of High-Index Materials for Generation-Three 193nm Immersion Lithography

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") tenses, 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