With support from the Chemistry Research Instrumentation and Facilities: Multi-User program (CRIF:MU), the Department of Chemistry at the University of Nevada, Reno will refurbish a nuclear magnetic resonance (NMR) spectrometer and upgrade it to provide modern solid-state NMR capabilities to the University. The new instrumentation will be employed in a wide variety of research projects including the synthesis of unusual polycyclic aromatic hydrocarbons, investigations of the three dimensional solid-state structure of peptides and proteins, studies of catalysts, analysis of fuel cell membranes, and the characterization of functional supramolecular polymers.
NMR spectroscopy is a widely used analytical tool in any molecular-synthetic discipline in chemistry. Spectra, obtained by detecting transitions between energy levels arising from the nuclear spin properties of atoms, provide information on the arrangement and connectivity of atoms in molecules and materials. These data enable researchers to identify unknown substances and to determine their structures. This particular instrument will analyze substances in the solid state thereby providing valuable structural information on a variety of insoluble materials. The instrumentation will also allow the incorporation of solid-state NMR experiments into undergraduate courses. This NMR spectrometer will be used by others in the Chemistry Department, investigators in the Chemical and Material Engineering Departments and by researchers throughout the state. As the only generally available solid-state NMR spectrometer in Nevada, the instrument is expected to have a broad impact on research and education in the state.
This award supported the acquisition and installation of a solid-state nuclear magnetic resonance (NMR) spectrometer in the Department of Chemistry of the University of Nevada, Reno. Just like an MRI instrument allows one to see inside the human body, the solid-state NMR spectrometer helps us understand the arrangement of atoms within a molecule. The solid-state aspect of this instrument is especially useful because it permits the study of solid, as opposed to liquid, samples. The chemical shift for a particular nucleus in a molecule is a function of alignment of the molecule to the external magnetic field. In liquid-state NMR, the rapid rotation of a molecule in solution averages out the chemical shift to a single value called the isotropic chemical shift. In a solid-state powder sample every orientation of the sample relative to the external magnetic field is present. This lead to peaks that are extremely broad with line widths greater than 1000 Hz. To overcome this problem the sample is spun at the magic angle, 54.74 degrees. This magic angle spinning averages out the chemical shift anisotropy (and dipolar couplings) and give a high-resolution spectrum. As proposed, we reused and existing superconducting magnet to keep the costs to a minimum. A few problems were encountered during the installation, but these were smoothed out and the instrument is working well. The final instrument comprises a 2-channel 400 MHz Tecmag Discovery with a NMR Service GmbH MAS H-X broadband probe that can rotate samples up to 18 kHz using a 4 mm rotor (Figure 1). Two projects in particular have benefited from this instrument. The Catalano research group has developed a set of metal-containing molecules whose color in fluorescence changes upon exposure to different solvent vapors. These materials could lead to new sensors for chemical and diagnostic testing. The King research group used this instrument to develop new polymers that extend regularly in two dimensions. They are shaped like sheets rather than threads of normal polymers. These materials are insoluble, and solid state NMR was essential to their development. We hope that these materials might help solve problems of economical desalination and carbon dioxide capture. The broader impact of this instrumentation extends beyond the potential applications described in the preceding paragraph. This instrument continues to serve training platform for many students. Two international visiting scholars made heavy use of the instrument during their stay, thus promoting international scientific collaborations.
