Tautomerism and 1H and 13C NMR assignment of methyl derivatives of 9-hydroxyphenalenone

9-Hydroxyphenalenone is a planar multicyclic beta-keto-enol that demonstrates C2V symmetry on the NMR timescale. Off-axis substitution breaks the molecular symmetry and results in tautomers. 1H and 13C NMR assignments were made for 9-hydroxyphenalenone and three methyl derivatives, and the solution-phase tautomers were determined.     

The effect of selenium incorporation on the bandwidth and conductivity of neutral radical conductors

The first example of an undimerized pi-stacked bis-1,2,3-thiaselenazolyl radical displays improved bandwidth and conductivity relative to an isostructural bis-1,2,3-dithiazolyl.     

The constant neutral linked magnetic field electric sector scan

A linked magnetic field-electric sector scan for which (B/E)\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {1 - E} $\end{document} is constant selectively records first field free region metastable peaks representing loss of the same neutral fragment. The constant neutral metastable ion spectra produced by this scan should provide information about the presence and location of particular functional groups beyond that which is available from focused mass spectra. Constant neutral linked scans can be obtained consecutively with focused spectra and with B/E and B ²/E linked scans by simple extension of a computerized B-E scanning method developed previously.     

Mechanism of ammonia detection by chemically functionalized single-walled carbon nanotubes: in situ electrical and optical study of gas analyte detection

We provide definitive evidence for the mechanism of electronic detection of ammonia by monitoring in situ changes in the electrical resistance and optical spectra of films of poly(m-aminobenzenesulfonic acid)-functionalized SWNTs (SWNT-PABS). The increase of resistance during exposure to ammonia is associated with deprotonation of the PABS side chain that in turn induces electron transfer between the oligomer and the valence band of the semiconducting SWNTs. Near IR spectroscopy is used to demonstrate that the charge transfer is a weakly driven process, and this accounts for the high reversibility of the sensor. We show that the sensitivity of the chemiresistors increases as the film thickness is reduced to the percolation threshold and that the SWNT-PABS film thickness provides a simple means to enhance the electronic response.     

Synthesis, crystal structure, and physical properties of sterically unprotected hydrocarbon radicals

We have prepared and isolated neutral polycyclic hydrocarbon radicals. A butyl-substituted radical gave single crystals, in which a π-dimeric structure, not a σ-bonded dimer, was observed, even though steric protection was absent. Thermodynamic stabilization due to the highly spin-delocalized structure contributes effectively to the suppression of σ-bond formation.     

Trisphenalenyl-based neutral radical molecular conductor

We report the preparation, crystallization, and solid-state characterization of the first member of a new family of tris(1,9-disubstituted phenalenyl)silicon neutral radicals. In the solid state, the radical packs as weak partial pi-dimers with intermolecular carbon...carbon contacts that fall at the van der Waals atomic separation. Magnetic susceptibility measurements indicate approximately 0.7 Curie spins per molecule from room temperature down to 50 K, below which antiferromagnetic coupling becomes apparent; the compound has a room-temperature single-crystal conductivity of sigmaRT = 2.4 x 10(-6) S cm(-1).     

Tetrathiophenalenyl radical and its disulfide-bridged dimer

The presence of two disulfide groups in the tetrathiophenalenyl radical TTPLY leads to a highly delocalized spin distribution and the lowest cell potential ever observed for a monofunctional phenalenyl derivative. While the heteroatom substituents successfully block C-C bond formation, TTPLY nonetheless associates in the solid state to afford the hypervalent S-S-bonded dimer (TTPLY)2.