X-ray analysis has revealed that 4,4′-bipyridine, 1,2-bis(4-pyridyl)ethylene, and hexamethylenetetramine form donor-acceptor complexes with 1,4-diiodobenzene, 1,4-diiodotetrafluorobenzene, and tetraiodoethylene in which the N‚‚‚I distance is longer than that for the corresponding I 2 complexes. As opposed to the corresponding I 2 complexes that are molecular adducts, these complexes have extended structures and longer N‚‚‚I distances. Steric and electronic effects influence the strength of the N‚‚‚I interaction and the crystal packing. An additional complex of 1,2-bis(4-pyridyl)ethane and 1,4-dibromotetrafluorobenzene has also been investigated for comparison of N‚‚‚I and N‚‚‚Br interactions.

The thermal conductivity at 300 K of (10,10) carbon nanotubes that have been functionalized by chemical attachment of phenyl rings through covalent bonding (chemisorption) at random positions has been calculated as a function of adsorption density using classical trajectories. The system exhibits a rapid drop in thermal conductivity with chemisorption, where chemisorption to as little as 1.0% of the nanotube carbon atoms reduces the thermal conductivity by over a factor of 3. The simulation results indicate that the effect is due to a reduction in phonon scattering length rather than changes in the vibrational frequencies of the carbon atoms in the nanotube.

No abstract