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We report the preparation and solid state characterization of a silicon (IV) salt based on a new redox active tripodal hexadentate ligand [H3L = l,l,l-Tris(l′-oxophenalenyl-9′-N-methyl) ethane]. X-ray analysis of the complex reveals a short Si-N bond distance (av 1.878(16)). The compound is shown to undergo three reversible one-electron reduction steps (without decomposition) due to the formation of radical, anion and dianion of the phenalenyl moiety.

We report the crystal structure of a spiro-bis(1,9-disubstituted-phenalenyl)boron cation ( 2 + ) and by comparison with the structures of a series of radicals we conclude that the changes in bond lengths in the radicals compared to those of the corresponding cation can be qualitatively predicted by the sign of the partial bond order of the singly occupied molecular orbital (SOMO), which contains the additional electron. By use of this information, we can analyse the structures of the π-dimer radicals 1 and 2 and ascertain the location of the unpaired electron in these compounds. Where these radicals exist as paramagnetic π-dimers (high-temperature regime), the unpaired electrons reside mainly in the phenalenyl units not directly involved in the π-dimer interaction. At low temperatures, where the diamagnetic π-dimers exist, the electrons localise in the phenalenyl units directly involved in the π-dimer, but there still exists some degree of delocalisation of the electrons to the other halves of the molecules. We postulate that the increase in delocalisation of the unpaired electrons is related to the increase of the conductivity by about two orders of magnitude as the electrons spin pair.

We compare the changes in the transmission (τ) spectra of blue bronze caused by changing temperature (Δτ T ) and by polarizing the charge-density-wave (CDW) with an electric field near threshold (Δτ V ), for photon energies between 800 and 1200 cm −1 . Unlike at lower energies, the two spectra differ qualitatively in this spectral region, near the edge of the CDW gap. While temperature mainly affects phonon damping, CDW polarization shifts phonon energies. Both Δτ v /τ and Δτ T /τ are expected to change sign for energies above the gap, but this occurs much more gradually (as a function of energy) in the electromodulated spectrum.

We have used electromodulated infrared transmission to study phase slip of the sliding charge-density wave at the current contacts in blue bronze. We have found that phase slip requires a smaller phase gradient at the positive contact than the negative and that the phase slip threshold voltage is approximately independent of temperature.