Conductance fluctuations in cobalt valence tautomer molecular thin films.

The conductivity changes associated with optical excitations and changing temperature in cobalt valence tautomer molecular thin films were investigated. Conductance switching in the presence of illumination is observed, with occasional locking in a higher conductance state, depending on the temperature, the photon energy of the illumination, and the bias voltage. Light of sufficiently short wavelengths is needed to ensure the light enhanced conductance switching, consistent with the optical absorption, but bias voltage clearly plays a role as well.

Electronic structure of cobalt valence tautomeric molecules in different environments.

Future molecular microelectronics require the electronic conductivity of the device to be tunable without impairing the voltage control of the molecular electronic properties. This work reports the influence of an interface between a semiconducting polyaniline polymer or a polar poly-D-lysine molecular film and one of two valence tautomeric complexes, , [Co(SQ)(Cat)(4-CN-py)] ↔ [Co(SQ)(4-CN-py)] and [Co(SQ)(Cat)(3-tpp)] ↔ [Co(SQ)(3-tpp)]. The electronic transitions and orbitals are identified using X-ray photoemission, X-ray absorption, inverse photoemission, and optical absorption spectroscopy measurements that are guided by density functional theory.

Evidence of dynamical effects and critical field in a cobalt spin crossover complex.

The [Co(SQ)(4-CN-py)] complex exhibits dynamical effects over a wide range of temperature. The orbital moment, determined by X-ray magnetic circular dichroism (XMCD) with decreasing applied magnetic field, indicates a nonzero critical field for net alignment of magnetic moments, an effect not seen with the spin moment of [Co(SQ)(4-CN-py)].