Chiral effects at the metal center in Fe(III) spin crossover coordination salts.

Evidence of chirality was observed at the Fe metal center in Fe(III) spin crossover coordination salts [Fe(qsal)][Ni(dmit)] and [Fe(qsal)](TCNQ)from x-ray absorption (XAS) spectroscopy at the Fe 2pcore threshold. Based on the circularly polarized XAS data, the x-ray natural circular dichroism for [Fe(qsal)][Ni(dmit)] and [Fe(qsal)](TCNQ)is far stronger than seen for [Fe(qsal)]Cl suggesting this natural circular dichroism signature is a ligand effect rather than a result of just a loss of octahedral symmetry on the Fe core. The larger the chiral effects in the Fe 2p core to bound XAS, the greater the perturbation of the Fe 2pto 2pspin-orbit splitting seen in the XAS spectra.

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.

Coordination Chemistry of Uranyl Ions with Surface-Immobilized Peptides: An XPS Study.

The coordination chemistry of uranyl ions with surface immobilized peptides was studied using X-ray photoemission spectroscopy (XPS). All the peptides in the study were modified using a six-carbon alkanethiol as a linker on a gold substrate with methylene blue as the redox label. The X-ray photoemission spectra reveal that each modified peptide interacts differently with the uranyl ion.

Voltage controlled bio-organic inverse phototransistor.

Thin films of poly-d-lysine act as polar organic and are also light sensitive. The capacitance-voltage, current-voltage, and transistor behavior were studied to gauge the photoresponse of possible poly-d-lysine thin film devices both with and without methylene blue as an additive. Transistors fabricated from poly-d-lysine act as inverse phototransistors, i.

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)].

Evidence for surface effects on the intermolecular interactions in Fe(II) spin crossover coordination polymers.

From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS), it is evident that the spin state transition behavior of Fe(II) spin crossover coordination polymer crystallites at the surface differs from the bulk. A comparison of four different coordination polymers reveals that the observed surface properties may differ from bulk for a variety of reasons. There are Fe(II) spin crossover coordination polymers with either almost complete switching of the spin state at the surface or no switching at all.