Topic
Valence (chemistry)
About: Valence (chemistry) is a research topic. Over the lifetime, 24937 publications have been published within this topic receiving 645252 citations. The topic is also known as: valency.
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TL;DR: Electronic spectroscopy indicates the population of midgap states upon air exposure and corroborates intervalence charge transfer between Fe2+ and Fe3+ centers, demonstrating that inducing metal-based mixed valency is a powerful strategy toward realizing high and systematically tunable electrical conductivity in MOFs.
Abstract: Partial oxidation of an iron–tetrazolate metal–organic framework (MOF) upon exposure to ambient atmosphere yields a mixed-valence material with single-crystal conductivities tunable over 5 orders of magnitude and exceeding 1 S/cm, the highest for a three-dimensionally connected MOF. Variable-temperature conductivity measurements reveal a small activation energy of 160 meV. Electronic spectroscopy indicates the population of midgap states upon air exposure and corroborates intervalence charge transfer between Fe2+ and Fe3+ centers. These findings are consistent with low-lying Fe3+ defect states predicted by electronic band structure calculations and demonstrate that inducing metal-based mixed valency is a powerful strategy toward realizing high and systematically tunable electrical conductivity in MOFs.
184 citations
TL;DR: The nature of the approximations involved in the derivation of the Poisson Boltzmann equation of the Debye-Huckel theory is investigated in detail from the standpoint of classical statistical mechanics as mentioned in this paper.
Abstract: The nature of the approximations involved in the derivation of the Poisson‐Boltzmann equation of the Debye‐Huckel theory is investigated in detail from the standpoint of classical statistical mechanics. The validity of the initial Debye approximation, under the restrictions originally imposed upon it, is confirmed. Deviations arising from fluctuation terms and van der Waals forces are roughly estimated. An alternative to the Bjerrum method for the treatment of ions of small size and high valence is outlined.
183 citations
181 citations
TL;DR: In this article, the vibrational spectra of mixed valence systems that contained one carbon monoxide ligand on each triruthenium cluster were used to characterize the infrared spectral band shape.
Abstract: Single-electron reductions of linked triruthenium clusters of the general type Ru3-pyrazine-Ru3 produced mixed valence systems showing spectroscopic characteristics of rapid intramolecular electron transfer. Reflectance infrared spectroelectrochemistry was used to characterize the vibrational spectra of mixed valence systems that contained one carbon monoxide ligand on each Ru3 cluster. Infrared spectra in the CO stretching region showed two resolved, partially coalesced, and coalesced ν(CO) bands for clusters with rate constants for intramolecular electron transfer k e increasing from = 1 × 109 s– 1 up to 5 × 1011 and 9 × 1011s– 1, respectively. These data provide a strong correlation between rates of intramolecular electron transfer and infrared spectral bandshape.
181 citations