Electron Paramagnetic Resonance (EPR) Data of 1D Organometallic Solids of Class I
The identification of the nature of the charge carriers in organometallic solids with macrocyclic ligands was an unresolved problem until the late seventies where it was conventionally (frequently) accepted that partial oxidation processes are metal-centered. But this assignment was misguided and lead to the incorrect assumption that metal-metal contacts in columnar structures should be a prerequisite for highly conducting modifications of suitable 1D materials. Subsequent experimental investigations of organometallic solids, that crystallize in the columnar structure of class I, have shown that most of the systems are organic metals with channels for the charge transfer that are provided by the (cyclic) organic ligands. This experimental result was corroborated by (semiempirical) tight-binding calculations which are discussed in section IV. The identification of the transfer channels was possible by several experimental techniques. In the first place one has to mention electron paramagnetic resonance (EPR) spectra where the measured g values have been used to discriminate between organic π radicals and partially oxidized transition-metal centers. Synthetic strategies (i.e. variations in the composition of the stoichiometric units) allowed for empirical assignments. Substitutions of the central nd site (e.g. Ni→Pd→Pt) in a large number of metallomacrocycles were not accompanied by larger changes in the conductivities; i.e, the transfer channels are independent of the nd center.
KeywordsElectron Paramagnetic Resonance Electron Paramagnetic Resonance Spectrum Macrocyclic Ligand Transfer Channel Electron Paramagnetic Resonance Data
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