Electric Conductivities of Partially Oxidized Organometallic 1D Systems
It had been mentioned that a partial charge transfer is often a necessary condition in organometallic solids to observe high electric conductivities. Detailed experimental investigations of the temperature-dependence of single crystal conductivities are available for metallomacrocycles that crystallize in columnar structures of type I (see section II.1). The subsequent analysis is thus restricted to the conductivities (σ) of these 1D materials. The largest (room temperature) conductivities in this class of compounds are of the order of 2·103 (Ωcm)−1. The maximum conductivities in organometallic solids of type III or IV are ca. 10−4 to 10−3 (Ωcm)−1. The temperature dependence of σ in the latter 1D systems corresponds to a semiconducting behavior. The outline of this section is as follows; the temperature-dependence of the single-crystal conductivity is discussed for representative model systems. Furthermore we give a short comparison of charge carrier parameters (i.e. mean free paths) of organometallic systems with quantities derived for organic metals and “inorganic” 1D conductors (i.e. Krogmann’s salt). Only simple phenomenological relations and qualitative interpretations are employed to classify experimental findings. At the end of this section microscopic approaches to the conductivity problem are shortly mentioned; these schemes go beyond widely used semiphenomenological descriptions.
KeywordsIodide Macrocycle TCNQ Tetrathiafulvalene Tetracyanoquinodimethane
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