Electronic Conduction in Complexes of Aromatic Hydrocarbons with Iodine

Abstract

Molecular complexes of the aromatic hydrocarbons pyrene and perylene with iodine were found to have an electronic conductivity 10 to 12 orders of magnitude higher than that of the constituent compounds. The specific resistivities measured were 75 and 8 ohm-cm, respectively. The materials behaved like semiconductors and plots of log σ vs 1/T gave activation energies of 0.14 ev and 0.019 ev. No Hall effect could be found, but an upper limit for the mobility of μ≤.01 cm2v—1 sec—1 could be set. Single crystals of the perylene-iodine complex were obtained. The preparation and identification of the complexes are discussed and the results of a phase study on the system of pyrene and iodine are reported.

Molecular iodine/polymer complexes

“…Indeed, some reports indicate the weakness of this inter action [355][356][357]. However, some molecules of about the same ionization potential such as pyrene (7.41 eV) and perlyene (7.00 eV) do act as electrondonors towards molecular iodine [358,359]. The reaction between fuller ene C 60 and molecular iodine was first made by Kobayashi and his collaborators [360].…”

Infinite Polyiodide Chains in the Pyrroloperylene–Iodine Complex: Insights into the Starch–Iodine and Perylene–Iodine Complexes

“…This implies that all the iodine atoms in the polyiodide chain carry a partial negative charge. So far, with very few exceptions, the geometry of polyiodide chains (I 5À , I 7À , and I 9À ) reported in the literature is non-linear, [11] whereas the polyiodide chain found in the pyrroloperylene-iodine complex at 100 K and room temperature is nearly linear. We examined the electrical properties of four single crystals of the complex and found some variation in their electrical behavior attributable to mechanical defects and cracking near the contacts during temperature changes (see the Supporting Information).…”

“…These descriptions of iodide chains, as well as numerous others, are better described as oligomeric rather than polymeric chains of iodine, with lengths typically shorter than 10 iodine units and usually containing molecular iodine within the chain. [9] Indeed, a seminal resonance Raman spectroscopic study of starch iodine carried out in 1978 allowed the authors inferred the presence predominantly I 5À species.[10]A separate and highly relevant structural mystery involving iodine is that of one of the earliest organic electronic conductors; the perylene-iodine charge-transfer complex, [11] which to this day, has not been fully resolved. It is clear that the hydrocarbon is partially oxidized and the iodine shows hints of iodine and triiodide [12] but the latter are disordered in essentially, all examined cases.…”

Inside Back Cover: Infinite Polyiodide Chains in the Pyrroloperylene–Iodine Complex: Insights into the Starch–Iodine and Perylene–Iodine Complexes (Angew. Chem. Int. Ed. 28/2016)

“…This implies that all the iodine atoms in the polyiodide chain carry a partial negative charge. So far, with very few exceptions, the geometry of polyiodide chains (I 5-, I 7-, and I 9-) reported in the literature is non-linear, 11 whereas the polyiodide chain found in the pyrroloperylene-iodine complex at 100 K and room temperature is nearly linear. We examined the electrical properties of four single crystals of the complex and found some variation in their electrical behavior attributable to mechanical defects and cracking near the contacts during temperature changes (see supporting information).…”

“…A separate and highly relevant structural mystery involving iodine is that of one of the earliest organic electronic conductors; the perylene-iodine charge transfer complex, 11 which to this day, has not been fully resolved. It is clear that the hydrocarbon is partially oxidized and the iodine shows hints of iodine and triiodide 12 but the latter are disordered in essentially, all examined cases.…”