Ring-strain-modified properties of substituted perylene radical cation salts. A solid-state carbon-13 CPMAS NMR study

Abstract

The authors have considered the stereochemical distortions of the molecular building blocks as a way to control the structure to properties relationships of organic conductive solids. 1,2,7,8-Tetrahydrodicyclopenta (cd,lm)perylene (CPP) and 3,4,9,10-tetramethylperylene (TMP), bearing sterically hindered substituents that involve strain-induced distortions of the perylene skeleton, have been synthesized. Two conductive radical-cation salts, CPP{sub 2}PF{sub 6}{center dot}CH{sub 2}Cl{sub 2} and TMP{sub 2}PF{sub 6}{center dot}CH{sub 2}Cl{sub 2}, have been prepared from these two strained donors by galvanostatic electrocrystallizations at {minus}20C in CH{sub 2}Cl{sub 2}. These two salts are isostructural (monoclinic, space group C{sub 2/m}). The structures consist of similar regular stacks of the almost planar donors (the bond lengths and angle values being distorted as expected) along the crystallographic c axis. The refinements of the structures have been difficult because of the disorder of the counterions and of the solvent contained in the channels between the organic stacks. Solid-state {sup 13}C CPMAS NMR, has been used to study both salts. They exhibit two different locally resolved {sup 13}C conduction electron Knight shift sets.