One-Dimensional π-Stacks of Pancake-Bonded 5,6-Dichloro-2,3-dicyanosemiquinone Radical Anions ?

A series of six novel salts of 5,6-dichloro-2,3-dicyanosemiquinone (DDQ) radical anions with aromatic cations is studied by structural characterization, magnet-ization, and conductivity measurements. Different types of stacking of DDQ radicals, which determine electrical and magnetic properties, are observed: regular stacks of equidistant radicals (resulting in semiconductivity along the direction of stacking), stacks of pancake-bonded dimers, isolated pancake-bonded dimers, and mixed stacks comprising DDQ radicals and aromatic cations. General features of pancake bonding of DDQ radicals are defined: parallel ring planes, offset along the carbonyl center dot center dot center dot carbonyl axis by 2.05-2.15 angstrom, and interplanar separations of 2.90-2.95 angstrom (for pancake-bonded dimers) or 3.08-3.24 angstrom (for regular stacks of equidistant radicals).

Automated summary

This study investigates a series of six novel salts formed by aromatic cations and 5,6-dichloro-2,3-dicyanosemiquinone (DDQ) radical anions through structural characterization, magnetization, and conductivity measurements. Different stacking modes of DDQ radicals and the general features of pancake bonding are observed.