A Truly Isolated TCNQ~(·-) Dimer?

摘要

The nature of the countercation is a major factor in determining solid-state architectures and properties of 7,7′,8,8′-tetracyano-p-quinodimethane (TCNQ) salts. A number of different types of ion pair association are observed with organic cations, but in the case of metal ion salts cation interaction with the nitrogen lone pairs dominates though the TCNQ radical anion (TCNQ~(·-)) is still sometimes regarded as a relatively poor ligand. Ionophore encapsulation of a cation provides a potentially versatile means of constraining and controlling ion-pair association, particularly in the solid state. For example, while extended TCNQ~(·-) stacks are found in KTCNQ and RbTCNQ, the solid-state structures of their 18-crown-6 complexes 1 and 2 reveal brickwork lattices of dimers.