Tuning of the degree of charge transfer and the electronic properties in organic binary compounds by crystal engineering: a perspective

Abstract

Organic charge-transfer compounds have received significant attention because of their tunable electronic properties, ranging from insulators to superconductors. It has been demonstrated that these compounds can be applied to both organic semiconducting active materials and organic conductors by appropriate molecular design. 7,7,8,8-Tetracyanoquinodimethane (TCNQ) and F_xTCNQ (x = 1, 2, 4) as acceptors and aromatic hydrocarbons form a variety of compounds in which the degree of charge transfer (DCT) is adjustable. The donor, acceptor, and stoichiometry of organic charge-transfer compounds are the main factors for tuning the DCT. Tuning of the DCT by crystal engineering allows control of the delocalized electrons and thus the physical properties of materials in a range that is not available in one-component organic solids.