Unprecedented Binary Semiconductors Based on TCNQ: Single-Crystal X-ray Studies and Physical Properties of Cu(TCNQX2) X= Cl, Br

Single crystals of a new structure type for the M+(TCNQ)(center dot-) binary family are isolated from reactions of dihalogenated TCNQ derivatives and Cu-I ions (see figure; Cu: pink C: black, N: blue, Br: orange, H: light blue). The new compound Cu(TCNQCl(2)) exhibits the highest conductivity of the M+(TCNQ)(center dot-) series to date, despite the larger separation of TCNQCl(2) units in the stacks. Conductive properties of Cu(TCNQX(2)) where X=Cl, Br is attributed to charge-carrier transport through copper ions, which is unprecedented in M+(TCNQ)(center dot-) materials.