Radical-anion salts have been prepared by electro-Specific interactions between DCNQI anions and dications are absent. The effect on the stacking of the DCNQI units of crystallization from seven 2,3-and 2,5-disubstituted DCNQIs and the quaternary dications (AMM 2+ ) HMED, DMBP, EBP, the two positive charges in the dications which are held apart at a defined separation is discussed. The salts are shown to and EBBT. The black compounds adopt the stoichiometry DCNQI/dication = 3:1. The crystal-structure analysis of two be semiconductors with powder conductivities of 10 Ϫ2 to 10 Ϫ5 S cm Ϫ1 . of these radical salts reveal skewed (zigzag, trimerized) stacks of DCNQI molecules separated by sheets of dications.
N,NЈ-dicyanoquinone diimines (DCNQIs) have been stacks which provide one-dimensional conductivity. The ammonium ions are distributed within holes in the crystal demonstrated to yield a large variety of highly conducting radical-anion salts with monovalent cations of the stoichi-lattice, obviously balancing crystal forces with Coulomb attractions. There are no specific interactions to be seen ometry [DCNQI] 2 M (M ϭ Li, Na, K, NH 4 , Rb, Tl, Cu, Ag). In these salts the nitrile groups of the anions are coor-between anions and cations (examples A , B ,
C ). dinated to the central metal ions forming skewed stacks of the ligands (space group I4 1 /a or closely related). This spe-We therefore set out to tune the crystal packing of the DCNQI units by employing quaternary dications. In this cial arrangement of the DCNQI ligands, however, is restricted to 2,5-disubstituted DCNQIs and cannot be obtained way, the cations cannot simply be placed in the same way as in examples A and B since the second positive charge is with e.g. 2,3-disubstituted DCNQIs. If ammonium ions are employed instead of monovalent separated from the first by a defined distance. These dications therefore impose special crystal structures on their metal ions, DCNQI radical-anion salts of varying stoichiometry are formed with reasonable conductivities (Scheme DCNQI radical-anion salts according to their geometry.
For our experiments we selected the following dications: 1) similar to their TCNQ counterparts. As far as the crystal structures of these DCNQI salts Hexamethyl-1,2-ethane-diammonium ion (HMED), N,NЈdimethyl-4,4Ј-bipyridinium ion (DMBP), N,NЈ-ethylene-are known, the anionic ligands are arranged in zigzag Scheme 1. DCNQI radical-anion salts 1 with monovalent ammonium cations