Preparation and magnetic properties of a range of metal and organic cation salts of 2,3-dicyano-1,4-naphthoquinone (DCNQ). X-Ray crystal structure of (methyltriphenylphosphonium)1(DCNQ)1(H2O)1 and 2-dicyanomethylene-indan-1,3-dione (DCID). The rearrangement of DCID to DCNQ

Abstract

A series of salts (11) formed by the 2,3-dicyano-1,4-naphthoquinone (DCNQ) radical anion with the following counterions has been studied: (a) lithium, (b) methyltriphenylphosphonium, (c) sodium, (d) tetrabutylammonium, (e) tetraphenylarsonium, (f) rubidium, (g) caesium, (h) copper, (i) nickel, (j) cobalt, (k) zinc, (l) tetrathiafulvalene (TTF), and (m) tetramethyl-TTF. A novel method for the preparation of DCNQ salts (11a–c), (11l), and (11m) is described: this involves isomerisation of 2-dicyanomethyleneindan-1,3-dione (7) which is initiated by one-electron transfer to (7) from iodide ion, from sodium metal, or from TTF and TMTTF. DCNQ salts (11b–1) have been prepared from the lithium-DCNQ salt (11a) by cation exchange. The magnetic properties of a selection of these salts have been studied: salts (11a), (11b), (11e), and (11l) are diamagnetic while salts (11d) and (11h) are paramagnetic. The single crystal X-ray structures of the acceptor molecule 2-dicyanomethyleneindan-1,3-dione (7) and the anion radical salt (11b)·H2O have been determined. The anions of salt (11b)·H2O pack in pairs across a centre of symmetry in the crystal lattice. The TTF and TMTTF salts (11l) and (11m) are both semiconductors, σrt= 1.0 and 4 × 10–3 S cm–1, respectively, whereas salts (11a), (11b), (11d), and (11h) are electrical insulators.