Structures and electrical conductivities of cation radical salts based on unsymmetrical [Au(III)(C-N)(S-S)] type dithiolate complexes

Abstract Crystals of [Au(ppy)(S-S)] 2 [Q][Solvent] n [ppy −  =  C -deprotonated-2-phenylpyridine(−); S-S = C 8 H 4 S 8 2− : 2-{(4,5-ethylenedithio)-l,3- dithiole-2-ylidene}-l,3-dihtiole-4,5-dithiolate(2−), C 8 H 4 S 6 O 2 2− : 2-{(4,5-ethylenedioxy)-l,3-dithiole-2-ylidene(-l,3-dihtiole-4,5-dithiolate (2−); Q  = PF 6 − , BF 4 − AsF 6 − and TaF 6 − ; solvent = PhCl and PhCN; n  = 0–0.5] type cation radical salts were prepared by constant current electrolysis of benzonitrile or chlorobenzene solutions of unsymmetrical [Au(ppy)(S-S)] type metal complexes with [Bu n 4 N][Q] as electrolyte. These salts exhibit two types of unique columnar structures. The one (S-S = C 8 H 4 S 8 2− , Q = PF 6 − /S-S = C 8 H 4 S 6 O 2 2− , Q = BF 4 − ) contains the two-fold head-to-head stacking of cation radicals while the other (S-S = C 8 H 4 S 8 2− , Q  = AsF 6 − , TaF 6 − ) is based on the stacking of tetramers of cation radicals. [Au(ppy)(C 8 H 4 S 8 )] 2 [PF 6 ] shows semiconductive behavior ( E a  = 0.03 eV) under ambient pressure. Interestingly, it shows metallic behavior under high pressure (>0.8 GPa). To our knowledge, this is the first example of the metallic cation radical salt based on the unsymmetrical metal complex. Other radical cation salts show insulating or semiconducting behavior ( E a  = 0.11–0.15 eV).