OXIDATION OF PHOSPHINES CONTAINING 2 OR 3 TETRATHIAFULVALENE (TTF) ORO-DIMETHYL-TTF MOIETIES - EVIDENCE FOR FORMATION OF RADICAL POLYCATIONS

Stepwise oxidation of tetrathiafulvalenyl(diphenyl)phosphine (1), -dim ethyltetrathiafulvalen-4-yl(diphenyl)phosphine (1a), bis(tetrathiafulv alenyl)phenylphosphine (2), ,5'-dimethyltetrathiafulvalen-4-yl)phenylp hosphine (2a), tris(tetrathiafulvalenyl)phosphine (3) and ris(4',5'-di methyltetrathiafulvalen-4-yl)phosphine (3a) was followed by EPR and EN DOR spectroscopy, and cyclic voltammetry. Each of the tetrathiafulvale ne (TTF) or 4,5-dimethyltetrathiafulvalene (o-DMTTF) moieties in 1-3a donates two electrons, so that exhaustive oxidation at potentials belo w 1 V(vs. SCE) leads to the dications 1(2+) or 1a(2+), the tetracation s 2(4+) or 2a(4+) and the hexacations 3(6+) or 3a(6+). In 2, 2a, 3 and 3a, the electrons are removed one-by-one from different TTF or o-DMTT F moieties, In the initially formed radical cations 2(.+), 2a(.+), 3(. +) and 3a(.+), the electron hole is delocalized over all TTF or o-DMTT F moieties, two in 2(.+) or 2a(.+) and three in 3(.+) or 3a(.+). On th e other hand, in paramagnetic species produced by further oxidation an d also giving rise to well defined EPR and ENDOR spectra, the unpaired electron appears on the hyperfine time-scale as localized in only one donor moiety. These species are supposed to be the radical trications 2(.3+) or 2a(.3+) and the radical pentacations 3(.5+) or 3a(.5+) The intermediately occurring dications 2(2+) or 2a(2+) and 3(2+) or 3a(2+) , as well as the tetracations 3(4+) or 3a(4+) should have a triplet gr ound-state, while the trications 3(3+) or 3a(3+) are expected to be qu arter species.