T. Akutagawa et al., Crystal structures and optical properties of cation radical salts of a tetrathiafulvalene trisannulated macrocycle, J MAT CHEM, 9(11), 1999, pp. 2737-2742
Cation radical salts of the bis(methylthio)tetrathiafulvalene (DMT-TTF) tri
sannulated macrocycles, [tris(DMT-TTF)]I-3(-) (1) and [tris(DMT-TTF)]IBr2-
(2), were prepared and the crystal structures and polarized reflectance spe
ctra of the salts 1 and 2 were investigated. An isostructural character is
observed for the two salts. The C-3 symmetry of tris(DMT-TTF) bearing three
equivalent DMT-TTF units (A, B, and C) within a molecule is broken through
the formation of cation radical salts. Two DMT-TTF units (B and C) of thre
e equivalent units form an intramolecular dimer structure through the face-
to-face pi-pi overlap, whereas the plane of the A unit is orthogonal to the
dimer plane and isolated from the other units. The intramolecular dimers a
re further dimerized through the intermolecular B-B' interaction, resulting
in a DMT-TTF tetramer unit (C-B-B'-C') within the crystal. The intramolecu
lar bond lengths and polarized reflectance spectra indicate the localizatio
n of a unit charge on the B unit rather than A or C. The charge separated A
(0)-B+-C-0 electronic structure is confirmed.