X-ray powder diffraction patterns revealed that
1‘,1‘‘‘-diheptyl- and 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium
triiodides
obtained from hexane and from dichloromethane have a layered structure
with longer interlayer distances. 1‘,1‘‘‘-Diheptyl-1,1‘‘-biferrocenium triiodide falls under the category reported
before, while 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodide becomes exception; it shows a valence detrapping
with increasing temperature despite
the longer interlayer series. The difference in the crystal
structure between longer and shorter interlayer distance
series was reflected in the difference of the space group.
1‘,1‘‘‘-Diheptyl-1,1‘‘-biferrocenium triiodide
(C34H46Fe2I3) crystallizes in the monoclinic space
group P21/c with unit cell parameters
a = 27.209(10) Å, b =
9.6480(6) Å, c = 14.042(10) Å, β = 98.572(4)°,
and Z = 4, while 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium
triiodide
(C36H50Fe2I3)
crystallizes in the monoclinic space group
P21/c with a =
20.758(6) Å, b = 9.80(1) Å, c =
37.88(2) Å, β =
90.44(3)°, and Z = 8. Both salts in the
present study have a space group of
P21/c, which is different from
the
shorter interlayer series; 1‘,1‘‘‘-dihexyl- and
1‘,1‘‘‘-didodecyl-1,1‘‘-biferrocenium triiodides have a space group
of
P1̄. The difference in the structure between the
1‘,1‘‘‘-diheptyl derivative and the 1‘,1‘‘‘-dioctyl derivative is
also
discussed. There is a difference in the symmetry of the monocation
between the two salts, while both show the
unsymmetrical triiodide anion. The difference between them makes
the difference of the cation−cation interaction.
The structure of the cations agrees with the result of
57Fe Mössbauer spectroscopy. The
cation−cation interaction
in the stacking is observed in 1‘,1‘‘‘-dioctyl derivative, while such
interaction is disturbed by the adjacent stacking
in 1‘,1‘‘‘-diheptyl derivative.
