It
was found that the dicarbonyl-rhodium-
o
-semiquinonate
complex (which thread-like crystals can bend reversibly under light/warm
activation) can form two polymorphic modifications: isometric prisms
(
1
) and sticks (
2
). Some thin sticks can
bend as mentioned above. X-ray diffraction studies of polymorphic
modifications at different temperatures were carried out. It was found
that crystals
1
are destructed after cooling to 110 K
as opposed to crystals
2
. In turn, the reversible phase
transition is detected in
2
. In both polymorphic modifications,
stack packaging motifs through the direct Rh–Rh bond are observed.
The principal difference between packages of polymorphic modifications
is that molecules
1
in the adjacent stacks are shifted
relative to each other along the stack, in contrast to crystal
2
. It was found that different packing of stacks leads to
different anisotropic compression of crystals
1
and
2
during cooling, which is a key factor of their stability.
Using the molecular invariom approach, the nature of the chemical
bonds and charge distribution was investigated; the energy of the
Rh–Rh bonds was estimated.