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New Advances in the One-Dimensional Coordination Polymer Copper(II) Alkanoates Series: Monotropic Polymorphism and Mesomorphism
The polymorphism in the copperĀ(II)
alkanoates, recently discovered
for one member, has been thoroughly studied for the whole series,
from 3 to 16 C atoms. Three polymorphic phases have been found, all
of them sharing the same molecular unit, the <i>paddle-wheel</i>, which grows forming a 1D coordination polymer or <i>catena</i>. The three polymorphs are defined by a different packing of these
catenae and a specific arrangement of the alkyl chains. Ten new crystal
structures of those compounds have been solved by high resolution
powder diffraction and presented in this paper. The polymorphism in
this series has been found to be monotropic and is responsible for
the complex thermal behavior observed. The most characteristic feature,
the endothermicāexothermic effect, has been explained for the
first time in these compounds by a combination of data from differential
scanning calorimetry (in normal and modulated modes), powder X-ray
diffraction and Fourier transform infrared spectroscopy. These techniques,
together with small-angle X-ray scattering and optical microscopy,
were used to analyze the hexagonal columnar discotic liquid crystal
phase of copperĀ(II) alkanoates. Thus, new information has been found
in the packing and stacking of the discs formed by the paddle-wheel
units, also maintained in the mesophase