| Abstract: | The PhD dissertation is devoted to selected problems of the IR spectral properties of
hydrogen bonds stabilizing the crystal lattices of model crystals of dicarboxylic acids, with the
particular attention paid to the aromatic molecular systems. The investigation results collected by
systematic spectral studies of diverse succinic acid isotopomer crystals allowed for the
identification of a novel generation mechanism of the inter-hydrogen bond interactions in molecular
crystals, namely of the so-called “long-distance” dynamical co-operative interactions. Intensive
studies of molecular crystals of the isomeric benzenedicarboxylic acids (i.e. terephthalic, phthalic
and isophthalic acid), with their lattices containing infinitely long chains of the molecules linked
together by hydrogen bonds, coupled together by the π-electronic aromatic ring systems, prove that
in these cases extremely strong co-operative interactions involving the distant hydrogen bond cycles
take place. In terms of the proposed theoretical model of the “long-range” dynamical co-operative
interactions in a “superdimer” of hydrogen bonds it was possible to interpret non-conventional H/D
isotopic effects, depending of a non-random distribution of the protons and deuterons not only in
the hydrogen bond cycles but also in longer associate molecule chain fragments. On the basis of the
“superdimer” model the effect of the deuterium distribution in the terephthalic acid molecules on to
rates of the H/D isotopic exchange in the crystalline hydrogen bonds was explained. The extremely
high melting point as well as the extremely low solubility of terepthalic crystals may by also
explained on the basis of the model. The theoretical model was also experimentally verified via
spectral studies of crystals of mono- and polycyclic dicarboxylic acid crystals of the alicyclic and
the alkilaromatic character.
IR spectroscopic studies of crystals of seven isomeric naphthalene dicarboxylic acids have
shown that the dynamical co-operative interactions of the “long-range” are not the sole factor
determining the H/D isotopic exchange rates. The extremely high passivity of the “ 1,3” and “ 1,6”
isomers was ascribed to a high energy barrier for the H/D isotopic exchange reaction due to the
necessity of the dearomatization of the aromatic rings in the transition states of the reaction in these
cases.
The role of the symmetry as the factor determining the susceptibility of the other five
isomeric systems (i.e. of the “ 1,4”, “2,3”, “ 1,5”, “2,6” and “ 1,7” naphhthalene dicarboxylic acids)
on to the H/D isotopic exchange depends on the strong modification of the “long-range” dynamical
co-operative interaction energy magnitudes, as the result of the differences in the π-electron density
distribution in the naphthalene ring α and β positions. The relative distances between the carboxyl
groups, due their substitution on one or in two different six-membered cycles also determine the
H/D isotopic exchange rates in the naphthalene dicarboxylic acid isomers. |