Friday 22 June 2018, at 15:00, Professor Klaus Merz (Bochum University) will hold a seminar entitled: "Crystal Engineering - using H/D exchange for molecular rearrangement". The seminar is based on the collaboration between the Bochum University and CRS4.
The seminar will be held at room D130, CRS4, Science and Technology Park (Pula, Cagliari, Italy).
More info: Detlef W.M. Hofmann: hofmann@crs4.it
Abstract
For his discovery of "heavy hydrogen" the Nobel Prize was granted to Harold C. Urey in 1934. Followed by the synthesis of heavy water and after the availability of noteable amounts of D2O, deuterated compounds became an increasingly interesting topic of fundamental research and applications. H/D-exchange as the smallest possible element substitution in the molecular structure affects the physical properties that depend directly on the proton or deuterium. Spectroscopic and spin-dependent properties change in a rather predictable way and allow the use of vibrational, NMR and neutron spectroscopies. However, the influence of H/D exchange on thermodynamic properties of compounds is not yet properly understood which is nicely shown in the case of the simple compounds H2O and D2O. Since the discovery of D2 and D2O a large number of deuterated compounds have been prepared and the crystal structures of several of these compounds were investigated. In general, it is expected that the crystal structures of compounds containing hydrogen are not affected by the substitution of hydrogen by deuterium. A detailed survey of deuterated and non-deuterated compounds indicates that the assumption is wrong. Isotopic substitution can influence the molecular arrangement in the solid state. The aggregation of molecules in the solid state is very sensitive to small changes within the substitution pattern of the molecules. Deuterium substitution as a weak directing substituent may have quite an influence on the molecular arrangement. This phenomenon, called isotopic polymorphism, is not only restricted to compounds with absence of strong specific intermolecular interactions in crystal structures. H/D-exchange can influence hydrogen bonds, and as result the crystal structure. Particularly striking is the fact that an isotopic effect can also be observed in the use of solvents in crystallization procedures. Deuterated solvents can control the formation of polymorphic forms in selected cases of small organic compounds.
References:
V. Vasylyeva, T. Kedziorski, N. Metzler-Nolte, C. Schauerte, K. Merz, Crystal Growth & Design, 2010; 10, 4224
K. Merz, V. Vasylyeva, CrystEngCom. 2010; 12, 3989
A. Kupka, V. Vasylyeva, D. W. M. Hofmann, K. Merz, Cryst Growth Des, 2012, 12, 5966
O. V. Shishkin, S. V. Shishkina, A. V. Maleev, R. Zubatyuk, V. Vasylyeva, K. Merz, ChemPhysChem, 2013, 14, 847
K. Merz, A. Kupka, Cryst Growth Des, 2015, 15, 1553
D. D. Enkelmann, D. W. M. Hofmann, K. Merz, Cryst. Growth Des 2017, 17, 4726
J. Falk, D. W. M. Hofmann, K. Merz, IUCrJ, 2018 (submitted)