(15)N and (13)C high-resolution solid-state NMR study of the polymorphism of the L-enantiomer of N-benzoylphenylalanine.

In this paper, several approaches which allow the investigation of mixtures of polymorphs, employing modern solid-state NMR (SS NMR) spectroscopy are reported. A convenient methodology for characterization of the hydrogen bonding and molecular conformation of a polymorphic sample by means of one-dimensional and two-dimensional, 13C and 15N NMR experiments as well as CSA tensor analysis and theoretical calculations is presented. Two-dimensional heteronuclear SS NMR allowed definition of the polymorphic domain of N-benzoyl-L-phenylalanine (N-Bz-Phe). The graphical method of Herzfeld and Berger was used to measure the 13C and 15N spinning sideband intensities which allowed the calculation of NMR parameters for labeled centers of N-Bz-Phe. The experimental data were compared with computed results obtained by means of the DFT hybrid method with B3PW91 functional and 6-311++G** basis set.

Search of nature of planar chirality for pendent benzodiazacoronands in the solid state: NMR, X-ray, and DFT studies.

In this work, we report the structural studies on the solid state of two benzodiazacoronads that form chiral and achiral crystals. Crystals have to be considered as a two-component system consisting of an organic unit and a water molecule in 1:1 ratio. Both components play an important role in the crystal structure. The strong (O-H...O, N-H...O) and weak (C-H...O) intermolecular hydrogen bonds are responsible for phase organization and, in consequence, formation of chiral or achiral crystals. The alignment of the water molecule with respect to the macrocycle is different for samples 1 and 2. Removal of water from the crystal lattice of 1 is reversible. Formation of chiral cocrystals from two different achiral molecules by self-assembly is well-known. However, in this paper, we show that the water molecule can be an important achiral cofactor responsible for chiral crystallization.

Structure and dynamics of L-selenomethionine in the solid state.

L-selenomethionine 1 crystallizes in P2(1) space group with two molecules in the asymmetric unit. Solid-state NMR spectroscopy is used for searching of structure and dynamics of 1 in the crystal lattice. The distinct molecular motion of side chains for A and B molecules of 1 is apparent from measurements of relaxation parameters (1H 1rho, 13C T1) and analysis of CSA data (2D-PASS experiment). The 13C delta(ii) and 77Se delta(ii) parameters are correlated with theoretical shielding parameters obtained by means DFT GIAO calculations. Attempt to explain the mechanism of phase transition of crystals of 1 at 313K is presented.