Structure and Dynamics of the Host-Guest Complex of a Molecular Tweezer: Coupling Synthesis, Solid-State NMR, and Quantum-Chemical Calculations

Abstract

Together they are strong. The combination of fast MAS solid‐state NMR experiments and ab initio calculations on 1H chemical shifts allows the resolution and assignment of guest and host protons in a supramolecular complex (as shown here), provides information about motional processes, and identifies the specifics of intra‐ and intercomplex interactions.

Quantum-chemical simulation of solid-state NMR spectra: the example of a molecular tweezer host–guest complex

“…Structures of the solid-state fragments of the dicyanobenzene-tweezer complex were obtained by optimizing the monomer at the HF/6-31G* level with constraints from the X-ray structure [10] and subsequently projecting the monomer units onto the experimentally maintained positions in the solid-state [12]. SCF calculations were carried out employing linear-scaling F o r P e e r R e v i e w O n l y methods for calculating the Fock matrix: continuous fast multipole method (CFMM) [13] and linear exchange (LinK) method [14,15].…”

“…By means of our linear-scaling gaugeincluding atomic-orbital Hartree-Fock (GIAO-HF) and GIAO-density functional theory (GIAO-DFT) methods [7,8], we are for the first time able to systematically increase the fragment size of the solid-state structure and to account for all the neighboring complexes of a chosen host-guest complex. Here, we focus on a molecular tweezer system synthesized in the Klärner group [10] which binds a dicyanobenzene guest molecule and can be employed as useful model system for molecular recognition processes. Since an X-ray structure is available for this system [10], it is ideally suited for studying the possibilities of assigning NMR spectra by means of quantum-chemical approaches.…”

“…Here, we focus on a molecular tweezer system synthesized in the Klärner group [10] which binds a dicyanobenzene guest molecule and can be employed as useful model system for molecular recognition processes. Since an X-ray structure is available for this system [10], it is ideally suited for studying the possibilities of assigning NMR spectra by means of quantum-chemical approaches. In order to account for the full neighboring sphere of a host-guest complex, we consider as largest fragment a system with 1196 atoms and 13260 basis functions without molecular symmetry.…”

Powder crystallography of pharmaceutical materials by combined crystal structure prediction and solid-state 1H NMR spectroscopy

“…For small molecules, however, an approach based on the analysis of chemical shifts would be most attractive. There are today many examples of chemical shifts being combined with density functional theory (DFT) calculations for structure validation in organic molecular compounds with respect to known structures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] . However, there are very few examples of ab initio structure determination from powders by NMR without a structural hypothesis.…”

Origins of linewidth in H1 magic-angle spinning NMR

“…2 This resolution is sufficient, for example, to identify correlation peaks due to proton-proton proximities in two-dimensional 1 H double-quantum ͑DQ͒ MAS spectra, with applications including probing hydrogen bonding in self-assembled polymeric structures, 3 pharmaceutical systems, 4 small biomolecules 5 and inorganic complexes, 6 as well as the role of aromatic -interactions in determining packing 7,8 and host-guest interactions for a molecular tweezer. 9 Understanding the factors that determine 1 H resolution in solid-state NMR is key to further applications of 1 H NMR to new structural problems.…”