Solid-state NMR studies of weak interactions in supramolecular systems

Abstract

The field of application of solid-state NMR to the study of supramolecular systems is growing rapidly, with many research groups involved in the development of techniques for the study of crystalline and amorphous phases. This Feature Article aims to provide an overview of the recent contributions of our research group to this field, paying particular attention to the study of the weak interactions such as hydrogen bonds in supramolecular systems through solid-state NMR investigations. The structure and dynamic behaviour of selected host-guest systems will be also discussed.

Enhanced Oral Bioavailability of Vinpocetine Through Mechanochemical Salt Formation: Physico-Chemical Characterization and In Vivo Studies

“…Indeed, the 15 N chemical shift is more sensitive to protonation or to the presence of hydrogen bonds than that of other nuclei, such as 1 H and 13 C, due to its wider chemical shift range. Protonations as well as intermolecular hydrogen bonds produce high-or low-frequency shifts in the 15 N values, according to the type of nitrogen atom and to the type of interaction (38). The VIN spectrum was characterized by two resonances at 4.0 and 113.6 ppm for N4 and N1, respectively.…”

Solid‐State NMR Investigation of Ligand Mobility and Reactivity in Transition Metal Complexes

“…[83] Depending on the reaction environment, i.e. in solution or solid-gas, the product can be the monocarbonyl B, the dicarbonyl C or D species, where D has the same stoichiometry as C, but exhibits a different 31 P CPMAS spectrum (Scheme 2, b). As the reaction proceeds it has been observed a progressive decrease of 31 The significant differences in 31 P NMR patterns, the minor stability of D with respect to C as well as the similarity of their IR and DRIFT spectra, strongly suggest that D represents a metastable or activated species (not observable in solution) in which a phosphane arm from NP 3 , although unfastened, is located close to the metal centre as a consequence of the constraining environment of the crystal lattice.…”

“…For instance Pecharsky and co-workers used 31 P MAS NMR, combined with XRPD and DTA, for monitoring the formation of transition metal complexes, [96] phosphonium salts [95] and phosphorus ylides. [97] They (Figure 11).…”

Solid‐State NMR Studies on Supramolecular Chemistry

“…In particular, the proton is increasingly deshielded with increasing the HB strength, which leads to 1 H high frequency shifts far from aliphatic and aromatic signals (Scheme 1). 35 The main feature of this technique is that the magnitude of the shift is directly correlated with the length and the strength of the HB. 36 Moreover, the 1 H chemical shift is very sensitive to the location of the hydrogen atom in these interactions.…”