NMR diffusion spectroscopy for the characterization of multicomponent hydrogen-bonded assemblies in solution

Abstract

NMR diffusion measurements on 10 different multicomponent hydrogen-bonded assemblies, viz. the three single rosettes SR1-SR3 (1 3 ؒ2a 3 , 1 3 ؒ2b 3 , 1 3 ؒ2c 3 ) the double rosettes DR1-DR5 (3a 3 ؒ2a 6 , 3b 3 ؒ2b 6 , 3c 3 ؒ2a 6 , 3d 3 ؒ2a 6 , 3e 3 ؒ2a 6 ), and DR6 (4a 3 ؒ1 6 ), and the tetrarosette TR (5 3 ؒ2a 12 ) are described. Some of the above rosettes have been previously identified as well-defined assemblies (viz. SR1, DR1-DR3, and TR) using established characterization techniques ( 1 H NMR spectroscopy, X-ray diffraction, and MALDI-TOF MS after Ag ϩ -labeling). The diffusion coefficients of these assemblies were studied and used as a reference for the identification of three new assemblies (DR4-DR6), the characterization of which could not be established unequivocally using other characterization tools. A good correlation was found between the experimental and calculated diffusion coefficients when DR1 was used as a reference. A relatively good correlation was obtained between the effective hydrolytic radii calculated from the diffusion data and those extracted from gas phase-minimized structures with SR1 and DR2 being exceptions. The diffusion measurements show that assembly DR4 is a thermodynamically stable species, while assemblies DR5 and DR6 are less stable and only present to a minor extent.

Unraveling the nanostructure of supramolecular assemblies of hydrogen-bonded rosettes on graphite: An atomic force microscopy study

“…Considering the known crystal structure of the corresponding double rosette assemblies (21) and the gas phase minimized structure of the tetrarosettes (see Scheme 1; ref. 22), the observed nanorods can be concluded to consist of rows of tetrarosette assemblies. Based on the gas phase minimized structure, the area requirement for such an arrangement is Ϸ8.6-9.9 nm 2 , depending on the orientation.…”

Diffusion NMR Spectroscopy in Supramolecular and Combinatorial Chemistry: An Old Parameter—New Insights

“…[84,85] The pulsed gradient spin echo (PGSE) sequence was used to characterize several rosettes prepared by the research group of Reinhoudt. [86] In this study, single, double, and tetrarosettes of the type shown in Scheme 1 were classified on the basis of their diffusion coefficients. [86] Relatively good agreement was found between the hydrodynamic diameter extracted from diffusion NMR measurements and those obtained from gas-phase-minimized structures.…”

Reprogramming the assembly of unmodified DNA with a small molecule

“…Furthermore, diffusion ordered NMR spectroscopy (DOSY) of an analogous mixture showed the formation of a single slow diffusing species, rather than a mixture of oligomers with different diffusion coefficients. Using the diffusion coefficient of monomeric TIPDS--dA and its molecular weight as references, a molecular weight range for the species in the mixture can be estimated and is consistent with a hexameric rosette 48 .…”