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

NMR diffusion measurements on 10 different multicomponent hydrogen-bonded a ssemblies, 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 previo usly identified as well-defined assemblies (viz. SR1, DR1-DR3, and TR) usin g established characterization techniques (H-1 NMR spectroscopy, X-ray diff raction, and MALDI-TOF MS after Ag+-labeling). The diffusion coefficients o f these assemblies were studied and used as a reference for the identificat ion 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 co efficients when DR1 was used as a reference. A relatively good correlation was obtained between the effective hydrolytic radii calculated from the dif fusion data and those extracted from gas phase-minimized structures with SR 1 and DR2 being exceptions. The diffusion measurements show that assembly D R4 is a thermodynamically stable species, while assemblies DR5 and DR6 are less stable and only present to a minor extent.