Molecular assembly is cruel for improving our understanding of biological world and creating novel functional materials. How to realize controllable molecular assemblies is still challenging, and requires more propounding insights into the mechanism of assembly process, both thermodynamic and kinetic. However, the structures and components of assemblies are quite complex, which make their kinetic process extremely difficult to characterize using traditional NMR techniques.
We collaborated with Prof. Marcel Utz from the University of Southampton and using microfluidic-NMR spectroscopy to study the kinetics in molecular assembly. Kinetics of a multicomponent host-guest supramolecular system containing viologen derivatives, β-cyclodextrins and cucurbiturils were studied by a PMMA based microfluidic chip combined with a dedicated transmission line probe for NMR detection.
By combining microfluidic technology with NMR spectroscopy, the amount of material required for a full kinetic study could be minimized. This is crucial in supramolecular chemistry, which often involves highly sophisticated and synthetically costly building blocks. The small size of the microfluidic structure is crucial in bringing the time scale for kinetic monitoring down to seconds. At the same time, the transmission line NMR probe provides sufficient sensitivity to work at low (2 mM) concentrations.
Fang, H.; Sun, Y.; Wang, X.; Sharma, M.; Chen, Z.; Cao, X.; Utz, M.; Tian, Z., Probing the kinetics in supramolecular chemistry and molecular assembly by microfluidic-NMR spectroscopy. Science China Chemistry 2018, 61 (11), 1460-1464.