News - Suivi du processus de cristallisation en milieu confiné par RMN hyperpolarisée

Suivi du processus de cristallisation en milieu confiné par RMN hyperpolarisée

Des chercheurs des équipes SACS et CMO ont démontré que la RMN à l’état solide, combinée à la polarisation nucléaire dynamique (DNP), permet de révéler la formation d’espèces métastables transitoires (e.g. espèces de nucléation et pré-nucléation) durant les premières étapes de cristallisation de la glycine en milieu nano-confiné. L’approche repose sur l’utilisation d’une nouvelle classe d’agents polarisants constitués de silices mésoporeuses contenant des radicaux TEMPO dans les murs du matériau, développés à l’ICR. Les résultats montrés ouvrent de nouvelles perspectives sur la possibilité de dévoiler l’aspect mécanistique de la nucléation au niveau atomique.

Monitoring Crystallization Processes in Confined Porous Materials by Dynamic Nuclear Polarization Solid-State Nuclear Magnetic Resonance

Marie Juramy, Romain Chevre, Paolo Cerreia Vioglio, Fabio Ziarelli, Eric Besson, Stephane Gastaldi, Stephane Viel, Pierre Thureau, Kenneth D. M. Harris, Giulia Mollica,
Journal of the American Chemical Society, 143 6095-6103 (2021)

Establishing mechanistic understanding of crystallization processes at the molecular level is challenging, as it requires both the detection of transient solid phases and monitoring the evolution of both liquid and solid phases as a function of time. Here, we demonstrate the application of dynamic nuclear polarization (DNP) enhanced NMR spectroscopy to study crystallization under nanoscopic confinement, revealing a viable approach to interrogate different stages of crystallization processes. We focus on crystallization of glycine within the nanometric pores (7-8 nm) of a tailored mesoporous SBA-15 silica material with wall-embedded TEMPO radicals. The results show that the early stages of crystallization, characterized by the transition from the solution phase to the first crystalline phase, are straightforwardly observed using this experimental strategy. Importantly, the NMR sensitivity enhancement provided by DNP allows the detection of intermediate phases that would not be observable using standard solid-state NMR experiments. Our results also show that the metastable beta polymorph of glycine, which has only transient existence under bulk crystallization conditions, remains trapped within the pores of the mesoporous SBA-15 silica material for more than 200 days.

Establishing mechanistic understanding of crystallization processes at the molecular level is challenging, as it requires both the detection of transient solid phases and monitoring the evolution of both liquid and solid phases as a function of time. Here, we demonstrate the application of dynamic nuclear polarization (DNP) enhanced NMR spectroscopy to study crystallization under nanoscopic confinement, revealing a viable approach to interrogate different stages of crystallization processes. We focus on crystallization of glycine within the nanometric pores (7−8 nm) of a tailored mesoporous SBA-15 silica material with wall-embedded TEMPO radicals. The results show that the early stages of crystallization, characterized by the transition from the solution phase to the first crystalline phase, are straightforwardly observed using this experimental strategy. Importantly, the NMR sensitivity enhancement provided by DNP allows the detection of intermediate phases that would not be observable using standard solid-state NMR experiments. Our results also show that the metastable β polymorph of glycine, which has only transient existence under bulk crystallization conditions, remains trapped within the pores of the mesoporous SBA-15 silica material for more than 200 days.

Collaboration : Prof. Kenneth D.M. Harris, University of Cardiff (UK)

Fundings :

– ERC StG « STRUCTURE » GA 758498

– A*MIDEX Programme “Investissements d’Avenir” (Grant ANR-11-IDEX-0001-02)