Dye synthesis in the Pechmann reaction: catalytic behaviour of samarium oxide nanoparticles studied using single molecule fluorescence microscopy

2018

Angew Chem Int Ed

Catalytic cycles are typically depicted as possessing time-invariant steps with fixed rates. Yet the true behavior of individual catalysts with respect to time is unknown, hidden by the ensemble averaging inherent to bulk measurements. Evidence is presented for variable chemical kinetics at individual catalysts, with a focus on ring-opening metathesis polymerization catalyzed by the second-generation Grubbs' ruthenium catalyst. Fluorescence microscopy is used to probe the chemical kinetics of the reaction because the technique possesses sufficient sensitivity for the detection of single chemical reactions. Insertion reactions in submicron regions likely occur at groups of many (not single) catalysts, yet not so many that their unique kinetic behavior is ensemble averaged.

Section: Figurementioning

confidence: 99%

Evidence for Dynamic Chemical Kinetics at Individual Molecular Ruthenium Catalysts

Easter

2018

Angew Chem Int Ed

“…Catalysis is aworldwide multibillion-dollar industry,but the determination of the phase and local environment of active catalysts is al ong-standing analytical challenge. [1,2] This is especially true in reactions at the homogeneous/heterogeneous interface where the (unknown) phase and locations of the active catalyst can have ap rofound effect on its local environment and, thus,its reactivity and selectivity.Herein we employed fluorescence microscopy to monitor single monomer insertion reactions at individual molecular catalysts under synthetically relevant conditions.The resultant imaging data revealed phase- [3,4] and spatiotemporally resolved individual active molecular ruthenium catalysts within growing polymers for the first time,t hereby providing information that is unavailable through traditional ensemble techniques. Thei ndustrially important [5] monomer norbornene and catalyst 1 were selected for initial studies.C atalyst 1 is inactive when phosphine is coordinated; [6] thus,t he presence of ruthenium does not imply catalytic activity.…”

mentioning

confidence: 99%

Single Turnover at Molecular Polymerization Catalysts Reveals Spatiotemporally Resolved Reactions

Easter¹,

2017

Angew Chem Int Ed

Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single-turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components.

“…Although well‐known in biological systems, zeolites, and nanoparticle catalysis, this is the first example where single‐molecule fluorescence microscopy has been used to visualize single‐turnover events with a molecular catalyst . Given that molecular catalysts make up a significant portion of all catalysis, imaging turnover in these systems at the single‐molecule level holds great potential to reveal information on reactivity hidden by ensemble averaging, similar to what has been achieved with biological, zeolite, and nanoparticle systems …”

Section: Figurementioning

confidence: 85%

Single Turnover at Molecular Polymerization Catalysts Reveals Spatiotemporally Resolved Reactions

Easter¹,

2017

Angewandte Chemie

Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single‐turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring‐opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components.