Direkte Beobachtung alternativer Reaktionswege an einzelnen Molekülen

Abstract

Wir danken der Deutschen Forschungsgemeinschaft (DFG) für finanzielle Unterstützung (EXC81, SFB623), Stephen Hashmi (Universität Heidelberg) für hilfreiche Diskussionen, Volker Huch für die rçntgenkristallographische Charakterisierung sowie Michael Schwering und Dominik Brox, die das Projekt mit ihrem Fachwissen in Mikroskopie unterstützt haben. Hintergrundinformationen zu diesem Beitrag sind im WWW unter

Monofluorination and Trifluoromethylation of BODIPY Dyes for Prolonged Single‐Molecule Detection

“…Both FCS and TIRF imaging experiments clearly revealed improved photostabilities upon monofluorination and the two‐fold insertion of trifluoromethyl groups. For applications of the synthesized dyes in single‐molecule chemistry and in life sciences, options for further modifications including those exploited for immobilization are available for these BODIPYs, due to unsubstituted or only methylated α and β positions . We summarize that modification of the BODIPY core with Selectfluor I and the Ruppert–Prakash reagent was successful and gave higher yields than syntheses based on fluorinated pyrroles.…”

An Immobilised Grubbs 2nd Generation Catalyst for Application in Flow‐Through Devices

“…In conclusion, we have developed an advanced and reproducible synthetic protocol for the permanent immobilisation of Grubbs 2 nd generation catalyst onto the inner surface of reaction channels and provided enhanced insights into the kinetics of flow‐through reaction systems. We can assume that using permanently immobilised ligand systems coated onto the inner surface of fused silica capillaries offers a high potential for kinetic characterisation of catalytic reactions,23 in particular for NHC‐carbene ligands, which require tedious and time‐consuming synthetic steps to prepare sufficient material for classic reaction screening schemes. In our set‐up the free carbene ligand can be easily thermally generated and monitored, and we are able to build bonded catalysts with various metal precursors by on‐column ligand exchange.…”

“…These complexes were dissolved in dimethylpolysiloxane and coated onto the inner surface of micro capillaries by the static method introduced by Grob. We can assume that using permanently immobilised ligand systems coated onto the inner surface of fused silica capillaries offers a high potential for kinetic characterisation of catalytic reactions, [23] in particular for NHC-carbene ligands, which require tedious and time-consuming synthetic steps to prepare sufficient material for classic reaction screening schemes. The determined Gibbs activation energy DG ¼ 6 of catalyst 7b (n = 4) is comparable with the dissolved Grubbs 2 nd generation catalyst ( Table 1).…”

Single Turnover at Molecular Polymerization Catalysts Reveals Spatiotemporally Resolved Reactions

“…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 …”

“…In contrast, we demonstrate a strategy (Figure ) that uses unmodified catalyst 1 , which is widely employed in industrial syntheses of polymers, pharmaceutical candidates, and complex molecules . No tethering to an artificial surface, which may alter its reactivity, is necessary. Instead, the experiments herein harness the changing solubility and large size of growing polymers in a precipitation polymerization reaction to aid in imaging individual active molecular catalysts; such catalysts, derived from 1 , within precipitated polymers were sufficiently stationary for successful imaging of single ring‐opening metathesis polymerization (ROMP) reactions.…”