Toward the Single-Molecule Investigation of Organometallic Reaction Mechanisms: Single-Molecule Imaging of Fluorophore-Tagged Palladium(II) Complexes

Abstract

The single-molecule fluorescence microscopy imaging of indiVidual palladium(II) complexes is reported and the requisite high-quantum-yield BODIPY fluorophore tags are synthesized and shown to act as spectators when bound to metal complexes. These combined experimental results lay the fundamental groundwork for studying organometallic reaction chemistry at the single-molecule leVel using fluorophore tags.

How Important Is the Release–Return Mechanism in Olefin Metathesis?

“…[9] We and others recently discovered that tagging of ligands in metal complexes with fluorescent dyes can provide useful information on ligand dissociation reactions due to changes in the fluorescence intensity during the catalytic reactions. [10] Transition-metal ions often quench the fluorescence of such dyes and consequently fluorophore-tagged ligands coordinated to such metals, render weakly fluorescent complexes. [11] However, upon dissociation of the tagged ligand from a metal complex, the fluorescence is restored due to the spatial separation between the two components.…”

Copper nanoparticle heterogeneous catalytic ‘click’ cycloaddition confirmed by single-molecule spectroscopy

“…The preferred signalling processes are those that activate emission from a dye or shift its emission wavelength. Chemical reactions studied with single-molecule microscopy can be separated into two categories: those that change the structure of a molecule altering its emission properties 31 and those that require a tag such as an attached dye to probe the reaction 43 ; the dyes in these two categories have been termed participants and spectators, respectively 38 . The CuAAC click reaction falls into the second category since azide and alkyne reactive groups do not emit and an attached dye is required to visualize the reaction.…”

Location change method for imaging chemical reactivity and catalysis with single-molecule and -particle fluorescence microscopy

“…With a freely diffusing product approach, care must be taken to assign this disappearance with chemical change rather than other processes such as quenching or photobleaching that would also cause disappearance of the signal from the originally tethered molecule. Physical or chemical attachment of only the product and not the starting material to the glass 5,6,[18][19][20][21] or changes in local viscosity within a reaction medium 7 have been employed to achieve this difference in diffusion rate.…”

“…[1][2][3][4] As in operando detection with fluorescence microscopy reaches the ultimate sensitivity limit of individual molecules and particles-and now of individual chemical reactions-an increasing number of chemists are designing experiments to gardener unique insights into catalysis and stoichiometric reactivity via this technique. Identification of the active phase of the catalyst in rutheniumcatalyzed polymerization, 5 mechanisms responsible for polymer morphology, 6 local environments in radical polymerization, 7,8 crystal face selectivity in surface hydrolysis of esters, 9 mechanistic steps in epoxidation of olefins, 10,11 heterogeneous reactivity of gold nanocatalysts, [12][13][14][15][16] protonation of amines, 17 surface spatial distribution with kinetics of ligand exchange reactions at platinum, [18][19][20][21][22] and ordering within nanomaterials 23 have provided the first applications in purely chemical systems unrelated to biology. 24 In order to image a chemical process, however, this chemical process needs to result in a change in fluorescent output that is detectable.…”