Fluorescent Dendrimeric Molecular Catalysts Demonstrate Unusual Scaling Behavior at the Single-Molecule Level

Abstract

A series of surface-supported molecular palladium catalysts were synthesized using a dendrimeric attachment motif to incorporate multiple BODIPY fluorophores for single-molecule fluorescence microscopy. An unusual fluorescence intensity scaling law was observed, whereby the addition of multiple fluorophores did not result in a substantial increase in single-molecule brightness. Possible quenching mechanisms are discussed, and simulations of photophysical population dynamics are used to identify singlet–triplet annihilation as the likely origin of the scaling law. This work is a conspicuous example of how the availability of different photophysical kinetic pathways can have substantial influence on molecular design rules, with implications for light-harvesting strategies.

Generalized recovery algorithm for 3D super-resolution microscopy using rotating point spread functions

“…Single-molecule and super-resolution imaging 1 2 3 4 5 have changed our understanding of biological processes 6 7 , dynamics at interfaces 8 9 10 11 12 , and functions of catalysts at the single molecule level 13 14 15 . Molecular motors are now known to move hand-over-hand 5 16 .…”

Optical monitoring of polymerizations in droplets with high temporal dynamic range

“…A method was needed to functionalize the glass surfaces in a way that made them highly hydrophobic to repel the aqueous continuous phase but also lipophilic to immobilize the organic phase droplet. To this end, we functionalized pre-cleaned glass coverslips and all-glass reaction chambers 92 using a solution-phase deposition of perfluorosilane, 1 H ,1 H ,2 H ,2 H -perfluorodecyltriethoxysilane, to afford a hydrophobic and lipophilic fluorinated surface (see ESI † for details). Fluorinated surfaces are valuable as an immobilization technique, 93,94 with applications in molecular catalysis 95 and for immobilization of molecules in microarrays for biological assays.…”

Real-time observation of conformational switching in single conjugated polymer chains

“…However, this strategy is incompatible with organic solvents that denature the protein, and therefore, we explored alternative methods based on the direct covalent attachment of the polymer to the glass surface. A triethoxysilane group was chosen on the basis of its well-known ability to covalently react with quartz and glass substrates ( 23 , 24 ). The incorporation of this functional group at one end of the chain provides CPs with the ability to be directly anchored to the substrate surface while preserving the necessary conformational freedom in the rest of the chain to respond to changes in solvent conditions.…”

“…Significant progress has been made during the last 10 years toward oxygen-tight and solvent-resistant chambers for single-molecule microscopy. For example, Ameloot et al ( 38 ) developed an oxygen-tight brass chamber for studying catalytic cycles in acidic and basic aqueous conditions, Upadhyay et al ( 24 ) developed an all-glass chamber for studying dendrimeric molecular catalysts in organic solvents, and Feng et al ( 39 ) developed a reaction chamber that allowed single-molecule experiments in THF. However, the chambers developed by Ameloot et al ( 38 ) and by Feng et al ( 39 ) were sealed with rubber and Devcon 5-min epoxy, respectively, which do not have excellent resistance to a wide range of organic solvents.…”

“…However, the chambers developed by Ameloot et al ( 38 ) and by Feng et al ( 39 ) were sealed with rubber and Devcon 5-min epoxy, respectively, which do not have excellent resistance to a wide range of organic solvents. In this regard, an all-glass chamber similar to the one developed by Upadhyay et al ( 24 ) presents a good alternative; however, it is not reusable and is time-consuming to build. Thus, a chamber that allows for the active control of solvent flow with excellent resistance to a wide range of organic solvents and is reusable and easy to mount still needs to be developed.…”