Distance-Dependent Plasmon-Enhanced Singlet Oxygen Production and Emission for Bacterial Inactivation

Herein, we synthesized a series of 10 core–shell silver–silica nanoparticles with a photosensitizer, Rose Bengal, tethered to their surface. Each nanoparticle possesses an identical silver core of about 67 nm, but presents a different silica shell thickness ranging from 5 to 100 nm. These hybrid plasmonic nanoparticles thus afford a plasmonic nanostructure platform with a source of singlet oxygen (¹O₂) at a well-defined distance from the metallic core. Via time-resolved and steady state spectroscopic techniques, we demonstrate the silver core exerts a dual role of enhancing both the production of ¹O₂, through enhanced absorption of light, and its radiative decay, which in turn boosts ¹O₂ phosphorescence emission to a greater extent. Furthermore, we show both the production and emission of ¹O₂ <i>in vitro</i> to be dependent on proximity to the plasmonic nanostructure. Our results clearly exhibit three distinct regimes as the plasmonic nanostructure moves apart from the ¹O₂ source, with a greater enhancement for silica shell thicknesses ranging between 10 and 20 nm. Moreover, these hybrid plasmonic nanoparticles can be delivered to both Gram-positive and Gram-negative bacteria boosting both photoantibacterial activity and detection limit of ¹O₂ in cells

Carboxylate-Assisted Formation of Aryl-Co(III) Masked-Carbenes in Cobalt-Catalyzed C–H Functionalization with Diazo Esters

Herein we describe the synthesis of a family of aryl-Co­(III)-carboxylate complexes and their reactivity with ethyl diazoacetate. Crystallographic, full spectroscopic characterization, and theoretical evidence of unique C-metalated aryl-Co­(III) enolate intermediates is provided, unraveling a carboxylate-assisted formation of aryl-Co­(III) <i>masked-carbenes</i>. Moreover, additional evidence for an unprecedented Co­(III)-mediated intramolecular S_N2-type C–C bond formation in which the carboxylate moiety acts as a relay is disclosed. This novel strategy is key to tame the hot reactivity of a metastable Co­(III)-carbene and elicit C–C coupling products in a productive manner

Carboxylate-Assisted Formation of Aryl-Co(III) Masked-Carbenes in Cobalt-Catalyzed C–H Functionalization with Diazo Esters

Herein we describe the synthesis of a family of aryl-Co­(III)-carboxylate complexes and their reactivity with ethyl diazoacetate. Crystallographic, full spectroscopic characterization, and theoretical evidence of unique C-metalated aryl-Co­(III) enolate intermediates is provided, unraveling a carboxylate-assisted formation of aryl-Co­(III) <i>masked-carbenes</i>. Moreover, additional evidence for an unprecedented Co­(III)-mediated intramolecular S_N2-type C–C bond formation in which the carboxylate moiety acts as a relay is disclosed. This novel strategy is key to tame the hot reactivity of a metastable Co­(III)-carbene and elicit C–C coupling products in a productive manner

Carboxylate-Assisted Formation of Aryl-Co(III) Masked-Carbenes in Cobalt-Catalyzed C–H Functionalization with Diazo Esters

Herein we describe the synthesis of a family of aryl-Co­(III)-carboxylate complexes and their reactivity with ethyl diazoacetate. Crystallographic, full spectroscopic characterization, and theoretical evidence of unique C-metalated aryl-Co­(III) enolate intermediates is provided, unraveling a carboxylate-assisted formation of aryl-Co­(III) <i>masked-carbenes</i>. Moreover, additional evidence for an unprecedented Co­(III)-mediated intramolecular S_N2-type C–C bond formation in which the carboxylate moiety acts as a relay is disclosed. This novel strategy is key to tame the hot reactivity of a metastable Co­(III)-carbene and elicit C–C coupling products in a productive manner

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

The selective annulation reaction of alkynes with substrates containing inert C–H bonds using cobalt as catalyst is currently a topic attracting significant interest. Unfortunately, the mechanism of this transformation is still relatively poorly understood, with little experimental evidence for intermediates, although an organometallic Co­(III) species is generally implicated. Herein, we describe a rare example of the preparation and characterization of benchtop-stable organometallic aryl-Co­(III) compounds (NMR, HRMS, XAS, and XRD) prepared through a C­(sp²)–H activation, using a model macrocyclic arene substrate. Furthermore, we provide crystallographic evidence of an organometallic aryl-Co­(III) intermediate proposed in 8-aminoquinoline-directed Co-catalyzed C–H activation processes. Subsequent insights obtained from the application of our new organometallic aryl-Co­(III) compounds in alkyne annulation reactions are also disclosed. Evidence obtained from the resulting regioselectivity of the annulation reactions and DFT studies indicates that a mechanism involving an organometallic aryl-Co­(III)-alkynyl intermediate species is preferred for terminal alkynes, in contrast to the generally accepted migratory insertion pathway

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

The selective annulation reaction of alkynes with substrates containing inert C–H bonds using cobalt as catalyst is currently a topic attracting significant interest. Unfortunately, the mechanism of this transformation is still relatively poorly understood, with little experimental evidence for intermediates, although an organometallic Co­(III) species is generally implicated. Herein, we describe a rare example of the preparation and characterization of benchtop-stable organometallic aryl-Co­(III) compounds (NMR, HRMS, XAS, and XRD) prepared through a C­(sp²)–H activation, using a model macrocyclic arene substrate. Furthermore, we provide crystallographic evidence of an organometallic aryl-Co­(III) intermediate proposed in 8-aminoquinoline-directed Co-catalyzed C–H activation processes. Subsequent insights obtained from the application of our new organometallic aryl-Co­(III) compounds in alkyne annulation reactions are also disclosed. Evidence obtained from the resulting regioselectivity of the annulation reactions and DFT studies indicates that a mechanism involving an organometallic aryl-Co­(III)-alkynyl intermediate species is preferred for terminal alkynes, in contrast to the generally accepted migratory insertion pathway

Isolation of Key Organometallic Aryl-Co(III) Intermediates in Cobalt-Catalyzed C(sp²)–H Functionalizations and New Insights into Alkyne Annulation Reaction Mechanisms

The selective annulation reaction of alkynes with substrates containing inert C–H bonds using cobalt as catalyst is currently a topic attracting significant interest. Unfortunately, the mechanism of this transformation is still relatively poorly understood, with little experimental evidence for intermediates, although an organometallic Co­(III) species is generally implicated. Herein, we describe a rare example of the preparation and characterization of benchtop-stable organometallic aryl-Co­(III) compounds (NMR, HRMS, XAS, and XRD) prepared through a C­(sp²)–H activation, using a model macrocyclic arene substrate. Furthermore, we provide crystallographic evidence of an organometallic aryl-Co­(III) intermediate proposed in 8-aminoquinoline-directed Co-catalyzed C–H activation processes. Subsequent insights obtained from the application of our new organometallic aryl-Co­(III) compounds in alkyne annulation reactions are also disclosed. Evidence obtained from the resulting regioselectivity of the annulation reactions and DFT studies indicates that a mechanism involving an organometallic aryl-Co­(III)-alkynyl intermediate species is preferred for terminal alkynes, in contrast to the generally accepted migratory insertion pathway