Single-Molecule Investigation of Initiation Dynamics of an Organometallic Catalyst

Abstract

The action of molecular catalysts comprises multiple microscopic kinetic steps whose nature is of central importance in determining catalyst activity and selectivity. Single-molecule microscopy enables the direct examination of these steps, including elucidation of molecule-to-molecule variability. Such molecular diversity is particularly important for the behavior of molecular catalysts supported at surfaces. We present the first combined investigation of the initiation dynamics of an operational palladium cross-coupling catalyst at the bulk and single-molecule levels, including under turnover conditions. Base-initiated kinetics reveal highly heterogeneous behavior indicative of diverse catalyst population. Unexpectedly, this distribution becomes more heterogeneous at increasing base concentration. We model this behavior with a two-step saturation mechanism and identify specific microscopic steps where chemical variability must exist in order to yield observed behavior. Critically, we reveal how structural diversity at a surface translates into heterogeneity in catalyst behavior, while demonstrating how single-molecule experiments can contribute to understanding of molecular catalysts.

Anticancer and Antibacterial Activity of Transition Metal Complexes

“…Many metal complexes have been synthesized thereafter that contain disparate transition metals, for example titanium,, zirconium, vanadium, niobium,, tantalum, iridium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, palladium, osmium, rhodium, and platinum . Transition metal complexes have multiple utilization in a wide range of areas such as catalysis, optics,, electroluminescent devices,, agricultural and biocidal use, and mostly in biological fields including anticancer, antibacterial, and antifungal applications. Though organic compounds have pharmaceutical activity, a prime asset of these metal‐fabricated drugs over organic‐fabricated drugs is their mastery to alter coordination number, geometry, and redox states.…”

Catalytic single-chain polymeric nanoparticles at work: from ensemble towards single-particle kinetics

“…[29][30][31][32][33][34][35][36][37][38][39][40][41] Although mostly applied for investigating enzymatic reactions, the fluorogenic substrate reporter systems also allow for studying non-enzymatic processes in real time. [34][35][36][37][38]40,41 Upon cleavage, the initially nonfluorescent substrate is converted into a highly fluorescent product molecule. As every turnover yields one fluorescent product molecule, a detailed and straightforward kinetic analysis is facilitated.…”

Kinetics of the Same Reaction Monitored over Nine Orders of Magnitude in Concentration: When Are Unique Subensemble and Single‐Turnover Reactivity Displayed?

“…[1][2][3] Themain challenge with identifying the behavior of individual molecular catalysts is the ensemble averaging inherent to traditional analytical techniques.M olecular catalysts are typically depicted as proceeding through uniform catalytic cycles because of their well-defined ligand coordination sphere;however, it is poorly understood if they display reactivity that deviates from uniformity,w hat reaction conditions cause these deviations,a nd when and how these deviations could be observed. Employing fluorescence microscopy [4][5][6][7][8][9][10][11] with sensitivity sufficient for the detection of single insertion reactions,w er ecently reported the first imaging of single turnover at individual molecular catalysts. [1,2] These experiments begin to realize the potential of single-molecule techniques to reveal the otherwise obscured nonuniform behavior of molecular catalysts;s pecifically,i t was discovered that individual molecular ruthenium polymerization catalysts proceed through distinct, abruptly changing kinetic states,p lausibly dictated by changing local environments within growing polymer aggregates.…”