Subject(s)
Pharmacy Service, Hospital , Pharmacy , Humans , United States , Pharmacists , Surveys and QuestionnairesABSTRACT
Azobenzenes appended with a redox-active arylamino group (redox auxiliary, RA) are prepared and shown to undergo fast, complete, and catalytic ZâE azo isomerization upon electron loss from the RA unit of the azobenzene. The RA-azo structures can be reversibly (EâZâE)n cycled by sequential photo- and electrostimulation. Due to the robust nature of the RAâ¢+-azo radical cation chain carrying species, initiation of electron transfer (ET) catalysis occurs at low levels (1.0-0.04 mol %) of catalytic loading and is effective even at Z-RA-azo concentrations of 10-4-10-5 M, yielding TONs (turnover numbers) of 100-2300 under such dilute conditions. The RA-azo ZâE conversion is demonstrated using chemical oxidation (redox switching), electrochemical oxidation (electro switching), and photochemical oxidation (photoredox switching). The ZâE acceleration is shown to be at least 2 × 109-fold for RA-azo 5. DFT calculations on methyl yellow suggest that a N-centered radical cation of the RA group stabilizes the ZâE N-N twist transition state of the RAâ¢+-azo, yielding a large reduction in the barrier for RAâ¢+-azo compared to neutral RA-azo. The RA-azo structure class has nanomechanical features that can be toggled with photo- and electrostimulation, the latter offering a quick switch for complete ZâE conversion.