A Photobasic Functional Group

Abstract

Controlling chemical reactivity using light is a longstanding practice within organic chemistry, yet little has been done to modulate the basicity of compounds. Reported herein is a triazabutadiene that is rendered basic upon photoisomerization. The pH of an aqueous solution containing the water-soluble triazabutadiene can be adjusted with 350 nm light. Upon synthesizing a triazabutadiene that is soluble in aprotic organic solvents, we noted a similar light-induced change in basicity. As a proof of concept we took this photobase and used it to catalyze a condensation reaction.

Light‐Activated Triazabutadienes for the Modification of a Viral Surface

“…Thus, this chemical functionality can be viewed as a protecting group for reactive aryl diazonium ions. We also reported that this functionality undergoes a photo‐induced isomerization that enables the release the aryl diazonium ion at higher pH . It is important to note that this light‐dependent reactivity differs significantly from those of photo‐reactive groups in chemical biology.…”

“…We also reported that this functionality undergoes a photo-induced isomerization that enables release the aryl diazonium ion at higher pH. [9] It is important to note that this light-dependent reactivity differs significantly from other photo-reactive groups in chemical biology. Whereas other functional groups generate reactive carbenes or radical species [10] the photo-isomerized triazabutadiene simply accelerates formation of aryl diazonium ions by similar protonation-dependent mechanisms as the reaction that occurs in the dark.…”

“…[9] We hypothesized then, that photo-isomerization of a previously occluded E isomer conjugated to a protein surface might expose the critical nitrogen atom to the aqueous environment. This isomer would enable protonation and aryl diazonium ion release at a pH that is neutral or even mildly basic.…”

“…Benzene diazonium ions are known to undergo photochemical loss of nitrogen to generate benzene radicals, but we had previously shown that the benzene diazonium ions coming from triazabutadienes could be trapped with resorcinol in the presence of light. [9] The specter of radical chemistry still loomed, so to test this we synthesized a fluorophore conjugated to a simple phenyl substituent ( 7 ). True to our desired reactivity, this fluorophore did not significantly modify the BSA-bound diazonium ion (Figure 3a).…”

Excited-State Hydroxide Ion Release From a Series of Acridinol Photobases

“…More recently, the reversibility was achieved using cistrans photoisomerization as a way to control the basicity of the photoactive molecule. [41][42] Here, we show that the irradiation of acridinol photobase can be utilized to drive a Michael addition reaction. In specific, the reaction between dimethylmalonate and nitrostyrene was triggered using AcrOMe photobase, which releases the methoxide ion upon excitation.…”