The Photoinduced Electrocyclization Reaction of Triphenylamine (TPA) in Sustainable and Confined Micellar Solutions: A Steady‐State and Laser Flash Photolysis Approach

Abstract

The irradiation of triphenylamine (TPA) under homogeneous (cyclohexane, acetonitrile and methanol) and micellar [sodium dodecyl sulfate (SDS), cetyltrimethylammonium chloride (CTAC) and polyethylene glycol monododecyl ether (Brij‐P35)] conditions has been investigated through a combined steady‐state and time‐resolved spectroscopic approach. Photolysis of TPA at 254 nm in different media afforded N‐phenylcarbazole (N−PhCA) as the main photoproduct, and when the photoreaction of TPA was carried out in micellar solution the relative rate of formation of N−PhCA was found to be faster than in homogeneous media due to the environmental confined and hydrophobic micellar core. On the other hand, the transient N‐phenyl‐4a,4b‐dihydrocarbazole (DHC0) was detected and fully characterized via laser flash photolysis. Finally, the location of TPA within the hydrophobic core of the micelle was investigated by 1D and 2D NMR spectroscopic analyses.

Product selectivity in the photoreaction of aryl sulfonates and mesylate of estrone derivatives in sustainable and micellar media: a steady-state investigation

“…In fact, the determination of the extent of localization of guest molecules within the micelle or the co-aggregation between two different kinds of surfactants in water have been often achieved using NOESY experiments. 21,24 Further, satisfactory results using this spectroscopic experiment come from the cross-peaks between the diagnostic signals of the substrates and the surfactants, respectively, which are observed in the contour plots. 21…”

“…21,24 Further, satisfactory results using this spectroscopic experiment come from the cross-peaks between the diagnostic signals of the substrates and the surfactants, respectively, which are observed in the contour plots. 21…”

“…The first approach was then to determine the binding constant ( K b ) between the selected ionic and neutral surfactants (SDS, CTAC, and Brij-P35) and the sulfonic esters 1–5 using UV-visible absorption spectroscopy, which was previously applied with success. 16 c ,21 Briefly, the addition of increasing amounts of surfactant into the sulfonic ester 1–5 solution prepared with water accounts for the bathochromic and hyperchromic shifts of the lower energy absorption band of the steroid, reflecting the extent of binding of such sulfonic esters to the surfactants (for UV-visible chromic shifts, see Fig. S1–S5 in ESI†).…”

“…Some interesting examples regarding the control of the selectivity and yield of the photoproducts within the micelle have been reported in the literature 20 as well as by our research group. 16 c ,21…”

Photoinduced [6π]-Electrocyclic Reaction of Mono-, Di-, and Trisubstituted Triphenylamines in Acetonitrile. A Steady-State Investigation

“…Recently, our research group has also made some interesting contributions to the photoinduced [6π]-electrocyclization reaction of triphenylamine. Thus, the photoreaction was studied under steady-state and time-resolved spectroscopy in different polar and nonpolar solvents as well as in micellar media . Furthermore, co-oxidation of nucleophilic substrates (aryl and alkyl thioethers and triarylphosphines) has been carried out using triphenylamine, tris -(4-bromophenyl)­amine and tris -(2,4-dibromophenyl)­amine as oxidizing photosensitizers in the presence of molecular oxygen, showcasing the usefulness and the versatility of the [6π]-electrocyclization photoreaction. , All these photochemical reactions were performed under mild conditions and at room temperature requiring only molecular oxygen as the oxidizing reagent and providing the corresponding carbazoles in good yields (see Chart ).…”