Ultrafast dynamics of photochromic compound based on oxazine ring opening

Abstract

We have performed a femtosecond pump-probe and nanosecond flash-photolysis measurements on a new type of photochromic molecules. These photochromes incorporate an indolo[2,1-b][1,3]benzoxazine ring system which opens upon UV light excitation and closes back within a few tens of ns. The details of ring opening and spectral properties of the photoproducts have been studied by investigating the spectral signatures of the model compounds representing separate structural parts of the photochromic switch. Comparison of the photoinduced dynamics of the model compounds and those of photochromic molecule has revealed a detailed molecular picture of the light-driven switch function.

Light-Induced Ring-Closing Dynamics of a Hydrogen-Bonded Adduct of Benzo[1,3]oxazine in Protic Solvents

“…The absorption at ∼555 nm is ascribed to the S 0 → S 1 transition of p-IN, but the origin of the small peak at around 400 nm appearing together with the solvatochromism of benzo­[1,3]­oxazine was not clear before. The reported absorption maxima of indoline, 4-nitrophenol, and 4-nitrophenolate chromophores in MeCN are ∼290, ∼309, and ∼415 nm, respectively, clearly resembling the spectral bands in Figure A . Because of these similarities, for comparative purposes benzo­[1,3]­oxazine was dissolved in excess Bu 4 NOH–MeCN and HCl–MeCN solutions (Scheme ; further detailed absorption spectra are shown in section S2 in the Supporting Information) to get the 4-nitrophenolate and 4-nitrophenol chromophores, respectively. , The wavelengths of these absorption peaks are listed in Table .…”

“…Another band with a maximum at 416 nm qualitatively coincides with the reported absorption of 4-nitrophenolate at 415 nm. 22,36 On the other hand, in HCl−MeCN the absorption spectrum of the completely protonated IN is dominated by two distinct bands at 306 and 562 nm and lacks the ∼400 nm absorption seen for p-IN. On the basis of the above comparative analysis, it was 1B).…”

Synthesis, crystal structures, and laser flash photolysis of 3-nitro-7a,15-methanonaphtho[1',2':6,7][1,3]oxazepino[3,2-a]indole derivatives

“…Flash photolysis experiments were performed using a nanosecond Q-switched Nd:YAG laser (EKSPLA NL301), and pulses of the third harmonic (wavelength -355 nm, duration -6 ns) were applied for excitation. 19 The energy of the pulses for flash photolysis was approximately 3.5 mJ. Sample transmission was probed using light flashes with a duration of ~100 μs generated by a laser-synchronised Xe lamp covering the spectral range of 380-850 nm.…”

“…These photogenerated short-lived species are thermally unstable and revert to the ground state on a nanosecond time scale. [18][19][20][21] Molecules of 5-nitronaphtho[2′,1′:5,6]- [1,3]oxazino [2,3-k]carbazole 1 under UV-laser excitation undergo a similar ring-opening to afford the unstable zwitterionic compound 2, possessing the 4-nitro-1-naphtholate chromophore, and revert to the closed form in a few nanoseconds (Scheme 1). 22 Derivatives of nitroindolo [2,1-b] [1,3]benzoxazines have found application in the development of photoswitchable fluorescent probes, 23 luminescent quantum dots 24 and chemosensors.…”

Electrocyclizations of Conjugated Azapolyenes Produced in Reactions of Azaheterocycles with Metal Carbenes

“…The most common type of electrocyclic reactions of azapolyenes is 1,6-electrocyclization, the products of which are aza and oxaza analogs of cyclohexa-1,3-diene. There are a limited number of reliable methods for the preparation of oxaza analogs of cyclohexa-1,3-diene that makes the 1,6-electrocyclization of azapolyenes a promising synthetic alternative [34][35][36].…”