Photochromic Oxazines with Extended Conjugation

Abstract

We synthesized four compounds with indole and benzooxazine fragments fused in their molecular skeleton and differing in the substituent in the para position, relative to the oxygen atom, of their phenoxy chromophore. This particular substituent extends the conjugation of the phenoxy chromophore and shifts its absorption bathochromically by up to 60 nm, relative to a parent compound with a 4-nitrophenoxy group. The 1,3-oxazine ring of all compounds opens upon addition of base to generate a hemiaminal incorporating a phenolate chromophore. Once again, the substituents on this fragment shift its absorption bathochromically by up to 60 nm, relative to the parent compound. Upon laser excitation at a wavelength within the absorption range of the phenoxy chromophore, the 1,3-oxazine ring of the compound incorporating a 4-nitrophenyl substituent opens in less than 6 ns to generate a zwitterionic isomer with a quantum yield of 0.11 in acetonitrile. Under these conditions, the photogenerated isomer has

Redefining the established understanding of excitation dynamics of photochromic oxazines

“…[1][2][3][4][5][6][7][8][9] However, tiny long-lived components were observed in most of the reported cases: instead of decaying to zero, kinetic traces retain a slight offset, extending beyond the timescale of hundreds of nanoseconds. As was shown earlier, in methanol both studied compounds have different dominant relaxation pathways, hence different efficiencies of the formation of the long-lived species.…”

Nucleophilic Addition of Amines to Ruthenium Carbenes: ortho‐(Alkynyloxy)benzylamine Cyclizations towards 1,3‐Benzoxazines

“…Interestingly, the functionalized 4‐, 5‐, and 6‐halo‐substituted benzylamines could be efficiently converted into their corresponding halo‐substituted 1,3‐benzoxazines 2 f – i in fairly good yields. Further manipulation of the above aryl bromides and chlorides using palladium‐catalyzed cross‐coupling reactions provide an easy entry to polysubstituted benzoxazines 19. Notably, cyclization of the naphthylamine derivative 1 j smoothly gave the naphthoxazine 2 j in very good yield.…”

A Synthetic Strategy for the Structural Modification of Photoactivatable BODIPY‐Oxazine Dyads

“…Thus, the introduction of a styryl substituent on the photocleavable component of 4 does not prevent photoactivation in contrast to previous structural modifications, which resulted in the complete suppression of the photochemical transformation. [41][42][43] However, styryl substitution has a depressive effect on the efficiency of the process relative to 1, which has a Ac of 2 × 10 -3 under otherwise identical experimental conditions. [28] ).…”

“…Structural modifications aimed at extending electronic conjugation in these heterocyclic chromophores, however, tend to alter their excitation dynamics and, often, prevent their photochemical transformation altogether. [41][42][43] The identification of synthetic strategies to regulate the absorption properties of these compounds without suppressing their photoresponsive character is a significant challenge. These considerations suggested the possibility of exploring the influence of styryl substitution on the behavior of our molecular switches.…”