Photochromic oxazines with extended conjugation

Michael Åxman Petersen, Erhan Deniz, Mogens Brøndsted Nielsen, Salvatore Sortino, Francisco Raymo

Research output: Contribution to journalArticle

30 Citations (Scopus)

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 a lifetime of 29 ns and reverts spontaneously to the original species with first-order kinetics. Furthermore, this photochromic system tolerates hundreds of switching cycles with no sign of degradation even in the presence of molecular oxygen. However, the excitation dynamics of the other three compounds, incorporating a 4-nitrobiphenyl, 4-nitrostyryl or 4-nitrophenylethynyl substituent, are dominated by intersystem crossing. Consistently, the corresponding transient spectra reveal predominantly triplet-triplet absorptions. Thus, our studies demonstrate that the excitation wavelength and color of this class of photochromic compounds can be regulated by extending the conjugation of their phenoxy fragment with negligible influence on the photochromic performance only if the structural modification does not encourage intersystem crossing.

Original languageEnglish
Pages (from-to)4333-4339
Number of pages7
JournalEuropean Journal of Organic Chemistry
Issue number25
DOIs
StatePublished - Sep 1 2009

Fingerprint

Oxazines
Chromophores
conjugation
chromophores
fragments
Isomers
isomers
excitation
Wavelength
Laser excitation
Molecular oxygen
rings
shift
indoles
Quantum yield
musculoskeletal system
wavelengths
acetonitrile
oxygen atoms
degradation

Keywords

  • Heterocycles
  • Laser chemistry
  • Molecular devices
  • Oxazines
  • Photochromism
  • Photolysis

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Photochromic oxazines with extended conjugation. / Petersen, Michael Åxman; Deniz, Erhan; Nielsen, Mogens Brøndsted; Sortino, Salvatore; Raymo, Francisco.

In: European Journal of Organic Chemistry, No. 25, 01.09.2009, p. 4333-4339.

Research output: Contribution to journalArticle

Petersen, Michael Åxman ; Deniz, Erhan ; Nielsen, Mogens Brøndsted ; Sortino, Salvatore ; Raymo, Francisco. / Photochromic oxazines with extended conjugation. In: European Journal of Organic Chemistry. 2009 ; No. 25. pp. 4333-4339.
@article{cf8fb37fe6ac4ace9ae1b2a8d4eeef55,
title = "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 a lifetime of 29 ns and reverts spontaneously to the original species with first-order kinetics. Furthermore, this photochromic system tolerates hundreds of switching cycles with no sign of degradation even in the presence of molecular oxygen. However, the excitation dynamics of the other three compounds, incorporating a 4-nitrobiphenyl, 4-nitrostyryl or 4-nitrophenylethynyl substituent, are dominated by intersystem crossing. Consistently, the corresponding transient spectra reveal predominantly triplet-triplet absorptions. Thus, our studies demonstrate that the excitation wavelength and color of this class of photochromic compounds can be regulated by extending the conjugation of their phenoxy fragment with negligible influence on the photochromic performance only if the structural modification does not encourage intersystem crossing.",
keywords = "Heterocycles, Laser chemistry, Molecular devices, Oxazines, Photochromism, Photolysis",
author = "Petersen, {Michael {\AA}xman} and Erhan Deniz and Nielsen, {Mogens Br{\o}ndsted} and Salvatore Sortino and Francisco Raymo",
year = "2009",
month = "9",
day = "1",
doi = "10.1002/ejoc.200900604",
language = "English",
pages = "4333--4339",
journal = "Annalen der Pharmacie",
issn = "0075-4617",
publisher = "Wiley-VCH Verlag",
number = "25",

}

TY - JOUR

T1 - Photochromic oxazines with extended conjugation

AU - Petersen, Michael Åxman

AU - Deniz, Erhan

AU - Nielsen, Mogens Brøndsted

AU - Sortino, Salvatore

AU - Raymo, Francisco

PY - 2009/9/1

Y1 - 2009/9/1

N2 - 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 a lifetime of 29 ns and reverts spontaneously to the original species with first-order kinetics. Furthermore, this photochromic system tolerates hundreds of switching cycles with no sign of degradation even in the presence of molecular oxygen. However, the excitation dynamics of the other three compounds, incorporating a 4-nitrobiphenyl, 4-nitrostyryl or 4-nitrophenylethynyl substituent, are dominated by intersystem crossing. Consistently, the corresponding transient spectra reveal predominantly triplet-triplet absorptions. Thus, our studies demonstrate that the excitation wavelength and color of this class of photochromic compounds can be regulated by extending the conjugation of their phenoxy fragment with negligible influence on the photochromic performance only if the structural modification does not encourage intersystem crossing.

AB - 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 a lifetime of 29 ns and reverts spontaneously to the original species with first-order kinetics. Furthermore, this photochromic system tolerates hundreds of switching cycles with no sign of degradation even in the presence of molecular oxygen. However, the excitation dynamics of the other three compounds, incorporating a 4-nitrobiphenyl, 4-nitrostyryl or 4-nitrophenylethynyl substituent, are dominated by intersystem crossing. Consistently, the corresponding transient spectra reveal predominantly triplet-triplet absorptions. Thus, our studies demonstrate that the excitation wavelength and color of this class of photochromic compounds can be regulated by extending the conjugation of their phenoxy fragment with negligible influence on the photochromic performance only if the structural modification does not encourage intersystem crossing.

KW - Heterocycles

KW - Laser chemistry

KW - Molecular devices

KW - Oxazines

KW - Photochromism

KW - Photolysis

UR - http://www.scopus.com/inward/record.url?scp=68949128664&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=68949128664&partnerID=8YFLogxK

U2 - 10.1002/ejoc.200900604

DO - 10.1002/ejoc.200900604

M3 - Article

AN - SCOPUS:68949128664

SP - 4333

EP - 4339

JO - Annalen der Pharmacie

JF - Annalen der Pharmacie

SN - 0075-4617

IS - 25

ER -