Biphotochromic System Research Articles

Stepwise photochromism of bisnaphthopyrans exhibiting an excitation intensity-dependent color change.

Non-linear photoresponses against excitation light intensity are important for the development of attractive photofunctional materials exhibiting high spatial selective photoswitching that is not affected by weak background light. Biphotochromic systems composed of two fast photochromic units have the potential to show a stepwise two-photon absorption process in which the optical properties can be non-linearly controlled by changing the excitation light conditions. Herein, we designed and synthesized novel bisnaphthopyran derivatives containing fast photoswitchable naphthopyran units. The bisnaphthopyran derivatives show a stepwise two-photon-induced photochromic reaction upon UV light irradiation accompanied by a drastic color change due to a large change in the molecular structure between the one-photon product and the two-photon product. Consequently, the color of the bisnaphthopyran derivatives can be non-linearly controlled by changing the excitation intensity. This characteristic photochromic property of the biphotochromic system provides important insight into advanced photoresponsive materials.

Spirooxazine-Fulgide Biphotochromic Molecular Switches with Nonlinear Optical Responses across Four States

A new type of prototypical biphotochromic switches combining spirooxazine and fulgide has been synthesized, and their nonlinear optical (NLO) responses have been theoretically studied on the basis of density functional theory (DFT). Our DFT calculations show that the introduction of a fulgide fragment (E and C) into the spirooxazine host can largely enhance the static second- and third-order NLO responses. Moreover, the photoisomerization of spirooxazine derivatives (SO-E and SO-C) brings forth a pronounced change in the geometry accompanied by the formation of a larger π-conjugated system, and thus the corresponding merocyanine derivatives (PMC-E and PMC-C) obtain ∼3.5-times enhancement of static second- and third-order NLO responses. Nevertheless, the difference in NLO responses between the E-form series (SO-E and PMC-E) and the C-form series (SO-C and PMC-C), respectively, is not substantial, which means the fulgide fragment in the prototypical biphotochromic system does not considerably differentiate ...

Synthesis and photochromic behavior of mono-, and biphotochromic system linked by p-phenylene bridge

The synthesis of mono- and bis-1,3-diazabicyclo[3.1.0]hex-3-ene derivatives with indole ring and p-phenylene spacer, which behave as photochromic materials, is reported. The structure–photochromic behavior relationship (SPBR) of the synthesized compounds has been analyzed.

Controlled Conversion of Isomers in a Hybrid Biphotochromic System

[reaction: see text] The photochromic performance of a hybrid system connecting naphthopyran and dithienylethene was investigated, and the photochemistry of eight different isomers was explored by choosing an appropriate wavelength of light.

Multiple Addressing in a Hybrid Biphotochromic System

Affairs of state: Investigation of the photochromic properties of a combined naphthopyran and diarylethene biphotochromic system (1) has revealed that four different states with entirely different absorption behaviors are formed. Opening of the naphthopyran ring leads to conjugation and electronic connection of both photochromes, while closure of the open diarylethene system extends the π-electron system over the whole molecule.

Multiple Addressing in a Hybrid Biphotochromic System

Vier ungleiche Brüder: Ein aus einer Naphthopyran- und einer Diaryletheneinheit bestehendes biphotochromes System (1) bildet vier Zustände mit ganz unterschiedlichem Absorptionsverhalten. Das Öffnen des Naphthopyranrings hat Konjugation und elektronische Verknüpfung der beiden Photochrome zur Folge, das Schließen des offenen Diarylethensystems dehnt das π-Elektronensystem über das ganze Molekül aus.

ChemInform Abstract: Synthesis and Unexpected Photochemical Behavior of Biphotochromic Systems Involving Spirooxazines and Naphthopyrans Linked by an Ethylenic Bridge.

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Synthesis and unexpected photochemical behaviour of biphotochromic systems involving spirooxazines and naphthopyrans linked by an ethylenic bridge

Using the Wittig reaction, six new biphotochromic compounds have been prepared by the coupling of conveniently functionalised spiro[indoline–naphthoxazines] and naphthopyrans. Compared to molecules taken individually, unusual photochromic behaviour has been detected with compounds for which a double bond of Z-configuration links both entities by the 5 or 5′ positions of the naphthalenic parts. Indeed, in this case the thermally stable uncoloured and coloured forms (bistable system) can be photochemically converted acting as photochemical switches.

Photobehaviour of Z‐1,2‐di‐(3′‐methoxynaphth‐2′‐yl)ethene as model compound of biphotochromic supermolecules with Z‐ethenic bridge

This work is part of a research project aimed at investigating the behaviour of biphotochromic supermolecules where two photochromic units of the spirooxazine or chromene series are linked through a conjugated or unconjugated spacer. Preliminary investigations showed that the compounds with ethane, acetylene or ester bridges behave as classical photochromes while those with an ethene bridge showed good coloration accompanied by unusual thermal irreversibility at room temperature. The temperature effect on the spectral behaviour allowed such irreversibility to be explained by the occurrence of a cyclization process at the central ethene bond, typical of Z‐diarylethenes. To better understand this photobehaviour, a deep investigation of a model molecule, Z‐1,2‐di‐(3′‐methoxynaphth‐2′‐yl)ethene, was carried out. This paper reports the results obtained on the model molecule and two biphotochromic systems containing benzochromene and spirooxazine units.

Biphotochromic Norbornadiene Systems

Novel biphotochromic systems containing two norbornadiene moieties in one molecule or one norbornadienyl group in 2-N-(3-phenylnorbornadiene-2-carbonyl)]-N-arylaminomethylene-(2H) benzo[b]thiophenones have been prepared. Under UV/VIS irradiation the latter compounds undergo Z/E-isomerktion acompanied by N → O acyl rearrangement and valence isomerization in the norbornadiene fragment. Bis-norbornadienyl derivatives upon irradiation convert through stepwise isomerization into corresponding quadricyclanes. The back reactions are catalyzed with trifluoroacetic acid at room temperature.

Novel bi-photochromic systems: dihydroindolizines with a Schiff base moiety

In this paper, we describe the properties of novel bi-photochromic compounds resulting from a combination of the recently reported photochromic [1,8a]-dihydroindolizines with Schiff bases in the crystalline state, in rigid glasses and in solution.