CCVII.—Studies in phototropy and thermotropy. Part III. Arylideneamines

Senier, Alfred; Shepheard, Frederick George; Clarke, Rosalind

doi:10.1039/ct9120101950

Cited by 48 publications

(28 citation statements)

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“…In the final refinement, the chemical restraints were applied to the trans-keto form. The occupancy factor of the trans-keto form became 0.117 (2). Then the crystal was irradiated with a xenon lamp (SAN-EI SUPER BRIGHT 152S with USHIO xenon short-arc lamp UXL-151DO) at 265 K. The crystal color changed from red to colorless.…”

Section: Methodsmentioning

confidence: 99%

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Elongated Lifetime of Unstable Colored Species by Intermolecular Hydrogen Bond Formation in Photochromic Crystals

Johmoto

Sekine

Uekusa

et al. 2009

Bulletin of the Chemical Society of Japan

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The crystallization of N-3,5-di-tert-butylsalicylidene-3-carboxyaniline (1) from a methanol solution gave three crystal forms, 1¡, 1¢, and 1£. The colorless 1¡ and pale yellow 1¢ turned red when they were irradiated with UV light whereas orange 1£ showed no color change. The lifetimes of the colored crystals were estimated to be 17 and 780 min at room temperature for 1¡ and 1¢, respectively, from IR spectra. The structure of the colored 1¡ crystal was analyzed by X-ray at 93 K. In addition to the original enol form of 1, the trans-keto form appeared on the difference electron density map with an occupancy factor of 0.117(2). This indicates that the color change was caused by the structural change from the enol to trans-keto form, which is the same as the color change previously reported in the crystal of N-3,5-di-tertbutylsalicylidene-3-nitroaniline (2) (lifetime, 1200 min). It was made clear from the structures of the trans-keto forms in the crystals of 1¡, 1¢, and 2 that the lifetime of the unstable colored form should be determined by the possibility and the strength of the intermolecular hydrogen bond formation of the NÍH group of the trans-keto form to the neighboring molecules.Light-induced reversible color change of substances is known as photochromism and organic photochromic compounds have attracted much attention over the past decades for their applications in optic data storage, electronic display systems, optical switching devices, ophthalmic glasses, and so on.1 N-Salicylideneanilines, which are the condensation products of salicylaldehydes and anilines, exhibit photochromism both in solution and in the solid state.2 Photochromic salicylideneanilines are usually pale yellow and exist in the enol form in crystals. It was proposed from spectroscopic data that the hydrogen atom of the hydroxy group is translocated to the imine nitrogen atom on irradiation with ultraviolet light. A subsequent geometrical rearrangement in the excited state is assumed to form a red photoproduct. The deep red color can be erased by irradiation with visible light or by thermal fading in the dark. Although many studies have been carried out over three decades, there remains a controversy about the structure of the colored species.3 In a previous paper, we analyzed directly the structure of the photoinduced colored species of N-3,5-di-tert-butylsalicylidene-3-nitroaniline (2) by X-ray using two-photon excitation, which was the first crystallographic determination of structural change showing reversible photochromism in organic crystals. 4 This crystal was selected because the photoproduct has the longest lifetime among a variety of salicylideneaniline crystals. 5 The molecular structure before irradiation takes the enol form. The pale yellow crystal turned dark red when it was irradiated with laser light of 730 nm, twice the wavelength of the absorption maximum at 365 nm at room temperature. After the laser irradiation, the crystal structure was determined by X-ray diffraction analysis. The difference electron density map sho...

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Section: Methodsmentioning

confidence: 99%

“…2 Photochromic salicylideneanilines are usually pale yellow and exist in the enol form in crystals. It was proposed from spectroscopic data that the hydrogen atom of the hydroxy group is translocated to the imine nitrogen atom on irradiation with ultraviolet light.…”

mentioning

confidence: 99%

Elongated Lifetime of Unstable Colored Species by Intermolecular Hydrogen Bond Formation in Photochromic Crystals

Johmoto

Sekine

Uekusa

et al. 2009

Bulletin of the Chemical Society of Japan

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“…SAs have been classified according to their photochromic or thermochromic properties [1][2][3][4] and are of particular interest to chemists and physicists, owing to their reversible photoreactivity in the solid state. Indeed, success in obtaining and, more importantly, controlling such tailor-made ground and excited-state properties can lead to future applications in such fields as nonlinear optics, organic superconductors, optical sensors, control and measurement of radiation intensity, optical computers, and display systems.…”

Section: Introductionmentioning

confidence: 99%

Polymorphism inN-Salicylideneaniline Reconsidered

Arod

Pattison

Schenk

et al. 2007

Crystal Growth & Design

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ABSTRACT:The aromatic Schiff base N-salicylideneaniline (SA) represents the aristotype of a whole family of chromic derivatives. SA forms two photochromic polymorphs, R 1 and R 2 , both of which feature non-coplanar phenyl rings. Since many details of its reversible photoreactivity are still unexplained, we report the structure of a planar, thermochromic polymorph, named , and propose a new model for the structure of the R 1 -polymorph. Finally, we discuss structure-property relations between the polymorphs and the to R 1 phase transition.

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“…16 only observed phototropy with excitation radiation in the violet and ultraviolet wavelengths. 16 only observed phototropy with excitation radiation in the violet and ultraviolet wavelengths.…”

Section: Salicy Lidene-a N I L I N E (S a )mentioning

confidence: 99%

Phototropic properties of salicylidene-m-toluidine and salicylidene-aniline

Burr¹,

Llewellyn²,

Lothian³

1964

Trans. Faraday Soc.

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On exposure to violet and ultra-violet radiation, crystals of salicyIidene-m-toluidine and of salicylidene-aniline both develop an absorption band with Amax = 4750A. A theory is developed which permits determination of the quantum efficiencies of this reaction (8 and 0.04-049 respectively). This band bleaches in darkness; the rates of bleaching are determined at various temperatures, and activation energies for the bleaching reaction are calculated : 1.28 eV and 0.99-1.65 eV respectively ; the behaviour of S.A. is not simple and the observations are attributed to the occurrence of two crystalline forms having different rates of colouring and bleaching.The bleaching of each compound is accelerated by irradiation within the induced band, and quantum efficiencies of this optical bleaching are determined for A = 5461 A as 0.04 and 0.2 respectively. Oscillator strengths for the induced absorption band are determined (-10-3). It is suggested that the colouring process is due to the intramolecular transfer of an H atom during the bending vibration of the C-CH=N group in the electroaically excited molecule. The crystal angles of salicylidene-m-toluidine are reported.The phenomenon of phototropy, photochromism 1 or photochromotropy,2 whereby compounds exhibit a reversible change of colour on exposure to electromagnetic radiation of suitable frequency, has been studied by many workers. Review papers 3-5 list compounds which exhibit this property. Usually the colour change occurs in the solid state, but under certain conditions in solution.2The phototropic change may be represented by the reaction, h v A'A'. The reverse reaction normally takes place in the absence of radiation and is accelerated by raising the temperature (thermal bleaching). In some cases, however, if the coloured material is irradiated with radiation lying within the induced absorption band, the reverse reaction is accelerated (optical bleaching).Information on the nature of the mechanism may be obtained by measuring the differing physical properties of the material in the states A and A'; e.g., dielectric constant,6 magnetic susceptibility,7 X-ray diffraction 6, 8 and optical absorption spectra.9~ 10 This paper describes the apphation of spectrophotometric techniques to determine the reaction kinetics for two anils-salicylidene-m-toluidine (S.M.T.) and salicylidene-aniline (S.A.). EXPERIMENTALMeasurements were made using a quartz prism monochromator on (i) the absorption spectra in states A and A' with the E vector of the measuring radiation parallel to the principal * now at College of Technology, Letchworth.

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CCVII.—Studies in phototropy and thermotropy. Part III. Arylideneamines

Cited by 48 publications

References 0 publications

Elongated Lifetime of Unstable Colored Species by Intermolecular Hydrogen Bond Formation in Photochromic Crystals

Elongated Lifetime of Unstable Colored Species by Intermolecular Hydrogen Bond Formation in Photochromic Crystals

Polymorphism inN-Salicylideneaniline Reconsidered

Phototropic properties of salicylidene-m-toluidine and salicylidene-aniline

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