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We have prepared the photo‐labile benzoic acid esters and the acid‐labile tert‐butoxycarbonyl esters of Sudan I and Sudan Red B, two representatives of the ortho‐phenylazonaphthol dye family, exhibiting hydroxyazo–hydrazone tautomerism with the hydrazone as the strongly favored form. The chromophores obtained are “locked” in an exclusive azo configuration and exhibit absorbance spectra which are dramatically blue‐shifted (more than 100 nm) and have strongly reduced extinction coefficients when compared to their parent chromophores. Thus, the esters of the orange dye Sudan I exhibit an absorption maximum in the ultraviolet (UV) regime, and the esters of the red dye Sudan Red B appear yellow. Depending on the nature of the ester moiety, by irradiation with UV light or by exposure to preferentially photochemically released acidic species at elevated temperatures, these esters can be reverted to the parent, highly tinctured Sudan I and Sudan Red B, respectively. Unlike conventional chromogenic systems, these dyes are compatible with melt‐processible polymers and do not require any wet‐chemical development. In polymer films comprised of these chromogenic dyes, color patterns can be produced directly by masked irradiation. We here report on the synthesis, spectral properties, and conversion kinetics of these novel chromogenic dyes, which may be potentially suitable for marking and labeling goods in a lithographic process and for optical data storage and sensing applications.
We have prepared the photo‐labile benzoic acid esters and the acid‐labile tert‐butoxycarbonyl esters of Sudan I and Sudan Red B, two representatives of the ortho‐phenylazonaphthol dye family, exhibiting hydroxyazo–hydrazone tautomerism with the hydrazone as the strongly favored form. The chromophores obtained are “locked” in an exclusive azo configuration and exhibit absorbance spectra which are dramatically blue‐shifted (more than 100 nm) and have strongly reduced extinction coefficients when compared to their parent chromophores. Thus, the esters of the orange dye Sudan I exhibit an absorption maximum in the ultraviolet (UV) regime, and the esters of the red dye Sudan Red B appear yellow. Depending on the nature of the ester moiety, by irradiation with UV light or by exposure to preferentially photochemically released acidic species at elevated temperatures, these esters can be reverted to the parent, highly tinctured Sudan I and Sudan Red B, respectively. Unlike conventional chromogenic systems, these dyes are compatible with melt‐processible polymers and do not require any wet‐chemical development. In polymer films comprised of these chromogenic dyes, color patterns can be produced directly by masked irradiation. We here report on the synthesis, spectral properties, and conversion kinetics of these novel chromogenic dyes, which may be potentially suitable for marking and labeling goods in a lithographic process and for optical data storage and sensing applications.
In ewei soeben an dieser Stelle '> erschienenen Arbeiten iiber die Lichtabsorption von ortho-Oxyazokorpern und deren Athern und Estern kommen B u r a w o y und M a r k o w i t s c h zu dem SchluO, daO die freien ,,ortho-Oxyazoverbindungen" i n Wirklichkeit samtlich Ci~inon-~henylhydrazone seien. Nun sol1 eine Formel nicht nur einer, sondern nach Moglichkeit allen Eigenschaften einer Verbindung gerecht werden; es ist daher zu priifen, wie weit die fur jene Substanzen erneut vorgeschlagene Hydrazon-Formel diese Bedingung erfullt.Hinsichtlich des chemisciien Verhaltens 1a8t sich folgendes sagen:1. Die oft an Unloslichkeit grenzende gerinye LiiYlichReit vieler ortho-Oxyazokorper in Laugen, die fruher als Argument fur ihre Hydrazon-Natur angefuhrt wurde, ist bedeutnngslos. Denn auf der einen Seite begegnet man der Erscheinung, da8 Substanzen trotz zweifellos vorhandenen phenolischen Hydroxyls alkaliunloslich sind, verhaltnismal3ig haufig, und zwar bei den verschiedenartigsten Abkommlingen von Phenolen.a) Auf der anderen Seite werden manche ortho-Oxyazoverbindungen ohne Schwierigkeit von wafirigen Laugen aufgenommen. Beispielsweise lost sich der einfachste Korper dieser Art, das o-Oxyazobenzol, wie schon B a m b e r g e r 3 ) fand, in verdunnter Natronlauge ebenso leicht wie ein para-Derivat. 2. Bedeutung hat dagegen die von H. G o l d s c h m i d t und Low-Beer4) festgestellte Tatsache, daO sich Phenyl-I) A. 503, 180; 604, 'il (1933). 8, Vgl. z. B. A u w e r s , B. 34, 4256 (1901); 39, 3160 (1906); Anselmino, B. 36, 4099 (1902); R o g o w , J. pr. [2] 79, 315 (1905). -Vgl. ferner die groBe Klasse der alkaliunliislichen ,,Phenolbromide".
Kuhn und Bar, Konstitution derOxy-azo-verbindungen. 143 -70.703 3# 350 *) B. 17, 3026 (1884). Annalen dex Cher.de. 616. Band. 10
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