Photochromic properties of 4′-amino-substituted 2-hydroxychalcones

✍ Scribed by Ryoka Matsushima; Hirotaka Mizuno; Hideki Itoh

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 492 KB
• Volume: 89
• Category: Article
• ISSN: 1010-6030
• DOI: 10.1016/1010-6030(95)04056-l

✦ Synopsis

%bstract 2-Hydroxychalcones with 4'-amino substituents undergo facile photochemical conversion into highly coloured flavylium ions on irradiation ,vith 365--436 nm light in aqueous ethanol solution in the pH region 4-6. The coloured solutions are substantially stable against prolonged rradiation with visible light. The absorption coefficients of the flavylium ions around 530-560 nm are strong (approximately 5 X 104 moltm 3 cm-' ) and well separated from those of the chalcones around 400 nm. Some of the derivatives feature good reversibility for repeated :~hotochemical colouration and thermal reversion without significant fatigue in dilute solution, while others feature high thermal stability. ;;imilar photochemical colouration occurs in many solid polymers, but irreversible thermal bleaching takes place. The photochromic properties ire discussed in terms of the frontier orbital theory.