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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 34, Number 6
BKCSDE 34(6)
June 20, 2013 

Symmetric Bis-Azospiropyrans: Synthesis, Characterization and Colorimetric Study
Farahnaz Nourmohammadian*, Ali Ashtiani Abdi
Bis-azo, Spiropyran, Photoresponsivity, Fluorescence, Photochemically bifunctional
Synthesis and characterization of some novel symmetric bis-azospiropyrans are reported in this study. These bis-azospiropyrans are bifunctional chromophores with two spiropyrans linked by a bis-azo extended aromatic system that produce more color strength (large molar absorption coefficient in mero forms) due to appending two azospiropyran chromophores on one molecule. Comparing to the molar absorption coefficients of the conventional spiropyran chromophores (ε = 0.31 × 104 M−1·cm−1) and mono-azospiropyran chromophores (1.35 × 104 M−1·cm−1), the novel synthesized photochromes showed astonishingly increased molar absorption coefficients (2.3-3.8 × 104 M−1·cm−1) at the same conditions. Such high molar absorption coefficients confers high sensitivity to light and more color intensity of mero form, that leads to improvement of their light sensitivity and better discrimination of spiro (OFF) form from mero (ON) ones in molecular switches. The structures were deduced from their MS, FT-IR, and 1H-NMR spectroscopic data and CHN analysis. All the synthesized photochemically bifunctional compounds revealed fluorescent emission in their colorless form which was faded out after exposing to UV light. Fluorescence quantum yield values of the mero forms were 0.25-0.81 and two high fluorescence quantum yield values (0.60 and 0.81) were found in these series.
1727 - 1734
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