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Quantitative investigations of thermal and photoinduced J- and H-aggregation of hydrophobic spirooxazines in binary solvent through UV/vis spectroscopy

RSC Advances, ISSN: 2046-2069, Vol: 4, Issue: 40, Page: 20974-20983
2014
  • 11
    Citations
  • 0
    Usage
  • 21
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    11
    • Citation Indexes
      11
  • Captures
    21

Article Description

The aggregation of two hydrophobic spirooxazine dyes has been investigated in water-acetonitrile binary solvent and in presence of sodium dodecylsulfate (SDS). For the thermochromic molecule 1, aggregation is spontaneous and occurs when a large amount of water is added to an acetonitrile solution of the dye. There exists an optimum value of the water-acetonitrile molar ratio giving rise to a sharper H-aggregate visible absorption spectrum. Kinetic analysis of the H-aggregate formation has shown that there is an increase in the sticking probability of the monomers, as the aggregates grow. A subtle interplay between H- and J- aggregation was witnessed by adding small amounts of SDS. This change is so sensitive that this system could be the basis of a new chemosensory technique for SDS assessment. Excess of surfactant induces the collapse of the aggregates and the re-dissolution of the dye under the form of a merocyanine-SDS ion-pair. For the spirooxazine 2, aggregation must be photo-induced. Comparison of the spectral evolutions of the two dyes in the presence of SDS has shown that the opening of the closed spirooxazines paves the way to the merocyanine-SDS ion-pair formation. Reversibility of the aggregation has been suggested to occur when the aggregate size is still small. Finally, reversibility has been checked experimentally by precipitate re-dissolution and spirooxazine recovery. Possible structures and reactivity of the H- and J-aggregates have been deduced. This journal is © the Partner Organisations 2014.

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