Synthesis and electronic properties of 1,2-hemisquarimines and their encapsulation in a cucurbit[7]uril host

Christian C. Defilippo, Hao Tang, Luca Ravotto, Giacomo Bergamini, Patrizio Salice, Miriam Mba, Paola Ceroni, Elena Galoppini, Michele Maggini

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Abstract

The synthesis of a new class of robust squaraine dyes, colloquially named 1,2-hemisquarimines (1,2-HSQiMs), through the microwave-assisted condensation of aniline derivatives with the 1,2-squaraine core is reported. In CH 3CN, 1,2-HSQiMs show a broad absorption band with a high extinction coefficient and a maximum at around λ=530nm, as well as an emission band centered at about λ=574nm, that are pH dependent. Protonation of the imine nitrogen causes a redshift of both absorption and emission maxima, with a concomitant increase in the lifetime of the emitting excited state. Encapsulation of the chromophore into a cucurbit[7]uril host revealed fluorescence enhancement and increased photostability in water. The redox characteristics of 1,2-HSQiMs indicate that charge injection into TiO 2 is possible; this opens up promising perspectives for their use as photosensitizers for solar energy conversion. Be square! 1,2-Hemiquarimines (see figure), with one unsubstituted or derivatized phenylimine group, can be synthesized from the corresponding 1,2-squaraine. The interesting photophysical and redox characteristics of these dyes make them useful candidates for charge transfer and sensitization studies.

Original languageEnglish (US)
Pages (from-to)6412-6420
Number of pages9
JournalChemistry - A European Journal
Volume20
Issue number21
DOIs
Publication statusPublished - May 19 2014

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All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry

Keywords

  • cucurbiturils
  • dyes/pigments
  • host-guest systems
  • photochemistry
  • sensitizers
  • squaraines

Cite this

Defilippo, C. C., Tang, H., Ravotto, L., Bergamini, G., Salice, P., Mba, M., ... Maggini, M. (2014). Synthesis and electronic properties of 1,2-hemisquarimines and their encapsulation in a cucurbit[7]uril host. Chemistry - A European Journal, 20(21), 6412-6420. https://doi.org/10.1002/chem.201400039