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 cucurbituril 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.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- host-guest systems