Photoinduced diels-Alder cycloaddition in supramolecular conditions

Diels-Alder photocycloaddition of 9-phenylethynylanthracene results in multiple (4 + 2) and (4 + 4) cycloaddition products in solution, which can be controlled to form specific products under a restricted environment. However, this well-known textbook reaction, has not been explored in materials chemistry. We have exploited the gel phase of a 9- phenylethynylanthracence derivative as a confined medium to specifically yield the (4 + 2) cycloadduct in >90% yield. The photocycloadduct (anti-form) exhibited a blue emission with CIE chromaticity of x = 0.16/y = 0.16. Construction of an organic light emitting device with the photocycloadduct, using a carbazole-based hole trans- porting host, resulted in white light emission with a CIE chromaticity of x = 0.33/y = 0.32. In another report, we describe how this classical photochemistry can be used to modulate the lower critical solution temperature (LCST) of a molecular π-system, which can further be exploited for the controlled trans- mission of solar radiation for the management of indoor heat and light. An amphiphilic anthracene derivative 9- PA-1 exhibited LCST behavior at 27-32°C with a reversible transition from a transparent to an opaque phase in water (1-5mM). Irradiation of a toluene solution of 9-PA-1 with 365 nm light resulted in a (4 + 2) photocycloadduct 9-PA-2, which exhibited a modulated LCST behavior at 25-27°C, at a concentration as low as 6 μM. The photocycloaddition of 9-PA-1 was significantly retarded in water, making it a stable candidate for the design of sustainable smart windows