Emission properties of a highly fluorescent pyrene dye in solution and in the liquid state

Three novel pyrene dyes substituted by four oligo-ether side chains of varying size have been synthesized. Surprisingly, two of these fluorescent derivatives are liquid at room temperature. The photophysical study of one of these dyes, which is miscible in common organic solvents such as hexane, chloroform and toluene, but also in water, has been performed. It has been shown that this pyrene derivative exhibits a high quantum yield of fluorescence, Φf ∼ 1, and has a high extinction coefficient, i.e. ɛ = 100,000 mol−1 cm−1 l, in diluted n-hexane solution. In water, aggregation takes place and the fluorescence quantum yield decreases considerably. Moreover, the spectroscopic properties of the aggregates formed in water are very close to those of the neat liquid. Therefore, the basic structure of the aggregates formed in water and in the pure liquid are expected to be similar.