Orientational Control of Circularly Polarized Luminescence from Pyrene Clusters by Using a DNA Scaffold

We have investigated the chiroptical activities of pyrene clusters incorporated within a DNA duplex. Three pyrene derivatives were prepared on d-threoninol linkers to allow incorporation within a DNA strand. DNA scaffolds containing dimers, tetramers, and hexamers of the pyrene derivatives were prepared. The homodimers of 1- and of 4-pyrenecarboxylic acid, but not 2-pyrenecarboxylic acid, emitted intense circularly polarized luminescence signals. Although increasing the number of pyrene units weakened the signal, insertion of natural base pairs between two dimers enhanced its intensity. Interestingly, circularly polarized luminescence intensities varied non-monotonically depending on the number of intervening base pairs, thus indicating the importance of orientation between pyrene dimers. The results presented here could lead to the development of bright circularly polarized luminescence materials and probes.