Photochemically reversible luminescence lifetime switching in metal-organic systems

We use a diarylethene with solution-stable open and closed forms (1,2-bis(2-methylbenzo[b]thiophen-3-yl) hexafluorocyclopentene), BTF6, as a photochromic energy transfer quencher of the metal-to-ligand charge-transfer (MLCT) based luminescence in [Ru(dpp)(3)](2+), dpp = 4,7-diphenyt-1,10-phenanthroline. As only the closed form of BTF6 serves as a quencher for the MLCT luminescence, and the read (390 nm), write (lambda < 360 nm), and erase (lambda > 500 nm) wavelengths are well-separated, this system potentially represents an economic alternative to covalent systems. For the first time, we demonstrate the concept of using luminescence lifetimes to transduce the photochromic binary state of the quencher as opposed to the intensity-based readout schemes that are traditionally employed. The luminescence quenching process is described in terms of Forster-type resonance energy transfer (RET) enhanced by diffusion.