Switching or blinking? – The switching behaviour of single photochromic triads

Photochromic molecules can be interconverted between two bistable conformations by light [1–3]. Irie and coworkers described a strategy to achieve superior fluorescence characteristics and outstanding switching characteristics of a photochromic unit by linking strong fluorophores covalently to photochromic building blocks [3,4]. Accordingly, we synthesised molecular triads that consist of two perylene bisimide (PBI) fluorophores covalently linked to a dithienylcyclopentene (DCP) photochromic switch, see fig. 1. Such kinds of triads are promising candidates for super-resolution microscopy like RESOLFT and PALM [5,6], or can be used as optical transistors or memories [4,7].