Toggling the Oxygen Affinity between Anthracenes and Naphthalenes.

ABSTRACT

We present the design of an anthracenyl⎯naphthyl (ANT⎯NAPH) dyad and its application as a luminescent 4-stage photo switch. Both segments can individually react with singlet oxygen to switch off an optical response. In their initial form the larger ANT component reacts significantly faster and thus an ANTO2⎯NAPH stage is turned on, observed by optical response of the remaining NAPH. To reduce its reactivity, ANT is substituted with two pyridine rings. This concept is first investigated and quantified on ANT and NAPH as separated molecules. Upon protonation the reaction of ANT becomes significantly slower. For the three possible pyridyl isomers this effect increases along the order metanitrogen in ortho position, the reaction completely toggles from ANT to NAPH. Application of this concept on the dyad allows to turn on the ANT⎯NAPHO2 stage with optical response of the remaining ANT. The sequence of protonation-oxygenation-neutralization is thereby the only possible way to isolate the unfavored form ANT⎯NAPHO2.  In the dyad ANT and NAPH are directly attached and their coupling constitutes a non-oxygenated third stage, where the NAPH luminescence is quenched and ANT luminescence is enhanced. Reaction of both NAPH and ANT to ANTO2⎯NAPHO2 constitutes the fourth dark stage.