Functionalised organometallic photoswitches containing dihydropyrene units

Functionalising organic molecular photoswitches with metal complexes has been shown to alter and enhance their switching states. These organometallic photoswitches provide a promising basis for novel smart molecular materials and molecular electronic devices. We have detailed the synthesis and characterisation of mono- and bimetallic half-sandwich ruthenium and iron complexes functionalised with alkynyl dihydropyrenes (DHP). Their electronic and photophysical properties were determined by the use of chemical, electrochemical and spectroelectrochemical techniques. The introduction of the metal alkynyl moiety allows access to additional redox and protonation states not accessible by the DHP alone. An additional metal alkynyl moiety inhibits observable photochromic switching. Analysis of the NIR and IR bands in the mixed valence complexes suggests there is a high degree of charge delocalisation across the DHP. Synthesis of half-sandwich Ru and Fe complexes functionalised with alkynyl dihydropyrenes is described. Unlike the parent DHP ligand, several of the metal alkynyl dihydropyrenes showed evidence of photoswitching as a result of a higher barrier to thermal reversion.