Dihydroazulene/Vinylheptafulvene (DHA/VHF) and Molecular Electronics

This chapter focuses on the dihydroazulene/vinylheptafulvene (DHA/VHF) photo-/thermo-switch in the context of molecular electronics. It covers the general properties of this couple as well as synthetic protocols for synthesizing and functionalizing DHA. Functionalization methods rely in particular on the ready incorporation of a bromo substituent at the seven-membered ring of DHA and an iodophenyl at the five-membered ring, allowing for Pd-catalyzed cross-coupling reactions. Synthetically, the emphasis is on how to introduce sulfur end-groups for anchoring DHA molecules to metal electrodes. Single-molecule conductance studies reveal light-controlled conductance switching for several of these junctions. Of additional relevance for molecular electronics, various multimode switches for optical data storage are described.