New molecular systems for functional dye-based molecular switching of luminescence

Three types of molecular switching processes involving luminescence are reported. The first section deals with photochemical induced switching. The bisarylene-substituted dihydroazulene/vinylheptafulvene (DHA-PA/VHF-PA) couple containing a photoswitchable substructure (photochemical forward and thermal reverse reaction) shows on/off switching of luminescence arising from the fluorescent DHA-PA and the non-fluorescent VHF-PA. The second part pertains to electrochemically induced switching. Benzodifurane quinone BFQ-A can reversibly be reduced to the hydroquinone dianion BFQ-A(2-) in a two-step process via quinone radical anion BFQ-A(.-) BFQ-A and BFQ-A(.-) are non-fluorescent or weakly fluorescent respectively, whereas reduction to BFQ-A(2-) leads to a significant fluorescence. In the third part the generation of electrochemiluminescence (ECL) by the stilbene-like compounds SN-A ON-A and OS-A is described. Electrochemical and optical properties were investigated by cyclic voltammetry and spectroelectrochemical methods.