Acid-Base Sensors Based on Novel Quinone-Type Dyes

We present a detailed study on the acid–base behaviour of a family of “potentially antiaromatic” p‐benzoquinonediimine ligands. These 12π electron molecules can be considered as constituted of two chemically connected but electronically not conjugated 6π‐electron subunits. Upon successive protonation, “mono” and “double” cyanine‐type chromophores are generated in solution and allow a precise and sensitive spectrophotometric detection. These molecules represent a new class of tunable quinones whose electronic and structural properties can be triggered by proton input, as established by a complete physico‐chemical study involving a combination of potentiometric and spectrophotometric methods (absorption and emission). A new class of tunable quinonoids has been developed using a p‐benzoquinonediimine which contains N‐benzyl groups as the light‐emitting components and four nitrogen atoms as protonation sites. The electronic and structural properties can be triggered by proton input (see scheme), as established by a complete physicochemical study involving a combination of potentiometric and spectrophotometric methods (absorption and emission).