Achievement of information storage at molecular level remains a pressing task in miniaturization of computing technology. One of the promising approaches for its practical realization is development of nanoscale molecular switching materials including redox-active systems. The present work demonstrates a concept of expansion of a number of available redox-states of self-assembled monolayers through supramolecular approach. For this, the authors synthesized an octopus-like heteroleptic terbium(III) bisphthalocyaninate bearing one ligand with eight thioacetate-terminated "tentacles" (octopus-Pc) and a ligand with four crown-ether moieties (H2 [(15C5)4 Pc]). It is shown that octopus-Pc forms stable monolayers on gold, where its face-on orientation allows for subsequent binding of crown-phthalocyanine molecules via potassium ion bridges. This chemistry is utilized to form a heterogeneous bilayer, in which a single molecule thick adlayer brings an additional redox-state to the system, thus expanding the multistability of the system as a whole. All four redox states available to this system exhibit characteristic absorbance in visible range, allowing for the switching to be easily read out using optical density measurements. The proposed approach can be used in wide range of switchable materials-single-molecule magnets, conductive, and optical devices, etc.
Keywords: crown-ethers; molecular switching; phthalocyanine; redox-active monolayers; self-assembled monolayers; supramolecular chemistry.
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