Molecular logic circuit based on a multi-state mononuclear platinum(ii) terpyridyl complex

Abstract

A new type of multi-state platinum(II) terpyridyl acetylide complex: platinum(II) 4′-(4-dimethylaminophenyl)-2,2′ : 6′,2′′-terpyridyl ferrocenyl acetylide (1), together with its reference complexes: platinum(II) 4′-(4-methylphenyl)-2,2′ : 6′,2′′-terpyridyl ferrocenyl acetylide (2), platinum(II) 4′-(4-dimethylaminophenyl)-2,2′ : 6′,2′′-terpyridyl phenyl acetylide (3) and platinum(II) 4′-(4-methylphenyl)-2,2′ : 6′,2′′-terpyridyl phenyl acetylide (4), are designed and synthesized. UV–vis–NIR absorption and electrochemical studies demonstrate that complex 1 possesses three ordered intraligand charge transfer (ILCT), ligand-to-ligand charge transfer (LLCT) and metal-to-ligand charge transfer (MLCT) states, and the successive modulation of the intramolecular ILCT, LLCT and MLCT states in a single mononuclear platinum(II) complex 1 is well evidenced by their reference complexes 2–4. More interestingly, a near-infrared absorption band ranging from 720–1000 nm was clearly observed for complexes 1 and 2 upon oxidation of the σ-bonded ferrocene–ethynyl group by Fe(ClO₄)₃, which was tentatively assigned to platinum(II)-disturbed ligand-to-metal charge transfer (LM′CT) of the ferrocenium group. These promising features allow us to integrate the multiple states to reproduce basic logic operations at the molecular level. A four-state (LLCT, ILCT, MLCT and LM′CT) molecular switch of complex 1 that responds to the stimulation of H⁺, Fe(ClO₄)₃ and Zn producing four outputs has been encoded in binary digits. The logic function executed by complex 1 is equivalent to that of a combinational logic circuit integrating seven or eight logic functions as AND, OR, NOT. A three-input-four-output molecular logic circuit has been established.