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

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(ClO(4))(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(ClO(4))(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.