Spectroscopic and electrochemical behavior of a supramolecular tetrapyridylporphyrin encompassing four terpyridine(oxalate)chloridoruthenium(II) complexes and its use in nitrite sensors

Abstract

Supramolecular species combining ruthenium(II) polypyridines and tetrapyridylporphyrins (TPyP) have been employed in electrochemical and molecular sensing devices, because of their unique synergistic properties. In this work, a new tetraruthenated porphyrin, 4-TRoxPyP has been synthesised, encompassing four pyridine bridged [Ru(Cl-tpy)(ox)] complexes (Cl-tpy = chloroterpyridine, ox = oxalate ion). Such species exhibit characteristic electronic transitions of porphyrin and ruthenium polypyridine complexes, such as a Soret band at 414 nm, Q bands at 514 nm, 557 nm and 588 nm and a ruthenium-to-terpy charge-transfer band at 643 nm. A typical tetraruthenated porphyrin redox process has been observed at 0.72 V versus NHE, associated with the peripheral Ru3+/2+ complexes. Their thin films have been prepared by drop casting onto a glassy carbon electrode, and successfully employed in nitrite analysis, by monitoring the chronoamperometric response at the Ru3+/2+ redox gate. A linear relationship between the anodic peak current and concentration of the analyte has been observed from 0 to 0.10 mmol L−1, with a nitrite detection limit of 7.60 μmol L−1