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

•Synthesis of new supermolecule ruthenium–porphyrin.•Spectroscopic studies of the ruthenium–porphyrin system.•Nitrite sensing by chronoamperometry.

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.

Graphical abstractRuthenium–porphyrins supermolecules are interesting system to be used as electroactive layer in chemically modified electrode in order to produce high performance molecular sensors. Obtained films have shown good stability and relevant electrocatalytic response for nitrite oxidation.Figure optionsDownload full-size imageDownload as PowerPoint slide