Preparation, characterization and electrochemical properties of ruthenium carbonyl octaethylporphyrins with axial quinoline and quinine ligands

The six-coordinate ruthenium(II) porphyrin complexes (OEP)Ru(CO)(Q), (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinato dianion; Q = quinoline, Qnl (2); quinine, QN (3)) have been prepared from (OEP)Ru(CO) (1) and characterized by MS, IR, UV–visible and ¹H NMR spectroscopy. The X-ray crystal structure of 2 has been determined, which reveals quinoline coordination to Ru through the nitrogen atom. In the crystal packing of 2, the two Qnl groups of adjacent porphyrins are positioned relatively parallel to each other at a close distance of 3.30 Å, implying a relatively strong π-π interaction. The X-ray crystal structure of 1 was obtained, which revealed coordination of the water to the ruthenium center. By comparing the spectroscopic data for 1, 2 and 3, it was determined that the site of binding of QN to Ru is likely through the nitrogen atom of the quinoline moiety. The redox behavior of the complexes at a Pt working electrode studied in a CH₂Cl₂ solution with NBu₄PF₆ as support electrolyte by cyclic voltammetry revealed oxidations that are porphyrin-centered.

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