Syntheses, characterization and electrochemical and spectroscopic properties of ruthenium-iron complexes of 2,3,5,6-tetrakis(2-pyridyl)pyrazine and ferrocene-acetylide ligands.

Abstract

Heterodimetallic Ru-Fe complexes [(tppz)(PPh3)2RuL](ClO4) (L = C[triple bond, length as m-dash]CFc, [](ClO4); C[triple bond, length as m-dash]C-C6H4-C[triple bond, length as m-dash]CFc), [](ClO4); C[triple bond, length as m-dash]C-C6H4-C6H4-C[triple bond, length as m-dash]CFc, [](ClO4)) were synthesized by the reactions of [(tppz)(PPh3)2RuCl](ClO4) (tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine) with ferrocence-acetylide ligands and characterized by ESI-MS, and (1)H and (31)P NMR spectroscopies. The structure of [](PF6) was determined by X-ray crystallography. The electrochemical studies show that compounds [](ClO4)-[](ClO4) possess two widely separated anodic peaks, ascribable to one-electron oxidation of Fc and Ru(II), respectively. This assignment is further corroborated by the results of UV-vis-NIR, XPS, and theoretical calculation studies. Compound [](ClO4) exhibits significant RuFe metal-metal interactions across the Ru-C[triple bond, length as m-dash]C-Fc backbone. As revealed by electrochemical, spectroscopic and theoretical computational studies, one-electron oxidized species [](ClO4)2 is between the electronically delocalized and valence-trapped state and shows a typical Robin-Day class II mixed-valence behavior.