Synthesis and characterization of monometallic and bimetallic mixed-ligand complexes of iron(II) containing 2,2'-bipyrimidine or 2,3-bis(2-pyridyl)pyrazine

Abstract

Mono- and bimetallic complexes of the form Fe(CN)/sub 4/BL/sup 2 -/ and (Fe(CN)/sub 4/)/sup 2/(BL)/sup 4 -/, where BL = 2,2'-bipyrimidine (bpm) or 2,3-bis(2-pyridyl)pyrazine (dpp), have been prepared and characterized by column chromatography, uv-visible spectroscopy, cyclic voltammetry, and coulometry. The complexes are stable in aqueous solution and have electronic spectra dominated by intense metal-to-ligand charge-transfer (MLCT) transitions in the visible region of the spectrum. The maximum for the lowest energy MLCT peak in the monometallic complexes is in the 530-550-nm region while the bimetallic complexes, with an increased stability of the ..pi.. orbitals on BL, show maxima in the 580-660-nm region. The monometallic complexes display one reversible oxidation corresponding to the Fe(III/II) couple, while two reversible oxidations, separated by 140-150 mV, are observed for the bimetallic complexes. 34 references, 2 figures, 2 tables.