Synthesis and properties of diiron complexes with heteroaromatic linkers: An approach for modulation of organometallic molecular wire

Metal complexes with two redox active organometallic Cp∗(dppe)FeCC units bridged with N-methylpyrrole (3), furan (4) and dipyrrolylethene (6) have been synthesized and characterized by 1H and 31P NMR, IR and ESI-MS spectroscopy as well as X-ray diffraction study (for 3). Cyclic voltammograms of 3 and 4 show two reversible redox waves ascribed to iron centered redox processes, and the comproportionation constants (KC) of their mixed valence species were determined to be 5.8 × 106 and 1.0 × 106, respectively. UV–Vis–NIR spectra of 3+ and 4+ contain intense absorption bands in the NIR region ascribed to intervalence charge transfer processes. The complexes with electronic coupling (Vab) values of 2950 (3) and 2665 cm−1 (4) were classified as class III compounds according to the Robin–Day classification. These data suggest that the electronic interaction between the two iron centers is stronger than those of the p-phenylene and thienylene derivatives. Complex 6, a pyrrole analogue of the photochromic dithienylethene complexes, turns out not to show photochromic behavior, indicating that the heteroaromatic component influenced significantly on photochromic behavior.

Molecular wires with two redox active organometallic Cp∗(dppe)Fe(CC units bridged with various heteroaromatic linkers have been synthesized. Heteroatoms in the molecular wires play important roles in controlling electron transfer between metal termini.Figure optionsDownload as PowerPoint slide