Heterometallic ferrocene-rhenium complexes linked by an aminoethylglycine scaffold

Using mono- and 1,n′-disubstituted ferrocenecarboxylic acid, the aminoethylglycine (aeg) derivatives Fe[C₅H₄-CO-aeg-OtBu] [C₅H₅] (1) and Fe[C₅H₄-CO-aeg-OtBu] ₂ (2) have been synthesized. Complexes 1 and 2 are further reacted to substitute the aeg with the nitrogen-containing ligands dpa-ph-CO₂H or py-AcOH to yield complexes 3-6. Each of these is treated with Re(CO) ₅Cl to assemble heterometallic structures 3_Re-6 _Re. These are subsequently isolated and characterized by NMR and mass spectrometry, FTIR, UV/Vis absorbance, and fluorescence emission spectroscopy, and separately by electrochemistry. All of the compounds exhibit the characteristic redox properties of the ferrocene moiety; in the heterometallic compounds, an irreversible oxidative wave is attributed to the Re. The electrochemically determined diffusion coefficients of the compounds confirm that the as-prepared structures are discrete assemblies and not coordination polymers.