| Abstrakt: |
With the aim of developing new IRdetectable metal–carbonyl tracers for the amino function, we have synthesized WCO5complexes of 4oxo42,5dimethylazaferrocen1′ylbutanoic acid 2 and 5oxo52,5dimethylazaferrocen1′ylpentanoic acid 3 by AlCl3catalyzed Friedel–Crafts reaction of WCO5–2,5dimethylazaferrocene 1 with succinic or glutaric anhydride. Complexes 2and 3are thermally stable and display sharp, intense absorption bands of tungstencoordinated CO ligands at ca. 1923 cm–1. In the crystalline state, molecules of 2and 3are stabilized by a network of intra and intermolecular hydrogen bonds, as shown by singlecrystal Xray structure analysis. Complex 2was transformed into the corresponding Nsuccinimidyl ester 4. Its utility toward labeling of amino acids was tested in its reaction with glycine methyl ester. Corresponding glycine amide 5was obtained in 82 yield and is an airthermally stable bioconjugate exhibiting intense sharp absorption bands of the W–CO reporting group at ca. 1923 cm–1. Cyclic voltammetry of 1, 2, 3, and acetyl derivative 6shows the presence of two redox events in each case. The first redox couple is ascribed as an azaferrocenecentered oxidation–reduction, whereas the second, irreversible process at higher potential originates from a WCO5centered oxidation. FTIR spectroelectrochemistry allowed us to monitor the spectroscopic changes accompanying the 11·+, 22·+, and 66·+redox transformations. Significant W–CO absorption band shifts were recorded in the course of these experiments.© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009 |
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