Ac‐His‐OH and His‐His‐OH were treated with [Re(CO)3(H2O)3]+ to yield two new compounds, which were structurally characterized. Each displays a peptide carboxamido‐N donor. The complex formed with His‐His‐OH uses this group as a bridging, bidentate ligand; the complex resists challenge experiments showing that His‐tags are a good way to deliver the [M(CO)3]+ core (M = 99mTc, Re).
The cover picture shows the crystal structures of two complexes that were prepared from aqueous reactions of histidine‐based ligands with Re(CO)3(H2O)3+ and serve as models of 99mTc(CO)3+/His‐tag protein complexes. The complexes, similar to those found in certain enzymes, show unexpected peptide carboxamido‐N donor bonds that underscore the stability of the labeled His‐tag proteins as discussed in the Short Communication by R. S. Herrick, C. J. Ziegler et al. on p. 3905 ff. Artwork: Christopher J. Ziegler.
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