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First Zn(II) bowl-complexes modeling the tris(histidine) metallo-site of enzymes.

The bowl-shaped resorcin[4]arene-based ligand was prepared as a model of the trihistidine coordination core present in many mononuclear metalloenzymes. The -CH(2)-O-CH(2)- linkers connecting the imidazoles to the cavity allow three imidazoles to simultaneously bind a metal ion, and favor cis-coordination of two exchangeable ligands. The corresponding mononuclear Zn(II) complexes were shown to be capable of the selective guest binding and exchange at both endo and exo positions.