Triggering Cu-coordination change in Cu(ii)-Ala-His-His by external ligands.

Copper(ii) forms well-known and stable complexes with peptides having histidine at position 2 (Xxx-His) or 3 (Xxx-Zzz-His). Their properties differ considerably due to the histidine positioning. Here we report that in the hybrid motif Xxx-His-His, the Cu(ii)-complexes can be switched between the Xxx-His and the Xxx-Zzz-His coordination modes by addition of external ligands.