The 2Fo-Fc electron density map showed a single intense peak adjacent to the BpyAla bipyridine corresponding to a Cu(II) ion coordinated to N1 and N2 of BpyAla (Cu-N bond distance of 2 Å) and four water molecules in an octahedral arrangement (Figure in ESIa). The B-factors for the Bpy moiety and the Cu(II) ion (43 Å 2 and 57.91 Å 2 , respectively) were lower in this structure compared to the bipyridine rings in the Cu(II)-bound Q111CBipy structure, indicating that the catalytic environment is more rigid.