Addition of (Pyrazol‐1‐yl)acetyl and (Pyridin‐2‐yl)acetyl Groups to the Terminal Amino Group of a Phe−Gly Dipeptide Affords ATCUN‐Like Copper( II ) Binding Sites

(Pyrazol‐1‐yl)acetic acid (HL 1 , 1 ) and (pyridin‐2‐yl)acetic acid have been successfully condensed with the terminal amino group of a Phe−Gly dipeptide to generate the derivatives PzCH 2 –Phe−Gly (H 3 L 2 , 7 ) and PyCH 2 –Phe−Gly (H 3 L 3 , 8 ) respectively, which contain ATCUN‐like metal ion binding sites. The crystal structures of 1 and the copper( II ) complexes Cu(L 1 ) 2 (H 2 O) 2 ( 2 ) and [ n Bu 4 N][Cu(L 2 )] ( 9 ) are described. Complex 2 has a tetragonally‐elongated, Jahn–Teller distorted octahedral geometry and complex 9 is square‐planar. The structural similarity of the copper( II ) complexes of 7 and 8 is demonstrated by their almost identical electronic absorption and EPR spectra. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)