Synthesis and Characterization of Cu II Complexes with Amino Acid Substituted Di(2‐pyridyl)amine Ligands

The two‐step syntheses of the substituted di(2‐pyridyl)amine ligands (dpa), dpa‐CH 2 CO 2 H ( 1 ) and dpa‐PhCO 2 H ( 2 ), are described. Ligands 1 and 2 are successfully coupled to the amino acid phenylalanine, yielding the derivatives 4 and 6 , respectively. Four Cu II (dpa) 2 complexes, [Cu(dpa‐CH 2 CO 2 t Bu) 2 (NO 3 ) 2 ] ( 3 Cu ), [Cu(dpa‐CH 2 CO‐PheOMe) 2 (H 2 O) 2 ](NO 3 ) 2 · 2MeOH ( 4 Cu ), [Cu(dpa‐PhCO 2 Me) 2 (MeOH) 2 ](ClO 4 ) 2 ( 5 Cu ) and [Cu(dpa‐PhCO‐PheOMe) 2 (ClO 4 ) 2 ] ( 6 Cu ) have been prepared and characterized, including their single crystal X‐ray structures. Fluorescence emission at UV (for 3 and 4 ) or blue (for 5 and 6 ) wavelengths of the free ligands is preserved in the corresponding Cu complexes, although with lower intensity. X‐band EPR spectra of 4 Cu and 6 Cu both revealed one axial Cu II signal with hyperfine and superhyperfine splittings. Complexes 4 Cu and 6 Cu are chiral inorganic complexes with amino acid bioconjugates that may serve as nucleoside analogs in modified peptide nucleic acids (PNA). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)