Optically active 4- and 5-coordinate transition metal complexes of bifurcated dipeptide Schiff bases

Robin Polt, Brian D. Kelly, Brian D. Dangel, Udaya Bhaskar Tadikonda, Regina E. Ross, Arnold M. Raitsimring, Andrei V. Astashkin

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Symmetrical and unsymmetrical benzophenone Schiff bases of bifurcated dipeptides [e.g., Ar2C=N-CHR1CONH∼HNCO-CHR2-N= CAr2] have been synthesized using Boc methodology. These ligands may be regarded as chiral porphyrin mimics because of the α-carbons of the amino acids. The Schiff bases function as effective ligands for transition metals, particularly the late transition metals Ni(II), Cu(II), and Zn. Upon metal insertion, there is loss of the amide protons, resulting in N4 chelating ligands that retain the amino acid based chirality as well as newly generated metal-centered chirality, which for the Ni(II) complexes have been shown by X-ray analysis to be A (left-handed helix) if the amino acids are S. For Ni(II) and Cu(II), metal insertion results in highly colored complexes and is easily followed by UV-vis spectrophotometry. Several Ni(II) complexes were also characterized by 1H NMR. Co(II) and Mn(II) complexes were characterized by CW EPR. Two Cu(II) complexes, 7f-CuII and 7k-CuII, were characterized by EPR (ENDOR and ESEEM), which clearly showed the pentacoordinate nature of 7k-CurrII.

Original languageEnglish (US)
Pages (from-to)566-574
Number of pages9
JournalInorganic Chemistry
Issue number2
StatePublished - Jan 27 2003

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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