Issue 3, 2007
From the journal:

Dalton Transactions

π–π Stacking assisted binding of aromatic amino acids by copper(ii)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability†

Tatsuo Yajima,a   Reiko Takamido,b   Yuichi Shimazaki,c   Akira Odani,d   Yasuo Nakabayashia  and  Osamu Yamauchi*a  

* Corresponding authors

a Unit of Chemistry, Faculty of Engineering, Kansai University, Suita, Osaka, Japan
E-mail: osamuy@ipcku.kansai-u.ac.jp

b Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan

c Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka, Japan

d Research Center for Materials Science, Nagoya University, Nagoya, Japan

Abstract

Ternary Cu(II) complexes containing an aromatic diimine (DA = di(2-pyridylmethyl)amine (dpa), 4,4′-disubstituted 2,2′-bipyridine (Y2bpy; Y = H (bpy), Me, Cl, N(Et)2, CONH2 or COOEt) or 2,2′-bipyrimidine) and an aromatic amino acid (AA = L-phenylalanine (Phe), p-substituted phenylalanine (XPhe; X = NH2, NO2, F, Cl or Br), L-tyrosine (Tyr), L-tryptophan (Trp) or L-alanine (Ala)) were characterized by X-ray diffraction, spectroscopic and potentiometric measurements. The structures of [Cu(dpa)(Trp)]ClO4·2H2O and [Cu((CONH2)2bpy)(Phe)]ClO4·H2O in the solid state were revealed to have intramolecular π–π interactions between the Cu(II)-coordinated aromatic ring moiety, Cu(DA) (Mπ), and the side chain aromatic ring of the AA (Lπ). The intensities of Mπ–Lπ interactions were evaluated by the stability constants of the ternary Cu(II) complexes determined at 25 °C and I = 0.1 M (KNO3), which revealed that the stability enhancement of the Cu(DA)(AA) systems due to the interactions is in the order (CONH2)2bpy < bpy < Me2bpy < (Et2N)2bpy with respect to DA. The results indicate that the electron density of coordinated aromatic diimines influences the intensities of the stacking interactions in the Cu(DA)(AA) systems. The Mπ–Lπ interactions are also influenced by the substituents, X, of Lπ and are in linear relationship with their Hammett σp values with the exception of X = Cl and Br.

Graphical abstract: π–π Stacking assisted binding of aromatic amino acids by copper(ii)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability

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Article information

DOI
https://doi.org/10.1039/B612394E
Article type
Paper
Submitted
29 Aug 2006
Accepted
26 Oct 2006
First published
08 Nov 2006

Dalton Trans., 2007, 299-307

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π–π Stacking assisted binding of aromatic amino acids by copper(II)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability

T. Yajima, R. Takamido, Y. Shimazaki, A. Odani, Y. Nakabayashi and O. Yamauchi, Dalton Trans., 2007, 299 DOI: 10.1039/B612394E

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