Book of Abstracts - Ruhr-Universität Bochum

OP-31
ISBOMC `10 5.7 – 9.7. 2010 Ruhr-Universität Bochum
Polypeptides Induced Self-Association and Emission Properties of
Platinum(II) and Gold(I) Complexes
Toshiyuki Moriuchi, *a Masahiro Yamada, a Kazuki Yoshii, a and Toshikazu Hirao a
a Department of Applied Chemistry, Graduate School of Engineering, Osaka University,
Yamada-oka, Suita, Osaka 565-0871, Japan. E-mail: moriuchi@chem.eng.osaka-u.ac.jp
Highly-ordered molecular assemblies are constructed in bio-systems to fulfill unique functions as
observed in enzymes, receptors, etc. Introduction of functional complexes into highly-ordered
biomolecules is considered to be a convenient approach to novel biomaterials, bio-inspired systems,
etc. Recently, the field of bioorganometallic chemistry has drawn great attention and undergone rapid
development. Conjuction of organometallic compounds with biomolecules such as peptides and
nucleobases is envisioned to afford such bioconjugates. The non-covalent bond is a powerful tool in
the construction of architectural molecular assemblies. We have already demonstrated the chirality
organization of ferrocene-peptide bioconjugates to induce highly-ordered molecular assemblies. 1
Poly-L-glutamic acid (P(Glu)) is known to exist in a �-helix form at around pH 4.3. The carboxyl
groups of side chains are expected to assemble cationic metal complexes along the exterior of poly-Lglutamic
acid through the electrostatic interactions. On the other hand, poly-L-Lysine (P(Lys)) exists
as a random coil conformation at a neutral pH due to repulsion between positively charged side chains,
and an �-helical conformation at above pH 10.6 due to the reduced charge on the side chains at a pH
above the pKa (10.5). P(Lys) bearing multiple positively charged side chains is envisioned to serve as a
polymeric spatially aligned scaffold for the aggregation of negatively charged metal complexes. From
these points of view, we embarked upon the assembling and self-association of luminescent metal
complexes spatially along the cationic or anionic polypeptides to form the luminescent aggregates.
The cationic organoplatinum(II) complexes
[Pt(trpy)C≡CR] + (trpy = 2,2',6',2''-terpyridine; R = Ph
(PtH), PhC12H25 (PtC12)) were introduced into the anionic
poly-L-glutamic acid (P(Glu)) through electrostatic
interactions. An emission based on metal-metal-to-ligand
charge transfer (MMLCT) transition was observed in the
case of P(Glu)-PtC12. However, such synergistic effect
was not observed in the case of P(Glu)-PtH. Poly-L-
glutamic acid was found to serve as an efficient molecular scaffold, wherein the platinum(II)
complexes might be accommodated.
The assembling and self-association of anionic dicyanoaurate(I), [Au(CN)2] � , spatially around the
cationic poly-L-Lysine (P(Lys)) through electrostatic interactions was also demonstrated to form the
luminescent [Au(CN)2] � aggregates.
References
1. (a) Chem. Commun. 1998, 1963. (b) J. Organomet. Chem. 1999, 589, 50. (c) J. Am. Chem. Soc.
2001, 123, 68. (d) Organometallics 2001, 20, 1008. (e) Organometallics 2001, 20, 3101. (f) J.
Organomet. Chem. 2001, 637-639, 75. (g) Org. Lett. 2003, 5, 4285. (h) Org. Lett. 2005, 7, 5265. (i)
Org. Lett. 2006, 8, 31-34. (j) Dalton Trans. 2009, 4286.
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