Journal of the American Chemical Society
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substituted tpy heads inside CB[8]), and thiol ligand exchanges
have reached an equilibrium. Supramolecular exchanges are at least
6 times faster than the fastest ligand exchange. Contrary to supra-
molecular exchanges, the kinetics of ligand exchanges strongly
depend on the size of the thiolate tail. For example, no ligand ex-
change is observed when the thiolate tail is L-glutathione (5).
CB[8]-secured Pt dimers undergo ligand exchange at least 1,700
times slower than CB[7]-bound Pt monomeric complexes. An
associative pathway that involves the formation of dimers of
CB[8]-secured Pt dimers (a total of 4 Pt complexes) has been
invoked to rationalize these trends.
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The thiolate tails also control the distribution of the 10 assemblies
at equilibrium. For example, we showed that “intra-assembly”
hydrogen bonding between L-cysteine units in assembly 4a2×CB[8]
favors narcissistic self-sorting, i.e. the retention of homoternary
complexes to the expense of their heteroternary counterparts. The
scope of this result is significant, as these CB[8]-secured Pt dimers
can now be used to quantify interactions between virtually any
dimer of cysteine-containing peptides. Furthermore, a library of n
Pt thiolates with different peptidic chains can present n(n+1)/2
pairs of peptides to targets of biological interest. The ease of the in
situ synthesis we report here thus constitutes an elegant method to
prepare vast dynamic libraries of potentially cytotoxic24–29 Pt(II)
complexes.
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ASSOCIATED CONTENT
Supporting Information
Preparation and characterization of Pt(II) complexes/CB[n] assem-
blies (PtCl·a)2·CB[8], (PtCl·b)2·CB[8], 1a2·CB[8], 2a2·CB[8],
1b2·CB[8] – 5b2·CB[8], 1a·CB[7], 1b·CB[7], 2a·CB[7] and
2b·CB[7]; protocol for kinetic experiments; computational data. The
Supporting Information is available free of charge on the ACS Publica-
tions website.
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AUTHOR INFORMATION
Corresponding Author
* masson@ohio.edu
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Henderson, R. A. Kinetics and Mechanism of Reactions of Transition
We are grateful to the National Science Foundation (grant CHE-
1507321), the American Chemical Society Petroleum Research
Fund (grant 56375-ND4), the Roenigk Family Foundation and
Ohio University for their continuing financial support. HB is also
supported by a fellowship from the Alfonso Martin Escudero
Foundation.
Metal Complexes; Wiley-VCH Verlag GmbH
& Co. KGaA:
Weinheim, 2002.
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Jordan, R. B. Reaction Mechanisms of Inorganic and Organometallic
Systems; Oxford University Press: Oxford, 2007.
Bugarčić, Ž. D.; Heinemann, F. W.; Van Eldik, R. Substitution
Reactions of [Pt(Terpy)X]2+ with Some Biologically Relevant
Ligands. Synthesis and Crystal Structure of [Pt(Terpy)(Cyst-
S)](ClO4)2·0.5H2O
and
[Pt(Terpy)(Guo-
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