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Spectroscopic and Electrochemical Investigations into the Interactions of Metal Ions with a Ferrocenoyl–Histidine Peptide Conjugate
Author(s) -
Cheng LanYa,
Long YiTao,
Tian He,
Kraatz HeinzBernhard
Publication year - 2010
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201000658
Subject(s) - chemistry , conjugate , ferrocene , metal , imidazole , cyclic voltammetry , metal ions in aqueous solution , crystallography , electrochemistry , nuclear magnetic resonance spectroscopy , inorganic chemistry , stereochemistry , organic chemistry , electrode , mathematical analysis , mathematics
A new ferrocene–peptide conjugate Fc‐[His(DNP)‐Gly‐OMe] 2 ( 2 ) was synthesized and characterized spectroscopically. The conjugate displays the familiar 1,2′‐ P helical Herrick conformation in solution and exhibits a reversible one‐electron oxidation at 380 mV versus Fc/Fc + . The interactions of the metal ions Na + , Mg 2+ , Fe 2+ , Cu 2+ , Zn 2+ , and Cd 2+ with conjugate 2 were probed by using a range of techniques, including cyclic voltammetry, and NMR and CD spectroscopies. Electrochemical studies showed that the system exhibits a rare cathodic potential shift upon the addition of metal ions, which followed the order Cu 2+ (–436 mV) > Fe 2+ (–284 mV) > Zn 2+ (–270 mV) > Cd 2+ (–238 mV) > Mg 2+ (–180 mV) > Na + (–75 mV). The formation of a 1:1 metal complex was postulated on the basis of CV and NMR spectroscopic titration experiments. The complexes themselves were characterized by electrospray mass spectrometry. NMR spectroscopic studies show that the His imidazole is the site of metal coordination. As is confirmed by CD spectroscopy, metal coordination itself results in conformational changes of the ferrocene core that are dependent on the particular metal ion and its coordination preferences. Whereas P ‐helicity of the conjugate is maintained during the interactions with Mg 2+ , Zn 2+ , and Cd 2+ , M ‐helicity is adopted for Fe 2+ and Cu 2+ .