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Triplet state properties of the methylmercury(II)-tyrosine complex
Authors:Martin V. Hershberger  August H. Maki
Affiliation:Department of Chemistry, University of California at Davis, USA
Abstract:CH3Hg(II)OH forms complexes at pH 8 with tyrosine and with tyrosine ethyl ester (TEE) that are detected by ultraviolet difference absorption spectra. With Kf defined by CH3HgOH + HB
/></figure> CH<sub>3</sub>HgB + H<sub>2</sub>O, we find log <em>K</em><sub><em>f</em></sub> = 3.61 (tyrosine) and 3.36 (TEE). A heavy-atom effect is observed in frozen glasses of the complexes; this indicates a close interaction between Hg and the chromophore. No UV difference spectrum or heavy-atom effect is observed with <em>N</em>-acetyl tyrosine ethyl ester, indicating that complexing at the phenol O does not occur, and suggesting that binding occurs at the amine N. Zero field optically detected magnetic resonance (ODMR) measurements of the CH<sub>3</sub>Hg(II)-tyrosine triplet state give (D, E) = (0.129, 0.047) or (0.134, 0.041) cm<sup>?1</sup> depending upon assignment of transitions. D of tyrosine is relatively unaffected, but E is reduced by CH<sub>3</sub>Hg(II) complexing. Low-temperature kinetic measurements show that the shortest lived sublevel of the complex is T<sub><em>z</em></sub>, where <em>z</em> lies along the phenol long axis in tyrosine. A dominant 11.6-msec component in the 77 K decay of the phosphorescence is consistent with the individual sublevel lifetimes obtained by ODMR.</td> </tr> <tr> <td align=
Keywords:Address reprint requests to: Dr. A. H. Maki   Department of Chemistry   University of California   Davis   CA 95616   USA.
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