| Autor: |
Laurence, Christian, J. El Ghomari, Mohamed, Le Questel, Jean-Yves, Berthelot, Michel, Mokhlisse, Rachid |
| Zdroj: |
Journal of the Chemical Society, Perkin Transactions 2; July 1, 1998, Vol. 1998 Issue: 7 p1545-1552, 8p |
| Abstrakt: |
The anti-thyroid drug methimazole functions as a diiodine sponge. Its thione tautomer forms with diiodine a very stable electron donor–acceptor complex (Kf 4;= 4;36 4;600 l mol–1 in CCl4), stabilized in a more polar medium (Kf 4;= 4;92 4;400 l mol–1 in CH2Cl2). Two stereoisomeric complexes, one planar on the non-bonding sulfur lone pair and the other perpendicular on the sulfur π electrons, are found in solution to be under steric control. The position of the charge-transfer band of many diiodine complexes of thioamides and thioureas allows the prediction of their geometry. The sulfur–iodine coordination is assisted by intramolecular hydrogen bonding NH · 4;· 4;· I. This iodine amphoterism is explained by the anisotropy of its electrostatic potential surface. Hard and soft acid–base chemistry might explain the two mechanisms of action of anti-thyroid drugs, the inhibition of thyroid peroxidase via coordination to the hard heme group and the trapping of oxidized iodides via complexation of soft iodinated Lewis acids. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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