Interaction of Methimazole with I2: X-ray Crystal Structure of the Charge Transfer Complex Methimazole−I2. Implications for the Mechanism of Action of Methimazole-Based Antithyroid Drugs

The antithyroid drug methimazole (MMI) reacts with molecular iodine to form, in a multistep process, 1-methylimidazole as final product. In this process, the charge transfer complex MMI−I2 and the ionic disulfide [(C4H6N2S–)2]2+ (1, dication MMI disulfide) have been isolated and their X-ray crystal structures solved. Dication MMI disulfide perchlorate acts effectively both in reducing I2 to I− ions and in showing antioxidant properties in inactivating the enzyme lactoperoxidase compound I.