Towards a custom chelator for mercury: evaluation of coordination environments by molecular modeling

Abstract  

A chelator is a molecule which binds a metal or metalloid ion by two or more functional groups to form a stable ring complex known as a chelate. Despite the widespread clinical use of so-called chelation therapy to remove mercury, none of the drugs currently in use have been shown to chelate mercury. Mercury can adopt three common coordination environments: linear diagonal, trigonal planar, and tetrahedral. We have previously discussed some of the structural criteria for optimal binding of mercury in linear-diagonal coordination with thiolate donors (George et al. in Chem. Res. Toxicol. 17:999–1006, 2004). Here we employed density functional theory and X-ray absorption spectroscopy to evaluate the ideal chain length for simple alkane dithiolate chelators of Hg²⁺. We have also extended our previous calculations of the optimum coordination geometries to the three-coordinate Hg(SR)₃]⁻ case. Finally, we propose a new chelator “tripod” molecule, benzene-1,3,5-triamidopropanethiolate, or “Trithiopod,” which is expected to bind Hg²⁺ in three-coordinate geometry with very high affinity.