2-Chlorovinyl Tellurium Dihalides, (p-tol)Te[C(H)=C(Cl)Ph]X2 for X = Cl, Br and I: Variable Coordination Environments, Supramolecular Structures and Docking Studies in Cathepsin B

Abstract

Crystallography shows that the Te atom in each of (p-tol)Te[C(H)=C(Cl)Ph] X2, for X = Cl (1), Br (2) and I (3), is within a distorted ψ-pentagonal bipyramidal geometry. An E configuration for the vinyl group in (1) precludes the formation of an intramolecular Te⋯Cl interaction so that an intramolecular Te⋯p interaction is found instead. The coordination environment features a linear Cl-Te-Cl arrangement with the pentagonal plane defined by the two C atoms of the organic substituents, an intermolecular Te⋯Cl contact, a Te⋯π interaction and a stereochemically active lone pair of electrons. In the X = Br (2) and I (3) structures, similar coordination geometries are found but the Te⋯π contact is replaced by an intramolecular Te⋯Cl contact owing to the adoption of a Z configuration about the vinyl bond. The differences in structure are readily explained in terms of electronic effects. Docking studies of cathepsin B with (1')-(3'), i.e. 1-3 less one Te-bound halide, show efficient binding through the agency of covalent Te-SCys29 bonds with stabilization afforded by a combination of N-H⋯π, C-H⋯π and Clvinyl⋯H interactions. These results comparable favorably with known inhibitors of cathepsin B suggesting the title compounds have potential biological activity. © 2010 Sociedade Brasileira de Química.