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···π 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-S Cys29 bonds with stabilization afforded by a combination of N-H···π, C-H···π and Cl vinyl···H interactions. These results comparable favorably with known inhibitors of cathepsin B suggesting the title compounds have potential biological activity.
organotellurium-dihalides; docking studies; cathepsin B; crystal structures; supramolecular arrangements
