Abstract

The discovery in 1971 of the high critical field superconducting properties of Chevrel phases with transition temperatures T-c between 10 and 18 K stimulated extensive research to improve their superconducting behavior. This fact was also the starting point for a new research area in solid-state and molecular chemistry involving the Mo-6 and Re-6 clusters where the intercluster bonding interactions seen in the solid phases are lacking, so a more localized cluster wave function at the Fermi level arises, as suggested by Fischer in 1978. Here, we describe the bonding, optical, magnetic, redox, and biological properties of related hexanuclear species given by M-6(Q, X)(8)L-6 (M = Mo, W, Re; Q = S, Se, Te; X = Cl, Br, I; and L = sigma or pi ligand) molecular clusters. Noteworthy, cancer cells are more sensitive to [Re6Se8I6](3-) cluster-induced cell death than normal cells. The molecular view of such species offers a fresh perspective enabling further rational design of building blocks for interesting materials.