Stabilities of cubane type [Fe₄S₄(SR)₄](2-) clusters in partially aqueous media

The stability of cubane-type [Fe₄S₄(SR)₄](2-) clusters in mixed organic/aqueous solvents was examined as an initial step in the development of stable water-soluble cluster compounds possibly suitable for reconstitution of scaffold proteins in protein biosynthesis. The research involves primarily spectrophotometric assessment of stability in 20-80% Me₂SO/aqueous media (v/v), from which it was found that conventional clusters tend to be stable for up to 12h in 60% Me₂SO but are much less stable at higher aqueous content. α-Cyclodextrin mono- and dithioesters and thiols were prepared as ligand precursors for cluster binding, which was demonstrated by spectroscopic methods. A potentially bidentate cyclodextrin dithiolate was found to be relatively effective for cluster stabilization in 40% Me₂SO, suggesting (together with earlier results) that other exceptionally large thiolate ligands may promote cluster stability in aqueous media.