Synthesis, characterization, and radical scavenging effects of polynuclear thiolate complexes

Three thiolate complexes (Me4N)2[M4(o-SC6H4CH3)10], [M=Zn (1); Cd (2)] and [c-μ4-S)(SCH2Ph)12S4Zn8] (3) were synthesized and characterized by elemental analyses, IR, and 1H NMR spectroscopic techniques. The suppression abilities of complexes for the hydroxyl radical (OH·) and TEMP (HO-N-O·) were determined by EPR. The former were also measured by its reaction with 3-methylthiobutyraldehyde (MBA) to give propylene and methane analyzed by GC. The results show that the complexes possess selectively scavenging effects: on the hydroxyl radicals, abilities decreased across the series 3>NMT>2 ≈ 1 (NMT=native metallothionein), whereas, on TEMP radicals, the order was 1>3>NMT>2.