Valence self-regulation of sulfur in nanoclusters.

The valence self-regulation of sulfur from the "-2" valence state in thiols to the "-1" valence state in hydroxylated thiolates has been accomplished using the Pt1Ag28 nanocluster as a platform-the first time that the "-1" valent sulfur has been detected as S-1. Two previously unknown nanoclusters, Pt1Ag28(SR)20 and Pt1Ag28(SR)18(HO-SR)2 (where SR represents 2-adamantanethiol), have been synthesized and characterized-in the latter nanocluster, the presence of hydroxyl induces the valence regulation of two special S atoms from "-2" (in SR) to "-1" valence state in the HO-S(Ag)R. Because of the contrasting nature of the capping ligands in these two nanoclusters [i.e., only SR in Pt1Ag28(SR)20 or both SR- and HO-SR- in Pt1Ag28(SR)18(HO-SR)2], they exhibit differing shell architectures, even though their cores (Pt1Ag12) are in the same icosahedral configuration. Single-crystal x-ray diffraction analysis revealed their 1:1 cocrystallization, and mass spectrometry verified the presence of hydroxyls on Pt1Ag28(SR)18(HO-SR)2.