Photoelectron spectroscopy of transition metal-sulfur cluster anions

Abstract

Metal (M)-sulfur cluster anions (M = Ag, Fe and Mn) have been studied using photoelectron spectroscopy (PES) with a magnetic-bottle type time-of-flight electron spectrometer. The MnSm− cluster anions were formed in a laser vaporization cluster source. For Ag-S, the largest coordination number of Ag atoms (nmax) is generally expressed as nmax =2m − 1 in each series of the number of S atoms (m). For Fe−S and Mn−S, it was found that the stable cluster ions are the ones with compositions of n=m and n=m±1. Their electron affinities were measured from the onset of the PES spectrum. For Ag−S, the EAs of Ag1Sm are small and around 1 eV, whereas those of AgnSm (n ≥ 2) become large above 2 eV. The features in the mass distribution and PES suggest that Ag2S unit is preferentially formed with increasing the number of Ag atoms. For Fe−S and Mn−S, the PES spectra of FenSm−/MnnSm− show a unique similarity at n ≥ m, indicating that the Fe/Mn atom addition to FenSn−/MnnSn− has little effect on the electronic property of FenSn/MnnSn. The PES spectra imply that the FenSn cluster is the structural framework of these clusters, as similarly as the determined structure of the FenSn cluster in nitrogenase enzyme.