Silicon (Si), germanium (Ge), tin (Sn), and lead (Pb) clusters mixed with a group-4 transition metal atom [M=titanium (Ti), zirconium (Zr), and hafnium (Hf)] were generated by a dual-laser vaporization method, and their properties were analyzed by means of time-of-flight mass spectroscopy and anion photoelectron spectroscopy together with theoretical calculations. In the mass spectra, mixed neutral clusters of M Si16, M Ge16, and M Sn16 were produced specifically, but the yield of M Pb16 was low. The anion photoelectron spectra revealed that M Si16, M Ge16, and M Sn16 neutrals have large highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of 1.5-1.9 eV compared to those of M Pb16 (0.8-0.9 eV), implying that M Si16, M Ge16, and M Sn16 are evidently electronically stable clusters. Cage aromaticity appears to be an important determinant of the electronic stability of these clusters: Calculations of nucleus-independent chemical shifts (NICSs) show that Si16 4-, Ge16 4-, and Sn16 4- have aromatic characters with negative NICS values, while Pb16 4- has an antiaromatic character with a positive NICS value.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry