Spin conservation accounts for aluminum cluster anion reactivity pattern with O2.
The reactivity pattern of small (approximately 10 to 20 atoms) anionic aluminum clusters with oxygen has posed a long-standing puzzle. Those clusters with an odd number of atoms tend to react much more slowly than their even-numbered counterparts. We used Fourier transform ion cyclotron resonance mass spectrometry to show that spin conservation straightforwardly accounts for this trend. The reaction rate of odd-numbered clusters increased appreciably when singlet oxygen was used in place of ground-state (triplet) oxygen. Conversely, monohydride clusters AlnH-, in which addition of the hydrogen atom shifts the spin state by converting formerly open-shell structures to closed-shell ones (and vice versa), exhibited an opposing trend: The odd-n hydride clusters reacted more rapidly with triplet oxygen. These findings are supported by theoretical simulations and highlight the general importance of spin selection rules in mediating cluster reactivity.
Burgert
R
R
Institute of Inorganic Chemistry, University of Karlsruhe (TH), 76128 Karlsruhe, Germany.
Schnöckel
H
H
Grubisic
A
A
Li
X
X
Stokes
S T
ST
Bowen
K H
KH
Ganteför
G F
GF
Kiran
B
B
Jena
P
P