1. Wei-Li Li, Constantin Romanescu, and Lai-Sheng Wang Chemistry Dept., Brown Univ., Providence, RI, 02912 06-19-2012

2. J. Phys. Chem. A 107, 1359 (2003); 107, 9319 (2003); 108, 3509 (2004); Angew. Chem. Int. Ed. 107, 9319 (2003); Nature Mat. 2, 827 (2003); Inorg. Chem. 43, 3552 (2004); J. Chem. Phys. 122, 054313 (2005), 134, 224304 (2011); PNAS 102, 961 (2005); JACS 130, 7244 (2008); Nature Chem. 2, 202 (2010) Boron clusters anions (B n - ) have planar or quasi-planar structures at least up to n = 21; The highest coordination number observed experimentally is 8 (B 9 - ); 20 21

3. They are aromatic, but not planar. II (C 2v, 1 A 1 ) antiaromatic I (C 6v, 3 A 1 ) aromatic B7–B7– B7–B7– B 12 (C 3v, 1 A 1 ) aromatic B 12

4. Will the planar structures be favored by expanding the peripheral ring?

5. Compare the VDEs with the computed VDEs of the several lowest energy isomers, decide the isomer(s) that correspond to the spectra.

6. 532 nm Variable detached laser energies: Higher energy reveals more transition bands; Lower energy resolves features better (ΔK E /K E =2.5%).

7. AlB 6 – B7–B7– Alexandrova, A. N. et al., JPCA 2004, 108, 3509.Romanescu, C. et al., JACS 2011, 133, 8646

8. Conflicting aromaticity: - 6 delocalized  electrons:  - aromaticity - 4 delocalized  electrons:  - antiaromaticity C 8 H 8 : antiaromatic Release the strain to stabilize planar structure.

9. AlB 11 – Zhai, H. J. et al., Nature Materials 2003, 2, 827. B 12 – AlB 11 –

10. Doubly aromatic system: - 2 sets of delocalized  bonds (2 + 10 electrons): 2 *  aromaticity - 2 sets of delocalized  bonds (4 + 2 electrons): 2 *  aromaticity

11. The Al + ionically bonds to the B 11 2– cluster; B 11 2– is both  and  aromatic.

12. Aluminum substitution expands the outside ring and stabilizes the planar cluster.

13. B 9 - ( 1 A 1g, D 9h )B 8 2- ( 1 A 1g, D 8h )

14. PES of AlB 7 – and AlB 8 – at 266 nm and 193 nm Galeev, T.R. et al., JCP. 2011, 135, 104301

15. PES of AlB 9 – and AlB 10 – at 266 nm and 193 nm Relative energies are given at the RCCSD(T)/6-311+G(2df)//B3LYP/6-311+G* and the B3LYP/6-311+G* (in brackets) levels of theory. Li, W. L. et al., JPCA. 2011, 115, 10391

16. Aluminum prefers to stay on the peripheral position and forms ionic bonds with the boron counter-ions. Transition metals might be better candidates for wheel type clusters.

17. Prof. Lai-Sheng Wang Constantin Romanescu Timur R. Galeev Prof. Alexander I. Boldyrev Brown University Alina P. Sergeeva Boldyrev’s group (Utah State Univ., Logan, UT) Wang’s group (Brown Univ.)