Molecular wheel B82- as a new inorganic ligand.: Photoelectron spectroscopy and ab initio characterization of LiB8-

The bare B-8 cluster was previously reported to be a D-7h molecular wheel with a triplet group state. The B-8(2-) dianion was predicted to be a closed-shell singlet and double aromatic D7h molecular wheel. Here we report the experimental observation of B-8(2-) stabilized by a Li+ cation in LiB8- and its experimental characterization using photoelectron spectroscopy. Theoretical searches lead to a C-7v LiB8- global minimum structure, and its calculated photodetachment transitions are in good agreement with the experimental values. Except for a small out-of-plane distortion due to the asymmetric Li+ capping, the B-8(2-) unit in LiB8- is nearly identical to the bare B-8(2-), suggesting it is a robust and stable structural unit and may be used as a new ligand and building block in chemistry.