Ab initio molecular orbital theory and density functional theory have been applied to investigate LiB7 and BeB7+ species. Almost the same stability order as bare B-7(-) occurs for both LiB7 and BeB7+ species, two low-lying (C-6v, (3)A(1)) and (C-2v, (1)A(1)) structures are the lower energy minima. Natural bond orbital (NBO) and molecular orbital (MO) analyses show that the B-7(-) unit in LiB7 and BeB7+ is nearly identical to the pure B-7(-) cluster, providing a viable possibility to use it as a novel ligand and building unit. (c) 2006 Elsevier B V. All rights reserved.