Abstract: Superhalogens exhibit special stable characters and electronic properties, and are suitable to be used as building blocks in designing cluster assembling materials. BO2 is only one electron short to electronic shell closing and has a high electron affinity, 446 eV, larger than that of halogen atoms, so BO2 can be considered as a superhalogen. In order to confirm this, the interactions between BO2 and Cu, Na atoms as well as microscopic salvation of NaBO2 cluster were intensively studied through anion photoelectron spectroscopy (PES) and density functional theory (DFT) calculation. The studies show that BO2 moiety still retains its linear structure as the bare BO2 cluster and behaves as a superhalogen. On the other hand, the microscopic solvation of NaBO2 in water is similar to that of halogen salts. NaBO2 appears as contact ion pair (CIP) structure at first, and then there is a significant change in the photoelectron spectra of NaBO2-(H2O)n clusters starting from n=3, corresponding to the transition from contact ion pair (CIP) structure to solvent-separated ion pair (SSIP) structure. Besides, with an electron affinity of 507 eV, which is larger than that of its BO2 superhalogen building-block, Cu(BO2)2 can be classified as a hyperhalogen. Since the hyperhalogen contains three different elements, it has much more freedom in designing materials.

Key words: anion photoelectron spectroscopy, density functional theory, superhalogens, cluster-assemble materials