Manganese-Based Magnetic Superhalogens

摘要

The unusual properties of nanoscale materials brought about by their reduced sizes have ushered in a new era in materials science where materials with tailored properties can be synthesized. A fundamental understanding of how their properties evolve one atom and/or one electron at a time can be best studied with atomic clusters. Numerous studies of clusters over the past 30 years have demonstrated their unique properties, which can be tailored by fixing their size and composition. One of the most important properties of atomic clusters is that they exhibit unusual stability at a specific size and composition. There are two main classes of these stable clusters, which are often referred to as magic clusters. Clusters of simple metals such as sodium exhibit unusual stability at 2, 8, 18, 20, 34, 40, ... atoms, while clusters of noble gas atoms exhibit stability at 13, 55,147, ... atoms.The former series is due to electronic shell closure, while the latter is due to atomic shell closure. It has been suggested that magic clusters, owing to their enhanced stabilities, can forrn building blocks of new cluster assembled materials. Herein we present the discovery of a new class of magnetic magic clusters with molecular composition (Mn_xCl_(2x+1)~- (x = 1, 2, 3, 4, ...). Supported by photoelectron spectroscopy experiments and density functional theory (DFT)-based calculations, we show that these magic clusters owe their unusual stability neither to the conventional electronic shell closing nor to the atomic shell closing, but to the superhalogen character of their corresponding neutral species and to the d5 configuration of each of the manganese atoms. These molecular anions have the potential to serve as building blocks of a new class of salts with magnetic and super-oxidizing properties.