Superhalogens belong to a class of molecules that not only mimic the chemistry of halogen atoms but also possess electron affinities that are much larger than that of chlorine, the element with the highest electron affinity in the periodic table. Using BO 2 as an example and the synergy between density functional theorybased calculations and photoelectron spectroscopy experiments we demonstrate another unusual property of superhalogens. Unlike halogens, whose ability to accept an electron falls upon dimerization, B 2 O 4 , the dimer of BO 2 , has an electron affinity larger than that of the BO 2 building block. This ability of (BO 2 ) 2 and subsequent, higher oligomers (BO 2 ) n (n = 3 and 4), to retain their superhalogen characteristics can be traced to the enhanced bonding interactions between oxygen and boron atoms and due to the delocalization of the charge of the extra-electron over the terminal oxygen atoms. These results open the door to the design and synthesis of a new class of metal-free highly negative ions with potential for novel applications.Negative ions play an important role in chemistry not only because they are the building blocks of salts, but also because they are useful in purifying air, killing molds, and serving as anti-depressants. Halogens atoms readily form negative ions and have among the highest electron affinities of any element in the periodic table. However, as shown in Table 1, when halogen atoms combine to form molecules, their electron affinities are reduced, 1 i.e. halogens do not beget halogens. This decreasing trend is a consequence of the extra-electron occupying the antibonding orbital of X 2 (X = F, Cl, Br, and I) molecule. In this communication, we show that in contrast to halogens, dimerization of BO 2 , a well-known superhalogen, does not result in lowering of the EA. In addition, the higher oligomers, (BO 2 ) n (n = 3 and 4) also retain their superhalogen characteristics.More than half a century ago it was shown that PtF 6 could oxidize a Xe atom. 2 The electron affinity of this molecule was later estimated to be 6.76 eV, 3 much larger than the electron affinity of any halogen atom. Gutsev and Boldyrev 4 later termed such molecules as superhalogens and generalized the concept to include molecules with composition MX (m+1)/n , where m is the maximal valence of the metal atom M and n is the normal valence of the electronegative atom, X (n = 1 for halogen atoms). Subsequently, several experimental studies have confirmed the existence of superhalogens consisting of simple metal atoms, such as alkalis, Mg, and Al at the core and halogen atoms on the periphery. 5-7 Considerable research conducted in recent years has shown that superhalogens not only mimic the chemistry of halogens but also can be used to promote unusual reactions, 8 as a building block of energetic materials, 9 as dopants to increase the electrical conductivity of polymers, 10 for accessing high oxidation states of metal atoms, 11 as electrolytes in rechargeable batteries, 12 and in the production of organi...

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Experimental results of the search for inorganic fullerenes are presented. MonSm− and WnSm− clusters are generated with a pulsed arc cluster ion source equipped with an annealing stage. This is known to enhance fullerene formation in the case of carbon. Analogous to carbon, the mass spectra of the metal chalcogenide clusters produced in this way exhibit a bimodal structure. The species in the first maximum at low mass are known to be platelets. Here, the structure of the species in the second maximum is studied by anion photoelectron spectroscopy, scanning transmission electron microscopy, and scanning tunneling microcopy. All experimental results indicate a two-dimensional structure of these species and disagree with a three-dimensional fullerene-like geometry. A possible explanation for this preference of two-dimensional structures is the ability of a two-element material to saturate the dangling bonds at the edges of a platelet by excess atoms of one element. A platelet consisting of a single element only cannot do this. Accordingly, graphite and boron might be the only materials forming nano-spheres because they are the only single element materials assuming two-dimensional structures.