16 research outputs found
UNCONVENTIONAL SUPERHALOGENS: DESIGN AND APPLICATIONS
Electron affinity is one of the most important parameters that guide chemical reactivity. Halogens have the highest electron affinities among all elements. A class of molecules called superhalogens has electron affinities even greater than that of Cl, the element with the largest electron affinity (3.62 eV). Traditionally, these are metal-halogen complexes which need one electron to close their electronic shell. Superhalogens have been known to chemistry for the past 30 years and all superhalogens investigated in this period are either based on the 8-electron rule or the 18-electron rule. In this work, we have studied two classes of unconventional superhalogens: borane-based superhalogens designed using the Wade-Mingo’s rule that describes the stability of closo-boranes, and pseudohalogen based superhalogens. In addition, we have shown that superhalogens can be utilized to build hyperhalogens, which have electron affinities exceeding that of the constituent superhalogens, and also to stabilize unusually high oxidation states of metals
Potential of ZrO clusters as replacement Pd catalyst
Atomic clusters with specific size and composition and mimicking the chemistry of elements in the periodic table are commonly known as superatoms. It has been suggested that superatoms could be used to replace elements that are either scarce or expensive. Based on a photoelectron spectroscopy experiment of negatively charged ions, Castleman and co-workers [Proc. Natl. Acad. Sci. U.S.A.107, 975 (2010)] have recently shown that atoms of Ni, Pd, and Pt which are well known for their catalytic properties, have the same electronic structure as their counterpart isovalent diatomic species, TiO, ZrO, and WC, respectively. Based on this similarity they have suggested that ZrO, for example, could be a replacement catalyst for Pd. Since catalysts are seldom single isolated atoms, one has to demonstrate that clusters of ZrO also have the same electronic structure as same sized Pd clusters. To examine if this is indeed the case, we have calculated the geometries, electronic structure, electron affinity, ionization potential, and hardness of Pd n and (ZrO) n clusters (n = 1-5). We further studied the reaction of these clusters in neutral and charged forms with H2, O2, and CO and found it to be qualitatively different in most cases. These results obtained using density functional theory with hybrid B3LYP functional do not support the view that ZrO clusters can replace Pd as a catalyst
Prediction of Superhalogen-Stabilized Noble Gas Compounds
The discovery of HArF has generated
renewed interest in the chemistry
of noble gases, particularly their hydrides. Though many weak complexes
of noble gases bound by van der Waals interactions are known, the
number of halogenated noble gas compounds, HNgX (Ng = noble gas; X
= halogen), where the noble gas atom is chemically bound, is limited.
These molecules are metastable, and their specialty is that there
is substantial ionic bonding between the noble gas atom and the halogen
atom. In this Letter, it is shown using density functional theory
and second-order Møller–Plesset perturbation theory that
by replacing the halogen atoms by superhalogens (Y), whose electron
affinities are much larger than those of halogens, more ionic bonds
between Ng and Y can be attained. Moreover, the superhalogen-containing
noble gas hydrides, HNgY, are more stable compared to their halogenated
counterparts
Zn in the +III Oxidation State
The possibility that the group 12 elements Zn, Cd, and
Hg can exist
in an oxidation state of +III or higher has fascinated chemists for
decades. It took nearly 20 years before experiments could confirm
the theoretical prediction that Hg indeed can exist in the +IV oxidation
state. While this unusual property of Hg is attributed to relativistic
effects, Zn, which is much less massive than Hg, has not been expected
to have an oxidation state higher than +II. Using density functional
theory, we have shown that an oxidation state of +III for Zn can be
realized by choosing specific ligands with large electron affinities.
We demonstrate this by a systematic study of the interaction of Zn
with the ligands F, BO<sub>2</sub>, and AuF<sub>6</sub>, whose electron
affinities are progressively higher (3.4, 4.5, and 8.4 eV, respectively).
The discovery of higher oxidation states of elements can help in the
formulation of new reactions and hence in the development of new chemistry
Spontaneous formation of gold nanostructures in aqueous microdroplets
Reactions in aqueous microdroplets can significantly differ from those in bulk. Here, the authors report microdroplets that not only accelerate gold nanoparticle formation by several orders of magnitude but also promote spontaneous nanostructure formation with no reducing agents or template