ThH5: An Actinide-Containing Superhalogen Molecule

Thorium and its compounds have been widely investigated as important nuclear materials. Previous research focused on the potential use of thorium hydrides, such as ThH₂, ThH₄, and Th₄H₁₅, as nuclear fuels. Here, we report studies of the anion, ThH₅⁻, by anion photoelectron spectroscopy and computations. The resulting experimental and theoretical vertical detachment energies (VDE) for ThH₅⁻ are 4.09 eV and 4.11 eV, respectively. These values and the agreement between theory and experiment facilitated the characterization of the structure of the ThH₅⁻ anion and showed its neutral counterpart, ThH₅ to be a superhalogen. ThH₅⁻, which exhibits a C_4v structure with five Th−H single bonds, possesses the largest known H/M ratio among the actinide elements, M. The adaptive natural density partitioning (AdNDP) method was used to further analyze the chemical bonding of ThH₅⁻ and to confirm the existence of five Th−H single bonds in the ThH₅⁻ molecular anion.     

Quantum chemical study of IrFn (n = 1–7) clusters: An investigation of superhalogen properties

In present investigation, the interactions of iridium (Ir) atom with fluorine (F) atoms have been studied using the density functional theory. Up to seven F atoms were able to bind to a single Ir atom which resulted in increase of electron affinities successively, reaching a peak value of 7.85 eV for IrF₇. The stability and reactivity of these clusters were analyzed by calculating highest occupied molecular orbital (HOMO)–LUMO gaps, molecular orbitals and binding energies of these clusters. The unusual properties of these clusters are due to the involvement of inner shell 5d‐electrons, which not only allows IrF_n clusters to belong to the class of superhalogens but also shows that its valence can exceed the nominal value of 2. © 2012 Wiley Periodicals, Inc.     

Theoretical investigations on the superhalogen properties and interaction of PdOn (n = 1–5) species

Density functional calculations on the ground state geometries and stabilities of PdO_n species (n = 1–5) are performed in neutral as well as anionic forms. Calculations reveal that Pd can bind stably with four O atoms indicating the maximum oxidation state of Pd as high as +8. The electron affinities of PdO_n suggest that these species behave as superhalogens for n ≥ 2. The large electron affinities of PdO_n species along with stability of their anions point toward the synthesis of new class of compounds having unusual oxidizing capabilities. This possibility is explored by considering the interaction of PdO₂ superhalogen with Ca atom which forms a stable CaPdO₂ complex. In this complex, PdO₂ unit closely mimics the behavior of O atom when compared with CaO molecule. © 2013 Wiley Periodicals, Inc.     

Electron affinity of modified benzene

The electron affinities of organic molecules obeying Hückel's rule of aromaticity are vanishingly small, if not negative. For example, benzene, a classic example of an aromatic molecule, has an electron affinity of −1.15 eV. Using density functional theory, we have systematically calculated the electron affinities and vertical detachment energies of C₆H₆ by substituting H with halogen (F) and superhalogen (BO₂) moieties, as well as replacing one of the C atoms with B. The ground state geometries were obtained by examining about 330 isomers. The electron affinities are found to steadily increase with these substitutions/replacements, even surpassing that of Cl, the element with the highest electron affinity in the periodic table, in the case of C₅BH(BO₂)₅. In some special cases such as C₆H₅(BO₂) the electron affinity and vertical detachment energy differ by as much as 5 eV, indicating substantial changes in the geometry as the electron is removed from the anion. We hope that the ability to change the negative electron affinity of C₆H₆ to large positive values by substituting H and/or replacing C atom will motivate experimental studies.     

Fullerene “Superhalogen” Radicals: the Substituent Effect on Electronic Properties of 1,7,11,24,27‐C60X5

Hexasubstituted fullerenes with the skew pentagonal pyramid (SPP) addition pattern are predominantly formed in many types of reactions and represent important and versatile building blocks for supramolecular chemistry, biomedical and optoelectronic applications. Regioselective synthesis and characterization of the new SPP derivative, C₆₀(CF₃)₄(CN)H, in this work led to the experimental identification of the new family of “superhalogen fullerene radicals”, species with the gas‐phase electron affinity higher than that of the most electronegative halogens, F and Cl. Low‐temperature photoelectron spectroscopy and DFT studies of different C₆₀X₅ radicals reveal a profound effect of X groups on their electron affinities (EA), which vary from 2.76 eV (X=CH₃) to 4.47 eV (X=CN). The measured gas‐phase EA of the newly synthesized C₆₀(CF₃)₄CN equals 4.28 (1) eV, which is about 1 eV higher than the EA of Cl atom. An observed remarkable stability of C₆₀(CF₃)₄CN^? in solution under ambient conditions opens new venues for design of air‐stable molecular complexes and salts for supramolecular structures of electroactive functional materials.     

Prospective of the LDI MS to characterization the corrosion products of silver-copper alloys on an example of the Ag-Cu-X (X- Zn,Pd, In) system

This work presents the perspective of applying the laser desorption/ionization mass spectrometry (LDI MS) for characterization the anode film of the Ag₆₀Cu₂₆Zn₁₄, Ag_58.5Cu_31.5Pd₁₀, and Ag₆₃Cu₂₇In₁₀ alloys (at high concentrations of chloride ions in solutions). The reference LDI mass spectra of anode films of pure Ag and Cu have been used for the identification of product corrosion. Knowing the clusters detected in the reference spectra lead to the facilitating identification of the LDI mass spectrum of the sample and reduces the analysis time. The LDI MS analysis of these alloys revealed that the predominant corrosion product are AgCl (from Ag_nCl_n+1^?/+, n = 1–3), and CuCl (from “superhalogen” Cu_mCl_n^? clusters, m = 1–2, n = 2–6); it also revealed Cu₂(OH)₃Cl (from Cu₂(OH)(H₂O)₂⁺) and Cu₂O (from Cu(H₂O)⁺, Cu₂O doped with chlorine). These results are in accordance with the X-ray diffraction and Raman analysis. The LDI MS spectra of alloys contain the additional peaks formed due to the mutual influences of different metals in the alloys (AgCuCl₃^? (AgCl-CuCl₂^?), AgCu₂Cl₄^? (AgCl-CuCl-CuCl₂^?), and Ag₂CuCl₄^? (AgCl-AgCl-CuCl^?), which is consistent with the identified corrosion products. It should be noted that the LDI MS suggest the presence of CuCl₂, which can be interpreted as the corrosion products retained in the porous films of alloys, and not detected by the other methods due to a small amount. The future theoretical and experimental studies of metal clusters, significant for metallurgy, can contribute that the LDI MS is becoming a powerful analytical tool for characterization the metal surfaces.     

Fluorinated ferromagnetic metal clusters and their superhalogen behaviour

Density functional theory calculations on the ground-state geometries and spin multiplicities of neutral and anionic ferromagnetic metal fluoride clusters, MF_n (M = Fe, Co and Ni; n = 1–7), have been performed. The results show that in the case of FeF_n and CoF_n clusters, a maximum of five F atoms can be bound atomically to metal atoms while four in the case of NiF_n. The remaining F atoms bind either very weakly or molecularly. The stabilities of all MF_n clusters are discussed by calculating dissociation energies to F atoms and F₂ molecules. We notice that the anionic species are relatively more stable than corresponding neutrals. The electron affinities of these clusters are very large, reaching values as high as 7.98 eV. Therefore, these clusters can be regarded as superhalogens.     

Structural properties and nonlinear optical responses of superatom compounds BF4‐M (M = Li,FLi2, OLi3, NLi4)

A new type of superhalogen‐(super)alkali compound, BF₄‐M (M = Li, FLi₂, OLi₃, NLi₄), is theoretically characterized at the MP2/6‐311+G(3df) level. The interaction between superhalogen BF₄ and different shaped (super)alkali M is found to be strong and ionic in nature. Bond energies of these BF₄‐M species are in the range of 200.0–226.7 kcal/mol at the CCSD(T)/6‐311+G(3df) level, which are much larger than the traditional ionic bond energy of 130.1 kcal/mol of FLi. In addition, different from the alkali halides, the BF₄‐M compounds prefer to dissociate into ions rather than neutral fragments. The energetic properties of BF₄‐M are found to be closely related to the size of the M subunit. The different effects of superalkali and superhalogen subunits on the nonlinear optical (NLO) properties of such superatom compounds are also revealed. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Ab initio investigations on lithium–superhalogen (Li–X) complexes (X = LiF2, BeF3, BF4 and PF6): competition between s-block and p-block anions

In this work, we investigate the formation of Li–X complexes by interaction of Li cation and superhalogen (X) anions belonging to s block (X = LiF₂, BeF₃) and p block (X = BF₄, PF₆). We discuss their structures and stabilities using the quantum chemical method at MP2/aug-cc-pVDZ level of theory. Considering polarisable continuum model, solvent effects are taken into account in a polar organic solvent, namely diethyl ether. Our findings establish that electronic and chemical properties of Li–LiF₂ and Li–BeF₃ closely resemble Li–BF₄ and Li–PF₆. However, Li–LiF₂ may dissociate preferably into LiF salt; Li–BeF₃ appears as a close analogue of Li–BF₄, which is significantly stabilised by the solvent. Thus, the superhalogen anions possess electronic integrity irrespective of the nature of central atom.