Dianionic tetraborates do exist as stable entities

Theoretical investigation of substituent effects on the relative stabilities and electronic structure of [BnXn]2- clusters

In this study, we provide a theoretical evaluation of relative stabilities and electronic structure for [B_nX_n]^2- clusters (n = 10, 12, 13, 14, 15, 16). Structural and electronic characteristics of [B_nX_n]^2- clusters are examined by comparison with the [B₁₂X₁₂]^2- counterparts with a focus on the substituent effects (X = H, F, Cl, Br, CN, BO, OH, NH₂) on the electronic structure, electron detachment energies, formation enthalpies, and charge distributions. For the electronic structure and electron detachment energies, substituent effects on boron clusters are shown to follow a very similar trend to the mesomeric and inductive effects (± M and ± I) of π-conjugated systems, and the most stable derivatives in terms of HOMO/LUMO and electron detachment energies are calculated for CN and BO substituents due to strong -M effects. In the case of formation enthalpies for larger boron clusters (n ≥ 13), the icosahedral barrier is shown to increase with the halogen and CN substitution, whereas it is possible to reduce the icosahedral barrier for the cases of X = OH and NH₂. It is shown that this reduction results from destabilizing the [B₁₂X₁₂]^2- cluster with electronic (+ M) and symmetry effects induced by OH and NH₂ ligands.

Properties of perhalogenated {closo-B10} and {closo-B11} multiply charged anions and a critical comparison with {closo-B12} in the gas and the condensed phase

Dependence of electronic properties and reactivity of closo-borates with size and halogen substituent was investigated.

Improvement in hydrogen binding ability of closo-dicarboranes via functionalization and designing of extended frameworks

Neutral closo-dicarboboranes are reported to have very low H₂ binding ability. Herein, we report an improvement in H₂ binding energy (E_b) of C₂B₄H₆ by substituting H atoms with different functional groups like X = F, Cl, Br, and XY = BO, CN and NC via quantum-chemical density functional theory based computations. In going from B₆H₆^2- to C₂B₄H₆, the E_b value is reduced from 14.6 kJ mol^-1 to 2.7 kJ mol^-1. C₂B₄X₆ and C₂B₄(XY)₆ systems, which can bind a total of eight H₂ molecules, with one H₂ molecule occupying at each B-B-C face, possess an E_b value per H₂ in the range of 4.5 kJ mol^-1 for X = F, 3.9 kJ mol^-1 for X = Cl, 5.9 kJ mol^-1 for X = Br, 6.8 kJ mol^-1 for XY = BO, 5.8 kJ mol^-1 for XY = CN and 5.2 kJ mol^-1 for XY = NC. The improvement in E_b value is found to be the highest in case of C₂B₄(BO)₆, which has the ability to bind 6.6 gravimetric wt% of H₂. The situation can be made more favorable by applying an external electric field. Energy decomposition analysis reveals that although the dispersion interaction (ca. 55-65%) has significant role in binding H₂ with such types of molecules, contribution from electrostatic and orbital interaction is also considerable. Further, we modeled an extended system by linking C₂B₄(BO)_n through 'C ≡ C' units for H₂ storage purpose. The energy difference between the highest occupied and the lowest unoccupied molecular orbitals gradually lessens with the increase in molecular length. Therefore, it can be tuned gradually by controlling the chain length, which may further open up their potency in the field of electronics. Graphical abstract C₂B₄X₆ (X = F, Cl, Br) and C₂B₄(XY)₆ (XY = BO, CN, NC) show enhanced H₂ binding ability from C₂B₄H₆. Further, 1D, 2D and 3-D frameworks can be built by joining C₂B₄(BO)_n units via 'C ≡ C' linkage.

Rational Design of Stable Dianions by Functionalizing Polycyclic Aromatic Hydrocarbons

Using density functional theory, we have carried out a systematic study of the stability and electronic properties of neutral and multiply charged molecules B_n C_10-n X₈ (n=0, 1, 2; X=H, F, CN). Our main objective is to explore if the replacements of core C atoms and/or H atoms in naphthalene (C₁₀ H₈ ) can enhance the stability of their dianions. Indeed, we find that the dianions of B_n C_10-n (CN)₈ are more stable than their monoanions with energies of 0.61 eV, 0.57 eV, and 1.97 eV for n=0, 1, 2, respectively. In addition, polycyclic aromatic hydrocarbons become stable as dianions only when H atoms are substituted by more electronegative species. Thus, a rational design approach by tailoring composition and ligands can lead to a new class of organic molecules that are capable of carrying multiple charges.

Deciphering chemical bonding in BnHn2−(n = 2–17): flexible multicenter bonding

Deciphering flexible multicenter bonding incloso-borane dianions B_nH_n²⁻.

Role of ligands in the stability of BnXn and CBn−1Xn (n = 5–10; X = H, F, CN) and their potential as building blocks of electrolytes in lithium ion batteries

We predict a series of boron-cage-based stable (di-)anions, and demonstrate them to be high-performance electrolytes in Li-ion batteries.

STRUCTURE AND STABILITY OF MONOCYCLIC $({\rm CH})_{4-n} ({\rm BL})_{n}^{2-}$(L = CO, N2, CS) DIANIONS AND THEIR DILITHIUM COMPLEXES

Structure and stability of monocyclic [Formula: see text] dianions ( L = CO , N 2, CS ) with 6π-electrons, which are isolobal with cyclobutadiene dianion [Formula: see text], have been investigated at the B3LYP and CCSD(T) levels of theory. ( CH )3( BL )2- have non-planar singlet ground states. [Formula: see text] have planar singlet ground states, while [Formula: see text] isomers have folded four-membered central rings. Both [Formula: see text] and [Formula: see text] have planar ground states, the ground state of [Formula: see text] has a six-membered ring with two bridging and one terminal CS. Both [Formula: see text] and [Formula: see text] have reduced aromaticity compared to [Formula: see text] as indicated by the less negative nucleus independent chemical shifts (NICS) values. The mono-, di- and trisubstituted ( CH )3( BL )2-, [Formula: see text], and [Formula: see text] also have reduced aromaticity, while the 1,3-substituted [Formula: see text] have positive NICS values due to the localization of the negative charge at the ring carbon centers. In addition, the electrostatic stabilization of Li + in favor of the singlet or triplet states depends on the nature of their structures.

In situ surface-enhanced Raman scattering spectroelectrochemistry of oxygen species

In situ surface-enhanced Raman scattering (SERS) combined with electrochemical analysis is applied to the determination of oxygen species on silver electrodes in alkaline hydroxide aqueous solution at room temperature and gold electrodes in carbonate melts at high temperature. This technique, referred to as SERS spectroelectrochemistry, reveals Raman spectral lines in the 500-1100 cm(-1) range under electrode potential scanning, assignable to superoxide ions (O2-) and peroxide ions (O2(2-)) on the electrode surface. These lines for oxygen molecule species have potential dependence with changing potential. In the alkaline hydroxide aqueous solution, the Raman peaks due to oxygen molecules are observed at potentials between 0.2 V and -0.8 V (vs. Ag/AgCl) only in the cathodic scan. This irreversible behavior in cyclic voltammograms indicates the existence of an intermediate stage in the oxygen reduction process, in which oxygen is released from the AgO films on the electrode at potentials corresponding to the onset of the last current peak in the voltammogram. This liberated oxygen molecule remains in solution at the interface until hydroxyls or water molecules are formed when the potential reaches the potential zero charge (PZC). In the high-temperature carbonate melts, Raman lines at 1047, 1080, and 800 cm(-1) are apparent for the eutectic (62 + 38) mol% (Li + K)CO3 melt at 923 K, and at 735 cm(-1) for the Li2CO3 melt at 1123 K. These results suggest that oxygen reduction in the Li2CO3 melt involves only peroxide ions, while that in (62 + 38) mol% (Li + K)CO3 involves both peroxide and superoxide ions at the three-phase boundary interface.

Photoelectron spectroscopy of fullerene dianions C762−, C782−, and C842−

We report laser photoelectron spectra of the doubly negatively charged fullerenes C(76) (2-), C(78) (2-), and C(84) (2-) at 2.33, 3.49, and 4.66 eV photon energy. From these spectra, second electron affinities and vertical detachment energies, as well as estimates for the repulsive Coulomb barriers are obtained. These results are discussed in the context of electrostatic models. They reveal that fullerenes are similar to conducting spheres, with electronic properties scaling with their size. The experimental spectra are compared with the accessible excited states of the respective singly charged product ions calculated in the framework of time dependent density functional theory.