Vertical Electron Detachment Energies Research Articles

Carborane superhalide bases and their conjugate Brønsted-Lowry Superacids: Electron binding energies and Dyson orbitals

Superacidity in protonated carboranes arises from properties of conjugate anions: shallow, uniform electrostatic potentials, large electron detachment energies and nodal structure in Dyson orbitals. Vertical electron detachment energies (VEDEs) and Dyson orbitals of closo CHB11X11− (X = H, F, Cl) carboranes calculated with ab initio electron-propagator theory in the renormalized partial third order (P3+) and non-diagonal, renormalized, second-order (NR2) approximations are in close agreement with anion photoelectron spectra. Whereas first VEDEs to 2E2 final states of all three of these superhalide anions exceed 6 eV, a more promising strategy for enhancing superacidity is increasing the anionic base’s second VEDE to the lowest 2E1 final state.

Combining proton and silaborane-based superhalogen anions - an effective route to new superacids as verified via systematic DFT calculations.

Based on systematic DFT calculations, silaborane-based superhalogen anions, which obey the Wade-Mingos rule, are shown to be capable of giving rise to superacids via their combination with protons. Compared to previous carborane-based systems, the acidities of the composites here are stronger in both the gas phase and solution phase. Thus, the potential of candidates based on silaborane could be greater than those based on carborane in the search for ultra-strong acidic systems. Within a given group, a higher superhalogen anion vertical electron detachment energy (VDE) generally leads to stronger acidity. This consistency arises from the dominant role of the VDE, as established through the decomposition of the gas-phase acidity into different contributions. Thus, constructing superacids from superhalogens is a rational route whose future should be positive. Besides the VDE, other effects, i.e., the deformation energy (DE) and bond dissociation energy (BDE), could also be crucial, especially in terms of the differences between the acidities of composites belonging to different groups. A comparison between the results in the gas phase and solution phase indicates that complete calculations of both gas-phase ΔGacid and solution-phase pKa values are necessary to obtain an unbiased description of the acidity. The solvation free energies of the participants in the deprotonation process, especially the conjugate acid, are responsible for the discrepancies between gas phase and solution phase behavior.

Formation of Enormously Strongly Bound Anionic Clusters Predicted in Binary Superacids.

The possible formation of the (AlF4(HF) n)- ( n = 1-8 and 12), (AsF6(HF) n)-, and (SbF6(HF) n)- ( n = 1-6 and 12) anionic clusters of a superhalogen nature is predicted in the solutions of binary HF/AlF3, HF/AsF5, and HF/SbF5 Lewis-Brønsted superacids on the basis of ab initio calculations. Our results show that all systems investigated represent extremely strongly bound anions characterized by vertical electron detachment energies (VDEs) that significantly exceed 10 eV. The VDE values estimated for the (AlF4(HF)12)-, (AsF6(HF)12)-, and (SbF6(HF)12)- systems are predicted to be 13.96, 14.03, and 14.03 eV, respectively, and are the largest vertical electron detachment energies reported in the literature thus far.

Electron Propagator Methods for Vertical Electron Detachment Energies of Anions: Benchmarks and Case Studies.

Ab initio electron propagator methods are efficient and accurate means of calculating vertical electron detachment energies of closed-shell, molecular anions with nuclei from the first three periods. Basis set extrapolations enable definitive comparisons between electron propagator results and benchmarks defined by total energy differences obtained with coupled-cluster, single, double, plus perturbative triple substitution theory. The best compromises of accuracy and efficiency are provided by the renormalized, partial third-order, diagonal (P3+) self-energy and by the nondiagonal, renormalized, second-order (NR2) approximation. The outer-valence Green function, the two-particle-one-hole Tamm-Dancoff approximation, the third-order algebraic diagrammatic construction, and the renormalized third-order methods also are examined. A detailed analysis of errors for small anions is performed. Case studies include F-(H2O) and Cl-(H2O) complexes, C5H5-, two P2N3- pentagonal rings, and a superhalide, Al(BO2)4-, whose electron detachment energy is more than double those of the halide anions. These applications illustrate the versatility of electron propagator methods, their utility for interpreting negative-ion photoelectron spectra, and their promise in the discovery of unusual properties and patterns of chemical bonding. Composite methods, which combine basis set effects calculated at the relatively efficient diagonal, second-order level and higher correlation effects calculated with small basis sets, provide excellent estimates of basis set-extrapolated P3+ or NR2 results and facilitate applications to large molecules. In the P3+ and NR2 methods, a judicious choice of low-order couplings between hole operators that correspond to the assumptions of Koopmans's theorem and operators that describe final-state relaxation and polarization and initial-state correlation leads to predictive accuracy, computational efficiency, and interpretive lucidity.

Why do higher VDEs of superhalogen not ensure improved stabilities of the noble gas hydrides promoted by them? A high-level ab initio case study.

A series of 20 composite structures, consisting of superhalogen and noble gas (Ng) hydrides, was explored via high-level coupled-cluster single, double and perturbative triple excitations calculations in this work. The existence of these composites, as local minima on the potential energy surface, arises from the charge transfer from the Ng hydride part to the superhalogen moiety. Clearly, this transfer could lead to stabilizing the interaction of the ionic type between the two components. The driving force of the charge transfer should be the high vertical electron detachment energy (VDE) of the superhalogen part leading to its enough capability of extracting the electron from the Ng hydride moiety. However, except triggering the ionic attractive interaction, there is nomonotonic correlation between the VDE value and the thermodynamic stability of the whole composite. This counter-intuitive result actually originates from the fact that, irrespective of various superhalogens, only two of their F ligands interact with the Ng atoms directly. Thus, although leading to higher VDE values, the increase in the number of electronegative ligands of the superhalogen moiety does not affect the stabilizing interaction of the composites here directly. In other words, with the necessary charge transfer generated, further increase of the VDE does not ensure the improvement of the thermodynamic stabilities of the whole composite. Moreover, in the transition state of the exothermic dissociation channel, more F atoms will give rise to higher probability of additional attractions between the F and H atoms which should lower the energy barrier. That is to say, increasing VDE, i.e., having more F atoms in many cases, will probably reduce the kinetic stability. Knowing the inevitable existence of the exothermic channel, kinetic stability is crucial to the ultimate goal of experimental observation of these Ng hydrides. Thus, in some cases, only the superhalogen itself may not provide enough information for the correct prediction on the properties of the whole composites. The understanding of the superhalogen-based composites will provide valuable information on the functional properties as well as the application potential of superhalogen clusters. Thus, the corresponding researches should focus on not only the superhalogen itself but also other related aspects, especially the details of the interaction between different parts.

Structural and Electronic Properties in Titanium-Doped Stannum Clusters: Comparison with Their Anions and Cations

The neutral, anionic, and cationic SnnTi(0, ±1) (n = 1–10) units are researched computationally using a density functional theory. The optimized geometries of SnnTi(0, ±1) clusters illustrate that the most stable structures between the neutral, anionic, and cationic clusters keep the similar structures when n = 1, 2, 4, 5, 9,10, however, we find that the obtained most stable clusters of the size n = 3, 6, 7, 8 are different. From the optimized results a systematic analysis is carried out to obtain the relative stabilities, electronic properties, and natural population analysis of SnnTi(0, ±1) clusters. The relative stabilities are investigated by analyzing the binding energies, fragmentation energies, and the second order energies difference of SnnTi(0, ±1) clusters, the results show that the binding energies of anionic clusters are obviously larger than those of neutral and cationic clusters. The HOMO–LUMO gap, the adiabatic electron affinity, vertical electron detachment energy, adiabatic ionization potential energy, and vertical ionization potential energy respond the electronic property, we obtain that the Ti atom changes the electron structures of stannum clusters. To discuss reliable charge transfer information from SnnTi clusters to SnnTi− clusters and SnnTi+ clusters, the natural population analysis of neutral, anionic, and cationic SnnTi(0,±1) clusters are calculated.

Toward the detection of the triatomic negative ion SPN-: Spectroscopy and potential energy surfaces.

High level theoretical calculations using coupled-cluster theory were performed to provide an accurate description of the electronic structure, spectroscopic properties, and stability of the triatomic negative ion comprising S, N, and P. The adiabatic electron affinities (AEAs) and vertical detachment energies (VDEs) of PNS, SPN, PSN, and cyc-PSN were calculated. The predicted AEA and VDE of the linear SPN isomer are large: 2.24 and 3.04 eV, respectively. The potential energy surfaces (PESs) of the lowest-lying electronic states of the SPN- isomer along the PN and SP bond lengths and bond angle were mapped. A set of spectroscopic parameters for SPN-, PNS-, and PSN- in their electronic ground states is obtained from the 3D PESs to help detect these species in the gas phase. The electronic excited state SPN-(12A″) is predicted to be stable with a long lifetime calculated to be 189.7 μs. The formation of SPN- in its electronic ground state through the bimolecular collision between S- + PN and N + PS- is also discussed.

Stability of the [formula omitted] and [formula omitted] superhalogen anions and the acidity of the HTinF4n+1 and HGenF4n+1 (n = 1–3) superacids

Polynuclear superhalogen anions containing titanium and germanium as the central atoms and fluorine atoms as the ligands were investigated on the basis of ab initio calculations employing the CCSD(T), MP2 and OVGF methods and the 6-311++G(d,p) basis set. The structures of most stable isomers of TinF4n+1− and GenF4n+1− (n = 1–3) anions, their thermodynamic stability and the vertical electron detachment energies are provided and discussed. The possible existence and stability of the corresponding HTinF4n+1 and HGenF4n+1 neutral molecules, obtained by the protonation of the TinF4n+1− and GenF4n+1− anions, are also considered. The most important findings include the prediction of large electronic stability of the TinF4n+1− and GenF4n+1− anions (exceeding 9.7 eV in all cases and approaching 12 eV for n = 3) and significant acidity of the HTinF4n+1 and HGenF4n+1 compounds (manifested by their Gibbs free deprotonation energies in the 258.7–302.6 kcal/mol range).

Superhalogen-based composite with strong acidity-a crossing point between two topics

Correlation between the acidity and the vertical electron detachment energy verifies the rationality of constructing superacid from superhalogen.

Comparisons of the Functional and Basis Set Combinations for Silicon Oxide Clusters: A Density Functional Theory Study

In this study, we evaluate three functionals (B3LYP, PBE, and M06) and 29 basis sets to find a suitable model to calculate silicon oxide clusters using density functional theory. The experimental values of electron affinities and vertical detachment energies of SiO2 and Si2O4 clusters were compared with the calculated ones using combinations of the three functionals and 29 basis sets. The calculated SiO bond lengths and SiOSi angles of Si2O7 cluster were also compared with the experimental values. Our conclusion is that the PBE/DGDZVP model is the best for calculating the structural and electronic properties of silicon oxide clusters.

Electron affinity of modified benzene

AbstractThe 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.

Toward the preparation of the HAuF6, HAu2F11, and HAu3F16 superacids: Theoretical study

AbstractWe apply the B3LYP and QCISD theoretical methods with the 6‐311++G(d,p) basis set and the LANL2DZ effective core potentials to investigate the reaction paths leading to the preparation of the HAuF6, HAu2F11, and HAu3F16 superacids. The Gibbs free energies of deprotonation of these systems are calculated to estimate their acid strength. The thermodynamic stability of the corresponding anionic precursors ((AuF6)–, (Au2F11)–, and (Au3F16)–) and their vertical excess electron detachment energies are evaluated and discussed. The suggested route of the HAu2F11 preparation involves the F– attachment to the Au2F10 reactant which results in the formation of the (Au2F11)– anion whose protonation yields the HAu2F11 superacid. The suggested HAuF6 superacid preparation route is based on a qualitatively similar scheme and involves the conversion of the AuF5 reactant into the (AuF6)– anion followed by its protonation. The proposed path for the HAu3F16 superacid preparation involves the attachment of AuF5 to HAu2F11.

E3 M3+ (E=C-Pb, M=Li-Cs) Clusters: The Smallest Molecular Stars.

Extensive potential energy surface explorations of twenty-five clusters with the formula E3 M3+ (E=Group 14 element and M=Group 1 element) through density functional theory and high-level ab initio computations reveal that the lowest-energy isomer for all these systems corresponds to a non-classical D3h star-like structure in the singlet state, where three M atoms interact electrostatically with the triangular E3 core, occupying three bridging positions around it. More than 18 200 calculations were done in the search for the minima structures, starting with a first phase at the PBE0/LANL2DZ level and ending with an analysis of the most representative clusters at the CCSD(T)/def2-TZVP//PBE0/def2-TZVP level. The title clusters represent the smallest molecular stars with three planar tetracoordinate E atoms (E=Group 14 element). All these E3 M3+ clusters behave like superalkali cations with small vertical electron affinities (smaller than Cs), large vertical electron detachment energies, and HOMO-LUMO energy gaps. Their energetics, bonding, and electron delocalization are discussed in detail. The high stability of these clusters is reflected from the large dissociation energy needed for different dissociation channels. The electron delocalization is confirmed by the presence of two delocalized π electrons over the E3 core and strong diatropic responses.

Geometries, stabilities, and electronic properties analysis in InnNi(0,±1) clusters: Molecular modeling and DFT calculations**Project supported by the Cultivating Program of Excellent Innovation Team of Chengdu University of Technology (Grant No. KYTD201704), the Cultivating Program of Middle-aged Backbone Teachers of Chengdu University of Technology (Grant No. 10912-KYGG201512), the National Natural Science Foundation of China (Grant No. 11404042), the Science Fund from

Density functional theory (DFT) with the B3LYP method and the SDD basis set is selected to investigate InNi, InNi, and InNi (–14) clusters. For neutral and charged systems, several isomers and different multiplicities are studied with the aim to confirm the most stable structures. The structural evolution of neutral, cationic, and anionic InNi clusters, which favors the three-dimensional structures for n = 3 – 14. The main configurations of the InNi isomers are not affected by adding or removing an electron, the order of their stabilities is also nearly not affected. The obtained binding energy exhibits that the Ni-doped In cluster is the most stable species of all different sized clusters. The calculated fragmentation energy and the second-order energy difference as a function of the cluster size exhibit a pronounced even–odd alternation phenomenon. The electronic properties including energy gap , adiabatic electron affinity (AEA), vertical electron detachment energy (VDE), adiabatic ionization potential energy (AIP), and vertical ionization potential energy (VIP) are studied. The total magnetic moments show that the different magnetic moments depend on the number of the In atoms for charged InNi. Additionally, the natural population analysis of InNi clusters is also discussed.

Superhalogen properties of hetero-binuclear anions MM′F4− and MM″F5− (M = Li, Na, M′ = Be, Mg, Ca; M″ = B, Al, Ga)

Hetero-binuclear superhalogen anions, namely MM′F4− and MM″F5− (M=Li, Na; M′=Be, Mg, Ca; M″=B, Al, Ga), have been theoretically characterized at the MP2(FULL)/6-311+G(3df) level. It is found that two central atoms can be linked by at most three fluorine ligands. The large vertical electron detachment energies (VDEs, 7.449–8.978eV) verify the superhalogen identity of these anions. The VDEs of both MM′F4− and MM″F5− decrease when the atomic size of M increases whereas increase with the size of M′ and M″. Besides, the extra electron distribution also has effect on the VDEs of such superhalogen anions.

Dinuclear superhalogen anions containing two different central atoms

Novel dinuclear superhalogen anions containing two different central atoms (i.e., LiNaF3−, BeMgF5−, and AlBF7–) were investigated theoretically on the basis of ab initio MP2 and CCSD(T) calculations. Their vertical electron detachment energies, thermodynamic stability and the nature of doubly occupied highest molecular orbitals were examined and discussed. All the anions studied in this work were found stable against fragmentation processes and are characterized by significant VDE values (8.12–10.96eV at the OVGF/6-311+G(3df) level) comparable to those of their corresponding classical counterparts.

Transitions from Stable to Metastable States in the Cr2On and Cr2On- Series, n = 1-14.

The geometrical and electronic structures of the Cr2On and Cr2On- clusters are computed using density functional theory with a generalized gradient approximation in the range of 1 ≤ n ≤ 14. Local total spin magnetic moments, polarizabilities, binding energies per atom, and energies of abstraction of O and O2 are computed for both series along with electron affinities of the neutrals and vertical detachment energies of the anions. In the lowest total energies states of Cr2O2, Cr2O3, Cr2O4, Cr2O14, Cr2O3-, Cr2O4-, and Cr2O14-, total spin magnetic moments of the Cr atoms are quite large and antiferromagnetically coupled. In the rest of the series, at least one of the Cr atoms has no spin-magnetic moment at all. The computed vertical electron-detachment energies of the Cr2On- are in good agreement with experimental values obtained in the 1 ≤ n ≤ 7 range. All neutral Cr2On possess electron affinities larger than the electron affinities of halogen atoms when n > 6 and are thus superhalogens. It is found that the neutrals and anions are stable with respect to the abstraction of an O atom in the whole range of n considered, whereas both neutrals and anions became unstable toward the loss of O2 for n > 7. The polarizability per atom decreases sharply when n moves from one to four and then remains nearly constant for larger n values in both series. The largest members in both series, Cr2O14 and Cr2O14-, possess the geometrical structures of the Cr2(O2)7 type by analogy with monochromium Cr(O2)4.

Electrophilicity of oxalic acid monomer is enhanced in the dimer by intermolecular proton transfer.

We have analyzed the effect of excess electron attachment on the network of hydrogen bonds in the oxalic acid dimer (OA)2. The most stable anionic structures may be viewed as complexes of a neutral hydrogenated moiety HOA˙ coordinated to an anionic deprotonated moiety (OA-H)-. HOA˙ acts as a double proton donor and (OA-H)- as a double proton acceptor. Thus the excess electron attachment drives intermolecular proton transfer. We have identified several cyclic hydrogen bonded structures of (OA)2-. Their stability has been analyzed in terms of the stability of the involved conformers, the energetic penalty for deformation of these conformers to the geometry of the dimer, and the two-body interaction energy between the deformed HOA˙ and (OA-H)-. There are at least seven isomers of (OA)2- with stabilization energies in the range of 1.26-1.39 eV. These energies are dominated by attractive two-body interaction energies. The anions are vertically bound electronically by 3.0-3.4 eV and adiabatically bound by at least 1.6 eV. The computational predictions are consistent with the anion photoelectron spectrum of (OA)2-. The spectrum consists of a broad feature, with an onset of 2.5 eV and spanning to 4.3 eV. The electron vertical detachment energy (VDE) is assigned to be 3.3 eV.

An ab Initio Study on the Structure, Energetics, and Spectra of Cl-···(CO2)n Clusters.

Structures, energetics, and photoelectron spectral properties of Cl-···(CO2)n (n = 1-8) clusters are studied by ab initio electronic structure methods, namely, Møller-Plesset second-order perturbation theory (MP2) correlated consistent, aug-cc-pvtz basis functions. The most stable structure for each size is evaluated by using both bottom-up and top-down approaches. It is observed that CO2 molecules approach to the chloride anion in an asymmetric way except for Cl-···(CO2)8 cluster. We do observe the applicability of the simple classical electrostatic model for charge-quadrupole interactions to the solvation of the chloride anion by the solvent CO2. Both vertical electron detachment energies and solvation energies are calculated for all the clusters at the MP2 level. We do observe an excellent agreement between theory and experiment for the vertical detachment energy, solvation energy, and gas phase detachment energy of chloride anion. It is also observed that the detachment energy of the chloride anion is increased by 4.09 eV due to the solvation effect of bulk CO2 and it is quite small in contrast to the increase of 5.29 eV due to the solvation effect of polar solvent, water.

Comment on "Are polynuclear superhalogens without halogen atoms probable? A high-level ab initio case study on triple-bridged binuclear anions with cyanide ligands" [J. Chem. Phys. 140, 094301 (2014)

For the vertical electron detachment energies of triply-bridged Mg2(CN)5- superhalides, the Outer Valence Green Function (OVGF) yields results similar to those of the coupled-cluster singles and doubles plus approximate triples, or CCSD(T), method. Invalid comparisons between states with different symmetry or localization properties underlie the assertion of Yin et al that OVGF produces large discrepancies with respect to CCSD(T) for several isomers of Mg2(CN)5-.