Adiabatic Electron Detachment Energies Research Articles

The low-lying electronic states of YO2− and YO2: A computational study

• The vertical excitation spectra of YO 2 – and YO 2 were calculated. • Several bound anionic states of YO 2 – were found. • Electron detachment energies to low-lying doublet states of YO 2 were obtained. The low-lying electronic states of YO 2 − and YO 2 were studied using the SAC-CI theory. The vertical excitation spectra of YO 2 − and YO 2 were calculated. For YO 2 − , the X 1 A 1 state, five valence-bound singlet–triplet pair states (2 1 A 1 /1 3 A 1 , 1 1 A 2 /1 3 A 2 , 1 1 B 1 /1 3 B 1 , 1 1 B 2 /1 3 B 2 , and 2 1 B 2 /2 3 B 2 ), and one dipole-bound singlet–triplet pair states ( 1 B 2 (DB)/ 3 B 2 (DB)) were investigated. For YO 2 , the X 2 B 2 , 1 2 A 1 /2 2 A', 2 2 A 1 , 1 2 A 2 , 1 2 B 1 /1 2 A“, and 2 2 B 2 states were studied. The geometries of these anionic and neutral states were optimized. The adiabatic electron detachment energies from the anionic states to the neutral states can be obtained from these computed results. The vertical electron detachment energies from the X 1 A 1 state of YO 2 − to the low-lying doublet states of YO 2 were calculated and compared with previous experimental photoelectron spectra. Density functional theories (B3LYP, BPW91, and BP86) were also employed to compute the low-lying electronic states of YO 2 – and YO 2 for comparison.

Diffusion Monte Carlo method on small boron clusters using single- and multi- determinant-Jastrow trial wavefunctions.

Multireference character in some small boron clusters could be significant, and a previous all-electron fixed-node diffusion quantum Monte Carlo (FN-DMC) calculation with the single-determinant-Jastrow (SDJ) trial wavefunction shows that the atomization energy (AE) of B4 + is overestimated by about 1.4 eV compared with the coupled cluster method with single, doubles, and perturbative triples [CCSD(T)] results. All-electron FN-DMC calculations and those with the pseudopotential (PP) using SDJ and multi-determinant-Jastrow (MDJ) trial wavefunctions with B3LYP orbitals as well as CC calculations at different levels are carried out on Bn Q (n = 1-5, Q = -1, 0, 1) clusters. The obtained FN-DMC energies indicate that the node error of the employed SDJ trial wavefunction in all-electron calculations is different from that with the PP for some clusters. The error of AEs and dissociation energies (DEs) from all-electron FN-DMC calculations is larger than that with the PP when the SDJ trial wavefunction is employed, while errors of CC methods do not depend on whether the PP is used. AEs and DEs of the boron clusters are improved significantly when MDJ trial wavefunctions are used in both all-electron calculations and those with the PP, and their error is similar to that of CCSD(T) compared with CCSDT(Q) results. On the other hand, reasonable adiabatic electron detachment energies (ADEs) and ionization potentials (AIPs) are achieved with FN-DMC using SDJ trial wavefunctions and MDJ is less effective on ADEs and AIPs. Furthermore, the relative energy between two structures of B9 - is predicted reliably with FN-DMC using the SDJ trial wavefunction and the effect of MDJ is negligible, while density functional theory results using different exchange-correlation functionals differ significantly.

Magnesium-Based Oxyfluoride Superatoms: Design, Structure, and Electronic Properties.

The ability of mixed ligands to form stable dinuclear and trinuclear magnesium-based superatoms has been investigated theoretically. The Mg2F5-2 mO m and Mg3F7-2 mO m systems (where m = 1-3) were found able to form stable and strongly bound anionic clusters, and those assumptions were validated by (i) the analysis of the geometrical stability; (ii) the estimated Gibbs free energies for the most probable disproportion paths these clusters might be vulnerable to (which allows examining their thermodynamic stabilities); (iii) the localization of the electron density; and (iv) the adiabatic electron affinity (AEA), vertical electron detachment energy (VDE), and adiabatic electron detachment energy (ADE) values calculated for the studied systems. It is demonstrated that the stability of the anionic daughters of these clusters increases with the number of electronegative ligands, and Mg nF2 n+1-2 mO m- ( n = 2, 3; m = 1-3) clusters are stable against electron emission. The largest electron binding energy was found for the Mg3F5O- anion (VDE = 6.826 eV). The strong VDE dependence on (i) the geometrical structure, (ii) the number of central atoms, (iii) ligand type, and (iv) bonding/antibonding character of the highest molecular orbital (HOMO) was also remarked upon and discussed.

PrB7- : A Praseodymium-Doped Boron Cluster with a PrII Center Coordinated by a Doubly Aromatic Planar η7 -B73- Ligand.

The structure and bonding of a Pr-doped boron cluster (PrB7- ) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB7- is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB7 . Global minimum searches and comparison between experiment and theory show that PrB7- has a half-sandwich structure with C6v symmetry. Chemical bonding analyses show that PrB7- can be viewed as a PrII [η7 -B73- ] complex with three unpaired electrons, corresponding to a Pr (4f2 6s1 ) open-shell configuration. Upon detachment of the 6s electron, the neutral PrB7 cluster is a highly stable PrIII [η7 -B73- ] complex with Pr in its favorite +3 oxidation state. The B73- ligand is found to be highly stable and doubly aromatic with six delocalized π and six delocalized σ electrons and should exist for a series of lanthanide MIII [η7 -B73- ] complexes.

PrB7−: A Praseodymium‐Doped Boron Cluster with a PrII Center Coordinated by a Doubly Aromatic Planar η7‐B73− Ligand

AbstractThe structure and bonding of a Pr‐doped boron cluster (PrB7−) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB7− is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB7. Global minimum searches and comparison between experiment and theory show that PrB7− has a half‐sandwich structure with C6v symmetry. Chemical bonding analyses show that PrB7− can be viewed as a PrII[η7‐B73−] complex with three unpaired electrons, corresponding to a Pr (4f26s1) open‐shell configuration. Upon detachment of the 6s electron, the neutral PrB7 cluster is a highly stable PrIII[η7‐B73−] complex with Pr in its favorite +3 oxidation state. The B73− ligand is found to be highly stable and doubly aromatic with six delocalized π and six delocalized σ electrons and should exist for a series of lanthanide MIII[η7‐B73−] complexes.

A Joint Experimental and Computational Study of the Negative Ion Photoelectron Spectroscopy of the 1-Phospha-2,3,4-triazolate Anion, HCPN3(.).

We report here the results of a combined experimental and computational study of the negative ion photoelectron spectroscopy (NIPES) of the recently synthesized, planar, aromatic, HCPN3(-) ion. The adiabatic electron detachment energy of HCPN3(-) (electron affinity of HCPN3(•)) was measured to be 3.555 ± 0.010 eV, a value that is intermediate between the electron detachment energies of the closely related (CH)2N3(-) and P2N3(-) ions. High level electronic structure calculations and Franck-Condon factor (FCF) simulations reveal that transitions from the ground state of the anion to two nearly degenerate, low-lying, electronic states, of the neutral HCPN3(•) radical are responsible for the congested peaks at low binding energies in the NIPE spectrum. The best fit of the simulated NIPE spectrum to the experimental spectrum indicates that the ground state of HCPN3(•) is a 5π-electron (2)A″ π radical state, with a 6π-electron, (2)A', σ radical state being at most 1.0 kcal/mol higher in energy.

Negative Ion Photoelectron Spectroscopy Reveals Remarkable Noninnocence of Ligands in Nickel Bis(dithiolene) Complexes [Ni(dddt)2](-) and [Ni(edo)2](-).

[Ni(dddt)2](-) (dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) and [Ni(edo)2](-) (edo = 5,6-dihydro-1,4-dioxine-2,3-dithiolate) are two donor-type nickel bis(dithiolene) complexes, with the tendency of donating low binding energy electrons. These two structurally similar complexes differ only with respect to the outer atoms in the ligand framework where the former has four S atoms while the latter has four O atoms. Herein, we report a negative ion photoelectron spectroscopy (NIPES) study on these two complexes to probe the electronic structures of the anions and their corresponding neutrals. The NIPE spectra exhibit the adiabatic electron detachment energy (ADE) or, equivalently, the electron affinity (EA) of the neutral [Ni(L)2](0) to be relatively low for this type of complexes, 2.780 and 2.375 eV for L = dddt and edo, respectively. The 0.4 eV difference in ADEs shows a significant substitution effect for sulfur in dddt by oxygen in edo, i.e., noninnocence of the ligands, which has decreased the electronic stability of [Ni(edo)2](-) by lowering its electron binding energy by ∼0.4 eV. The observed substitution effect on gas-phase EA values correlates well with the measured redox potentials for [Ni(dddt)2](-/0) and [Ni(edo)2](-/0) in solutions. The singlet-triplet splitting (ΔEST) of [Ni(dddt)2](0) and [Ni(edo)2](0) is also determined from the spectra to be 0.57 and 0.53 eV, respectively. Accompanying DFT calculations and molecular orbital (MO) composition analyses show significant ligand contributions to the redox MOs and allow the components of the orbitals involved in each electronic transition and spectral assignments to be identified.

Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission.

We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl6 (2-) dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl6 (2-) ⋅ thymine and PtCl6 (2-) ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)4 (2-) ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl6 (2-) ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN)4 (2-) ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a "dynamic tag" which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to allow autodetachment.

Electron detachment and fragmentation of laser-excited rotationally hotAl4−

Absolute photoabsorption cross sections of negatively charged tetra-atomic aluminum clusters have been measured for photon energies between 1.8 and 2.7 eV. The experiment used the depletion technique in combination with an electrostatic ion-beam trap, in which ${{\mathrm{Al}}_{4}}^{\ensuremath{-}}$ ions produced in a sputter ion source were stored for 90 ms before being subjected to a short laser pulse. Moreover, the competition between one-atom fragmentation and electron emission of the laser-excited ${{\mathrm{Al}}_{4}}^{\ensuremath{-}}$ has been measured. These measurements show that fragmentation dominates electron emission at all photon energies below the electron attachment energy of $\ensuremath{\sim}2.2$ eV, even though the fragmentation energy is expected to be 10%--20% higher than the electron attachment energy. These findings, when taken together with the delayed-electron and fragmentation yields observed in a previous measurement [O. Aviv et al., Phys. Rev. A 83, 023201 (2011)], can be well explained within the statistical phase-space theory for unimolecular decays assuming the ${{\mathrm{Al}}_{4}}^{\ensuremath{-}}$ ions to be rotationally hot. The analysis permits the determination of the adiabatic electron detachment energy of ${{\mathrm{Al}}_{4}}^{\ensuremath{-}}$ to be ${E}_{\text{ad}}=(2.18\ifmmode\pm\else\textpm\fi{}0.02)$ eV and the one-atom fragmentation energy to be ${D}_{0}=(2.34\ifmmode\pm\else\textpm\fi{}0.05)$ eV. Moreover, two direct $s$-wave ionization channels are observed with threshold energies of $(2.18\ifmmode\pm\else\textpm\fi{}0.02)$ eV and $(2.45\ifmmode\pm\else\textpm\fi{}0.02)$ eV.

Electron Detachment as a Probe of Intrinsic Nucleobase Dynamics in Dianion-Nucleobase Clusters: Photoelectron Spectroscopy of the Platinum II Cyanide Dianion Bound to Uracil, Thymine, Cytosine, and Adenine.

We report the first low-temperature photoelectron spectra of isolated gas-phase complexes of the platinum II cyanide dianion bound to nucleobases. These systems are models for understanding platinum-complex photodynamic therapies, and a knowledge of the intrinsic photodetachment properties is crucial for characterizing their broader photophysical properties. Well-resolved, distinct peaks are observed in the spectra, consistent with complexes where the Pt(CN)4(2-) moiety is largely intact. Adiabatic electron detachment energies for the dianion-nucleobase complexes are measured to be 2.39-2.46 eV. The magnitudes of the repulsive Coulomb barriers of the complexes are estimated to be between 1.9 and 2.1 eV, values that are lower than for the bare Pt(CN)4(2-) dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four dianion-nucleobase complexes and also in the 266 nm spectra of the Pt(CN)4(2-)·thymine and Pt(CN)4(2-)·adenine complexes. The selective excitation of these features in the 266 nm spectra is attributed to one-photon excitation of [Pt(CN)4(2-)·thymine]* and [Pt(CN)4(2-)·adenine]* long-lived excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment signals. We attribute the delayed electron detachment bands observed here for Pt(CN)4(2-)·thymine and Pt(CN)4(2-)·adenine but not for Pt(CN)4(2-)·uracil and Pt(CN)4(2-)·cytosine to fundamental differences in the individual nucleobase photophysics following 266 nm excitation. This indicates that the Pt(CN)4(2-) dianion in the clusters can be viewed as a "dynamic tag" which has the propensity to emit electrons when the attached nucleobase displays a long-lived excited state.

Photoelectron spectroscopy and theoretical studies of gaseous uranium hexachlorides in different oxidation states: UCl6 (q-) (q = 0-2).

Uranium chlorides are important in actinide chemistry and nuclear industries, but their chemical bonding and many physical and chemical properties are not well understood yet. Here, we report the first experimental observation of two gaseous uranium hexachloride anions, UCl6 (-) and UCl6 (2-), which are probed by photoelectron spectroscopy in conjunction with quantum chemistry calculations. The electron affinity of UCl6 is measured for the first time as +5.3 eV; its second electron affinity is measured to be +0.60 eV from the photoelectron spectra of UCl6 (2-). We observe that the detachment cross sections of the 5f electrons are extremely weak in the visible and UV energy ranges. It is found that the one-electron one-determinental molecular orbital picture and Koopmans' theorem break down for the strongly internally correlated U-5f(2) valence shell of tetravalent U(+4) in UCl6 (2-). The calculated adiabatic and vertical electron detachment energies from ab initio calculations agree well with the experimental observations. Electronic structure and chemical bonding in the uranium hexachloride species UCl6 (2-) to UCl6 are discussed as a function of the oxidation state of U.

Examining the amine functionalization in dicarboxylates: photoelectron spectroscopy and theoretical studies of aspartate and glutamate.

Aspartate (Asp(2-)) and glutamate (Glu(2-)), two doubly charged conjugate bases of the corresponding amino acids, were investigated using low-temperature negative ion photoelectron spectroscopy (NIPES) and ab initio calculations. The effect of amine functionalization was studied by a direct comparison to the parent dicarboxylate species ((-)CO2-(CH2)n-CO2(-), DCn(2-)), succinate (DC2(2-)) and propionate (DC3(2-)). Experimentally, the addition of the amine group for the n = 2 case (DC2(2-), Asp(2-)) significantly improves the stability of the resultant Asp(2-) dianionic species, albeit that NIPES shows only a small increase in adiabatic electron detachment energy (ADE) (+0.05 eV). In contrast, for n = 3 (DC3(2-), Glu(2-)), a much larger ADE increase is observed (+0.15 eV). Similar results are obtained through ab initio calculations. The latter indicates that increased stability of Asp(2-) can be attributed to the lowering of the energy of the singlet dianion state due to hydrogen bonding effects. The effect of the amino group on the doublet monoanion state is more complicated and results in the weakening of the binding of the adjacent carboxylate group due to electronic structure resonance effects. This conclusion is confirmed by the analysis of NIPES results that show enhanced production of near-zero kinetic energy electrons observed experimentally for amine-functionalized species.

Theoretical and experimental studies of the interactions between Au2− and nucleobases

Combined anion photoelectron spectroscopy and relativistic quantum chemical studies are conducted on nucleobase-Au2(-) cluster anions. The vertical detachment energies of uracil-Au2(-) (UAu2(-)), thymine-Au2(-) (TAu2(-)), cytosine-Au2(-) (CAu2(-)), adenine-Au2(-) (AAu2(-)), guanine-Au2(-) (GAu2(-)) are determined to be 2.71 ± 0.08 eV, 2.74 ± 0.08 eV, 2.67 ± 0.08 eV, 2.65 ± 0.08 eV and 2.73 ± 0.08 eV, respectively, based on the measured photoelectron spectra. Through computational geometry optimizations we have identified the lowest-energy structures of these nucleobase-Au2(-) cluster anions. The structures are further confirmed by comparison of theoretically calculated vertical and adiabatic electron detachment energies with experimental measurements. The results reveal that the Au2(-) anion remains as an intact unit and interacts with the nucleobases through N-HAu or C-HAu nonconventional hydrogen bonds. The nucleobase-Au2(-) cluster anions have relatively weak N-HAu hydrogen bonds and strong C-HAu hydrogen bonds compared to those of nucleobase-Au(-) anions.

Hydrogen-Bond Networks: Strengths of Different Types of Hydrogen Bonds and An Alternative to the Low Barrier Hydrogen-Bond Proposal

We report quantifying the strengths of different types of hydrogen bonds in hydrogen-bond networks (HBNs) via measurement of the adiabatic electron detachment energy of the conjugate base of a small covalent polyol model compound (i.e., (HOCH2CH2CH(OH)CH2)2CHOH) in the gas phase and the pKa of the corresponding acid in DMSO. The latter result reveals that the hydrogen bonds to the charged center and those that are one solvation shell further away (i.e., primary and secondary) provide 5.3 and 2.5 pKa units of stabilization per hydrogen bond in DMSO. Computations indicate that these energies increase to 8.4 and 3.9 pKa units in benzene and that the total stabilizations are 16 (DMSO) and 25 (benzene) pKa units. Calculations on a larger linear heptaol (i.e., (HOCH2CH2CH(OH)CH2CH(OH)CH2)2CHOH) reveal that the terminal hydroxyl groups each contribute 0.6 pKa units of stabilization in DMSO and 1.1 pKa units in benzene. All of these results taken together indicate that the presence of a charged center can provide a powerful energetic driving force for enzyme catalysis and conformational changes such as in protein folding due to multiple hydrogen bonds in a HBN.

Face-Capping μ3-BO in B6(BO)7–: Boron Oxide Analogue of B6H7– with Rhombic 4c–2e Bonds

Using the first-principle approaches, we predict a B6(BO)7(-) cluster with a face-capping μ(3)-BO, which is the boron oxide analogue of closo-B6H7(-) with a face-capping μ(3)-H. Detailed topological analysis of electron density clearly reveals the existence of three rhombic 4c-2e bonds around the B/H apex in both C3v B6(BO)7(-) and C3v B6H7(-), which possesses similar electron densities at their bond and ring critical points. The adaptive natural density partitioning (AdNDP) analysis provides a direct and visual picture of the B-B-B-B/H 4c-2e bonds for the first time. Adiabatic and vertical electron detachment energies of the concerned monoanions are calculated to facilitate their future photoelectron spectroscopy measurements and characterizations. The presence of the B6(BO)7(-) and B6H7(-) clusters extends the BO/H isolobal analogy to the whole μ(n)-BO/H series (n = 1, 2, and 3) and enriches the chemistry of boronyl.

Theoretical studies of sulfite – sulfur dioxide clusters, SO32−(SO2)n: structure and stability of SnO2n+1 anions, n = 1–5

Density functional calculations using the B3PW91 functional with the 6-311+G(3df) basis set were performed on the addition of n = 1–4 SO2 molecules to SO3− and SO32−. Geometry optimizations were performed for a large number of possible structures. At n = 4, the dianionic cluster becomes adiabatically more stable than the monoanionic one, with an adiabatic electron detachment energy of 0.30 eV. Monoanionic clusters are characterized by the O–S–O–SO3 moiety having long O–S bonds to SO2 molecules. Dianionic clusters, however, prefer S–S bonding of O3S–O–S(O) with SO2.

First principles gas phase study of the structures, energetics and spectroscopic parameters of aluminium antimonide, Al x Sb y (x + y = 3, 5), clusters

Theoretical methods (DFT/B3LYP and MP2) have been used to optimize the geometries of the Al x Sb y (x + y = 3, 5) clusters and their anions. Single point energy computations at CCSD(T) level have also been performed using the optimized B3LYP and MP2 structures. The basis sets used for Al and Sb atoms are 6-311+G(2d) and LANL2DZdp ECP, respectively. Harmonic vibrational frequency computations were carried out to confirm the nature of the stationary points. We report the structural and spectroscopic parameters of the named clusters. We also report the relative energy of the clusters, the vertical electron detachment energy, the adiabatic electron detachment energy and the adiabatic electron affinity. The most stable structures at the CCSD(T)//MP2 level are, the D ∞h linear structure (AlSb2) and the C 2v V-bent structure (AlSb 2 − ), the C 2v V-bent structure (Al2Sb and its anion), the C 2v edge-capped tetrahedron (Al2Sb3 and its anion), the C 2v trigonal bipyramidal structure (Al3Sb2 and its anion), the C 4v square pyramidal (AlSb4) and a C 2v ground structure for its anion, the C 2v planar trapezoidal structure (Al4Sb) and the C 2v edge-capped tetrahedron (Al4Sb−). The adiabatic electron affinities calculated at the CCSD(T)//MP2 level are 2.17 eV (AlSb2), 2.17 eV (Al2Sb), 2.38 eV (Al2Sb3), 2.76 eV (Al3Sb2), 2.21 eV (AlSb4) and 2.03 eV (Al4Sb). The findings of this research are analysed, discussed and compared with the analogous picnogenides clusters.

Probing the Electronic Structure and Chemical Bonding in Tricoordinate Uranyl Complexes UO2X3– (X = F, Cl, Br, I): Competition between Coulomb Repulsion and U–X Bonding

While uranyl halide complexes [UO2(halogen)n](2-n) (n = 1, 2, 4) are ubiquitous, the tricoordinate species have been relatively unknown until very recently. Here photoelectron spectroscopy and relativistic quantum chemistry are used to investigate the bonding and stability of a series of gaseous tricoordinate uranyl complexes, UO2X3(-) (X = F, Cl, Br, I). Isolated UO2X3(-) ions are produced by electrospray ionization and observed to be highly stable with very large adiabatic electron detachment energies: 6.25, 6.64, 6.27, and 5.60 eV for X = F, Cl, Br, and I, respectively. Theoretical calculations reveal that the frontier molecular orbitals are mainly of uranyl U-O bonding character in UO2F3(-), but they are from the ligand valence np lone pairs in the heavier halogen complexes. Extensive bonding analyses are carried out for UO2X3(-) as well as for the doubly charged tetracoordinate complexes (UO2X4(2-)), showing that the U-X bonds are dominated by ionic interactions with weak covalency. The U-X bond strength decreases down the periodic table from F to I. Coulomb barriers and dissociation energies of UO2X4(2-) → UO2X3(-) + X(-) are calculated, revealing that all gaseous dianions are in fact metastable. The dielectric constant of the environment is shown to be the key in controlling the thermodynamic and kinetic stabilities of the tetracoordinate uranyl complexes via modulation of the ligand-ligand Coulomb repulsions.

Evolution of the structure and electronic properties of neutral and anion [formula omitted] (n = 1–7, μ = 0, −1) clusters: A comprehensive analysis

The structural evolution, stabilities and electronic properties of neutral and anionic FeSnμ (n=1–7, μ=0, −1) clusters have been investigated with the aid of previous photoelectron spectroscopy (PES) and density functional theory. For each sized iron–sulfur cluster, the low-lying isomers are generated using Saunders “kick” global optimization method. The theoretical vertical and adiabatic electron detachment energies (VDEs and ADEs) were compared with the experimental values to corroborate the ground state structures. The results indicate that the combination of photoelectron spectroscopy experiments and density functional theory calculation is powerful for obtaining the accurate electronic structures. By calculating the binding energies, fragmentation energies and second difference energies, we found FeS, FeS4, FeS2- and FeS4- clusters have the relative stronger stability. Furthermore, the two equal maxima of HOMO–LUMO gaps (2.81eV) for the most stable configurations appear at FeS and FeS2-. Additionally, to probe into the electron transfer information and redistribution of electron density induced by bonding, the natural population analysis (NPA) and electron density difference are investigated and discussed.

Photoelectron Spectroscopy of Palladium(I) Dimers with Bridging Allyl Ligands

The dianionic PdI dimers [TBA]2[(TPPMS)2Pd2(μ-C3H5)2] (1) [TBA = tetrabutylammonium, TPPMS = PPh2(3-C6H4SO3)−] and [TBA]2[(TPPMS)2Pd2(μ-C3H5)(μ-Cl)] (2), containing two bridging allyl ligands and one bridging allyl ligand and one bridging chloride ligand, respectively, were synthesized. The electronic structures of these complexes were investigated by combining electrospray mass spectrometry with gas phase photodetachment photoelectron spectroscopy. The major difference between the photoelectron spectra of the anions of 1 and 2 is the presence of a low-energy detachment band with an adiabatic electron detachment energy of 2.44(6) eV in 1, which is not present in 2. The latter has a much higher adiabatic electron detachment energy of 3.24(6) eV. Density functional theory calculations suggest that this band is present in 1 due to electron detachment from the out-of-phase combination of the π2 orbitals, which are localized on the terminal carbon atoms of the bridging allyl ligands. In 2, the Pd centers stabi...