Adiabatic Detachment Energies Research Articles

Structural evolution and bonding properties of Nb1-2Gen-/0 (n = 3-7) clusters: Anion photoelectron spectroscopy and theoretical calculations.

This study presents a collaborative experimental and theoretical investigation into the structures and electronic properties of niobium-doped germanium clusters. Anion photoelectron spectra for Nb1-2Gen- (n = 3-7) clusters were acquired using 266nm photon energies, enabling the determination of adiabatic detachment energies and vertical detachment energies. In conjunction with these experimental measurements, density functional theory (DFT) calculations were conducted to validate the experimentally obtained electron detachment energies and elucidate the geometric and electronic structures of each anionic cluster. The agreement between DFT calculations and experimental data establishes a solid foundation for assessing the structural evolution and electronic properties of niobium-doped germanium clusters. It is noted that both neutral and anionic clusters exhibit predominantly similar overall structural characteristics, with the exception of Nb2Ge6- and Nb2Ge6. Furthermore, this investigation emphasizes the exceptional chemical stability of the D3d symmetric chair-shaped structure in Nb2Ge6-, providing insights into its bonding characteristics.

Probing the geometric and electronic structures of the transition metal oxides RhOn–1/0 (n = 1–4) clusters

The photoelectron spectroscopies of RhOn– (n = 1–2) were obtained via using the photoelectron velocity-map imaging (PE-VMI) approach. The experimental values of the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) for RhO– were reported to be 1.58 ± 0.02 eV. The experimental AED and VDE values of RhO2– were reported to be 2.70 ± 0.02 eV and 2.79 ± 0.02 eV, respectively. The vibrational frequencies of RhO– and RhO2– measured from photoelectron spectra (PES) were 817(76) cm−1 and 932(55) cm−1, respectively. Based on the density functional theory (DFT), the RhOn–1/0 (n = 1–4) clusters were investigated. The optimized configurations of corresponding ground states and low-lying clusters were discovered. Meanwhile, the simulated photoelectron spectroscopy (PES) of RhOn– (n = 1–4) and the theoretical ADE and VDE values of RhOn– (n = 1–4) clusters were unveiled to assist future experimental studies of Rhodium oxide clusters. Moreover, the associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized to investigate the chemical bonding in these groups.

Unveiling geometric and electronic structures of NbSi4−/0 clusters and electron detachments of the anionic cluster: A quantum chemical investigation

AbstractThis article presents computational insights into the geometric and electronic structures of NbSi4−/0 clusters using density functional theory and the CASSCF/CASPT2 method. The anionic and neutral ground states are identified as the 1A′ and 2A′ states, respectively, within a trigonal bipyramidal isomer where the Nb atom occupies the equatorial position. The adiabatic detachment energy for the transition from the anionic ground state 1A′ to the neutral ground state 2A′ is estimated to be 2.30 eV. Additionally, an evaluation of the vertical detachment energies for transitions to the neutral states 12A′, 12A″, 22A′, 22A″, 32A′, 32A″, and 42A′ yields respective values of 2.42, 2.78, 2.94, 3.34, 3.86, 4.08, and 4.28 eV. These computed electron detachment energies successfully account for all five bands observed in the photoelectron spectrum of the anionic cluster. Furthermore, the Franck–Condon factor simulations reveal extensive vibrational progressions associated with the transition to the neutral ground state 12A′, manifesting as an unresolved broad band at 2.41 eV in the spectrum.

Unraveling the mystery of solvation-dependent fluorescence of fluorescein dianion using computational study.

Fluorescein, one of the brightest fluorescent dye molecules, is a widely used fluorophore for various applications from biomedicine to industry. The dianionic form of fluorescein is responsible for its high fluorescence quantum yield. Interestingly, the molecule was found to be nonfluorescent in the gas phase. This characteristic is attributed to the photodetachment process, which out-competes the fluorescence emission in the gas phase. In this work, we show that the calculated vertical and adiabatic detachment energies of fluorescein dianion in the gas and solvent phases account for the drastic differences observed in their fluorescence characteristics. The functional dependence of these detachment energies on the dianion's microsolvation was systematically investigated. The performance of different solvent models was also assessed. The higher thermodynamic stability of fluorescein dianion over the monoanion doublet in the solvent phase plays a crucial role in quenching photodetachment and activating the radiative channel with a high fluorescence quantum yield.

Semiempirical Approach to the Fukui Function Analysis of Uric Acid under Different pH Conditions.

Analytic Fukui functions calculated at a first-principles level are combined with experimental pKa values and the calculation of tautomerization energies to obtain the effective regioselectivity of uric acid toward electron-transfer reactions under different pH conditions. Second-order electron binding energies are also computed to determine which of the tautomers is more likely to participate in the electron transfer. A comparison of vertical and adiabatic proton detachment energies allows us to conclude that tautomerization is not mediating deprotonation and that two monoanionic species are of comparable relevance. The main difference between these monoanionic species is the ring that has been deprotonated. Both monoanionic species are produced from a single neutral tautomer and mainly produce a single dianionic tautomer. As a method for the analysis of systems affected by pH such as uric acid, we propose to plot condensed Fukui functions versus pH, allowing us to draw the effect of pH on the regioselectivity of electron transfer in a single image.

Calculations on the structures of ScGenSc0/- (n=3,4) clusters

The structures of SiGenSc0/− (n = 3, 4) clusters were investigated by a combination of quantum chemical calculations, including the genetic algorithm (GA), the Perdew-Burke-Ernzerhof PBE functional, and coupled- cluster calculations (CCSD(T)). The geometrical structure, relative energy, harmonic vibrational frequency, adiabatic detachment energies were reported. The PBE functional is in good agreement with the CCSD(T) method. The stable structure of the SiGenSc0/− (n = 3, 4) clusters have a low spin multiplicity. The larger cluster can be formed by adsorbing the atom into the smaller cluster. The obtained results can contribute to the orientation of the nanomaterial formation for gas adsorption.

Theoretical prediction for growth behavior and electronic properties of monoanionic Ru2Gen− (n = 3–20) clusters

We present a detailed theoretical study on the structural and electronic properties of monoanionic Ru2Gen− (n = 3–20) clusters using comprehensive genetic algorithm combined with density functional theory (CGA-DFT). It is shown that the geometrical growth patterns of the ground state Ru2Gen− clusters are polyhedral pyramidal structures with n ≤ 9 and gradually to form pentagonal prism-based structures with two endohedral Ru atoms from 10 ≤ n ≤ 15, then the structures evolve into a oblate cage-like configuration with two Ru atoms in center from cluster sizes n ≥ 16. In general, one extra electron will influence the geometric structures of Ru2Gen clusters to compare with their neutral ones we have studied. Based on the obtained ground state structures, we find that the clusters of Ru2Ge10−, Ru2Ge12− and Ru2Ge14− have relatively higher structural and chemical stability in which Ru2Ge14− is more prominent through the analysis of binding energy, second order of energy difference and highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap. Furthermore, we analyzed natural charge, natural electronic configuration, the frontier molecular orbitals and orbital composition to verify the clusters of Ru2Gen− with n = 10, 12, 14 and 16 have relatively higher chemical stability owning to the less contribution of Ru-d orbitals. In addition, the clusters of Ru2Ge3−, Ru2Ge4−, Ru2Ge6−, Ru2Ge10− and Ru2Ge16− have magnetic moment of 3 μB, while others are 1 μB. And also the vertical detachment energy (VDE) and adiabatic detachment energy (ADE) for all ground state clusters are computed to support future experiment.

Observation of unsaturated platinum carbenes Pt2C2n - (n = 1-3) clusters: A photoelectron imaging spectroscopic and theoretical study.

The structural and bonding properties of the Pt2C2n - (n = 1-3) complexes have been investigated by mass-selected photoelectron velocity-map imaging spectroscopy with quantum chemical calculations. The adiabatic detachment energies and vertical detachment energies of Pt2C2n - have been obtained from the measured photoelectron imaging spectra. Theoretical results indicate that the lowest-energy isomers of Pt2C2n - (n = 1-3) possess linear chain-shaped configurations. The binding motif in the most stable isomer of Pt2C2 - has a linear cumulenic structure with a Pt=C=C=Pt configuration, and the structural characteristic persists up to all the lowest-energy isomers of the Pt2C4 - and Pt2C6 - anions. The chemical bonding analyses indicate that the Pt2C2n - (n = 1-3) complexes have multicenter two-electron characteristics.

Guanosine Dianions Hydrated by One to Four Water Molecules.

Intermolecular interactions such as those present in molecule···water complexes may profoundly influence the physicochemical properties of molecules. Here, we carried out an experimental–computational study on doubly deprotonated guanosine monophosphate···water clusters, [dGMP – 2H]2–·nH2O (n = 1–4), using a combination of negative anion photoelectron spectroscopy (NIPES) with molecular dynamics (MD) and quantum chemical (QM) calculations. Successive addition of water molecules to [dGMP – 2H]2– increases the experimental adiabatic detachment (ADE) and vertical detachment energy (VDE) by 0.5–0.1 eV, depending on the cluster size. In order to choose the representative conformations, we combined MD simulations with a clustering procedure to identify low energy geometries for which ADEs and VDEs were computed at the CAM-B3LYP/6-31++G(d,p) level. Our results demonstrate that the assumed approach leads to sound geometries and energetics of the studied microsolvates since the calculated ADEs and VDEs are in pretty good agreement with the experimental characteristics. The evolution of hydrogen bonding with cluster size indicates the possibility of the occurrence of proton transfer for clusters comprising a larger number of water molecules.

Photoelectron spectroscopy and density functional theory calculations of binary Vn C3/− (n = 1 − 6) clusters

Transition metal carbides have been shown to exhibit good catalytic performance that depends on their compositions and morphologies, and understanding such catalytic properties requires knowledge of their precise geometry, determination of which is challenging, particularly for clusters formed by multiple elements. In this study, we investigate the geometries and electronic structures of binary VnC3− (n=1−6) clusters and their neutrals using photoelectron spectroscopy and theoretical calculations based on density functional theory. The adiabatic detachment energies of VnC3−, or equally, the electron affinities of VnC3, have been determined from the measured photoelectron spectra. Theoretical calculations reveal that the carbon atoms become separate when the number of V atoms increases in the clusters, i.e., the C−C interactions present in small clusters are replaced by V−C and/or V−V interactions in larger ones. We further explore the composition dependent formation of cubic or cube-like structures in 8-atom VnCm(n+m=8) clusters.

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.

Cryogenic Vibrationally Resolved Photoelectron Spectroscopy of OH-(H2O): Confirmation of Multidimensional Franck-Condon Simulation Results for the Transition State of the OH + H2O Reaction.

We present a transition state spectroscopic study of the OH + H2O reaction using the experimental technique of cryogenic negative ion photoelectron spectroscopy (NIPES). The recorded NIPE spectrum at 193 nm exhibits multiple vibrational progressions that include excitations to the shared H atom antisymmetric stretching mode with an interval of 0.32 eV as well as other progressions, mainly involving the H bending and O···O symmetric stretching modes. The vertical detachment energy (VDE) was measured at 3.53 eV, whereas an upper limit for the adiabatic detachment energy (ADE) was estimated at 2.90 eV. These values are in excellent agreement with the theoretically computed values of 3.51 and 2.87 eV, respectively, obtained at the CCSD(T)/aug-cc-pV5Z level of theory. The recorded NIPE spectrum is in very good agreement when compared to the one recently reported from four-dimensional Franck-Condon simulations, in which a similar spectral profile was predicted. Besides observing the ground state, we identified a charge-transfer excited state in the form of [OH-(H2O)+] with a relative energy of 1.39 eV, well matching the previous prediction of 1.36 eV.

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.

Transition-metal-like bonding behaviors of a boron atom in a boron-cluster boronyl complex [(η7-B7)-B-BO

Boron displays many unusual structural and bonding properties due to its electron deficiency. Here we show that a boron atom in a boron monoxide cluster (B9O−) exhibits transition-metal-like properties. Temperature-dependent photoelectron spectroscopy provided evidence of the existence of two isomers for B9O−: the main isomer has an adiabatic detachment energy (ADE) of 4.19 eV and a higher energy isomer with an ADE of 3.59 eV. The global minimum of B9O− is found surprisingly to be an umbrella-like structure (C6v, 1A1) and its simulated spectrum agrees well with that of the main isomer observed. A low-lying isomer (Cs, 1A′) consisting of a BO unit bonded to a disk-like B8 cluster agrees well with the 3.59 eV ADE species. The unexpected umbrella-like global minimum of B9O− can be viewed as a central boron atom coordinated by a η7-B7 ligand on one side and a BO ligand on the other side, [(η7-B7)-B-BO]−. The central B atom is found to share its valence electrons with the B7 unit to fulfill double aromaticity, similar to that in half-sandwich [(η7-B7)-Zn-CO]− or [(η7-B7)-Fe(CO)3]− transition-metal complexes. The ability of boron to form a half-sandwich complex with an aromatic ligand, a prototypical property of transition metals, brings out new metallomimetic properties of boron.

Probing the geometric and electronic structures of the lanthanide oxide HoOn–1/0 (n = 1–3) clusters

The complex 4f and 5d orbits of lanthanide oxide clusters increases the complexity and difficulty in both theoretical and experimental research. Combining the photoelectron imaging spectroscopy and ab initio calculations, the structural and electronic properties of HoO– were studied. The adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of HoO– have been measured to be 1.31(3) eV and 1.42(2) eV, respectively. To determine the vibrational structure and observed spectral bands in the photoelectron spectrum, Franck-Condon simulation of the ground-state transition for HoO– has been performed. The fundamental frequency of ground-state HoO is estimated to be 893 ± 73 cm−1. Density functional method (DFT) was used to study the neutral and anionic clusters of HoOn–1/0 (n = 1–3), and the most stable cluster structures were obtained. Based on the DFT calculations, the theoretical ADEs and VDEs of anionic HoOn– (n = 1–3) clusters were obtained and the photoelectron spectra (PES) of HoOn– (n = 1–3) clusters were simulated, which might stimulate further experimental investigations on the Ho oxide clusters. In addition, the corresponding molecular orbitals (MOs) were also discussed to reveal the interaction between Ho and O atoms. This study can help us to understand the chemical bonding in Ho-containing molecules and will provide some light in their surface chemistry and photochemistry investigation.

Structures and properties of VB5−/0 clusters from density functional theory calculations

Density functional theory with the BPW91 functional and def2-TZVP basis sets was used to investigate the geometric structures of VB5−/0 clusters. By using the bee colony algorithm, 300 initial structures are created for the studied cluster. The geometry optimizations at the BPW91/def2-SVP level result in 18 low-lying isomers in quartet states for the anionic cluster. The results at the BPW91/def2-TZVP level show relative energies and vibrational frequencies for different spin states of 7 isomers of the anionic clusters and 6 isomers of the neutral cluster. It is found that the most stable isomers are A-VB5−/0 with non-planar pentagonal structure. The adiabatic detachment energy of the anionic cluster and the ionization energy of the neutral cluster are 1.93 and 7.36 eV.

Electronic structures of NbGen -/0/+ (n = 1-3) clusters from multiconfigurational CASPT2 and density matrix renormalization group-CASPT2 calculations.

Density functional theory and multiconfigurational CASPT2 and density matrix renormalization group DMRG-CASPT2 have been employed to study the low-lying states of NbGen -/0/+ (n = 1-3) clusters. With the DMRG-CASPT2 method, the active spaces are extended to a size of 20 orbitals. For most of the states, the CASPT2 relative energies are comparable with the DMRG-CASPT2 results. The leading configuration, bond distances, vibrational frequencies, and relative energies of the low-lying states of these clusters were calculated. The ground states of these clusters were computed to be 3 Δ, 4 Φ, and 5 Φ of NbGe-/0/+ ; 3 A2 , 4 B1 , and 3 B1 of cyclic-NbGe2 -/0/+ ; and 1 A', 12 A″ and 12 A'' (2 E), and 3 A″ of tetrahedral-NbGe3 -/0/+ isomers. For NbGe cluster, our calculations proposed that the 6 ∑ is almost degenerate with the 4 Φ with the CASPT2 and DMRG-CASPT2 relative energies of 0.05 and 0.06 eV. The adiabatic detachment energies of NbGen - (n = 1-3) clusters were estimated to be 1.46, 1.55, and 2.18 eV by the CASPT2 method. The relevant detachment energies of the anionic ground state and the ionization energies of the neutral ground states are evaluated at the CASPT2 level.

High-resolution anion photoelectron spectroscopy of cryogenically cooled 4-atom silicon carbides

High-resolution anion photoelectron spectra of cryogenically cooled , , and obtained using slow photoelectron velocity-map imaging (cryo-SEVI) are presented, providing insight into the geometries, energetics, and vibronic structure of the anionic and the neutral clusters. These spectra yield accurate vibrational frequencies for the neutral clusters. They also yield refined adiabatic detachment energies (ADEs) for the ground states of and of 1.5374(6) eV and 1.9019(4) eV, respectively, while the ADE of a low-lying isomer of is found to be 1.9050(7) eV. The cryo-SEVI spectra show that the ground state of is a distorted trapezoid, and represent the first confirmation of the distorted trapezoid structure of , the only low-lying isomer of this cluster with a permanent dipole moment. Additional transitions are observed from two low-lying anion isomers: a linear structure and a rhombus. The spectrum of , in combination with electronic structure calculations, suggests that the true ground state of is a ring structure with a transannular C–C bond, addressing a longstanding controversy surrounding this cluster. All three spectra exhibit Franck-Condon forbidden transitions; these are attributed to Herzberg-Teller coupling in and and autodetachment from an excited electronic state of .

Photoelectron Velocity Map Imaging Spectroscopic and Theoretical Study of Heteronuclear MNi(CO)7– (M = V, Nb, Ta)

A series of heteronuclear group 5 metal-nickel carbonyls MNi(CO)7- (M = V, Nb, Ta) have been generated via a laser ablation ion source and studied by photoelectron velocity-map imaging spectroscopy. Quantum chemical calculations have been performed to probe the electronic and geometric structures and help to assign the spectra. The adiabatic detachment energies (ADEs) and vertical detachment energies (VDEs) are deduced from spectra to be 3.40/3.58, 3.34/3.55, 3.30/3.50 eV, which are consistent with quantum chemical computational results. The MNi(CO)7- (M = V, Nb, Ta) consists of three bridging carbonyls, one carbonyl terminally bonded to the Ni atom and three carbonyls terminally bonded to the M (M = V, Nb, Ta) atom. These geometries are different from homobinuclear Cr2(CO)7+, Ni2(CO)7+, Pd2(CO)7+, and Fe2(CO)7- and heterobinuclear CuFe(CO)7-, CoZn(CO)7+, and CO is largely activated by a bridging coordination mode. The experimental and theoretical results would provide important information to understand the chemisorbed CO molecules on alloy surfaces or interfaces, which is of great significance to elucidate CO molecule activation processes.

Photoelectron spectroscopy of [Mo6X14]2- dianions (X = Cl-I).

Photoelectron spectroscopy and theoretical investigations have been performed to systematically probe the intrinsic electronic properties of [Mo6X14]2- (X = halogen). All three PE spectra of gaseous [Mo6X14]2- (X = Cl, Br, I) dianions, which were generated by electrospray ionization, exhibit multiple resolved peaks in the recorded binding energy range. Theoretical investigations on the orbital structure and charge distribution were performed to support interpretation of the observed spectra and were further extended onto [Mo6F14]2-, a dianion that was not available for the experimental study. The measured adiabatic (ADE) and vertical detachment energies (VDE) for X = Cl-I were well reproduced by density functional theory calculations (accuracy ∼0.1 eV). Corresponding ADE/VDE values for the dianions were found to be 1.48/2.13 (calc.) and 2.30/2.65, 2.30/2.62, and 2.20/2.42 eV (all expt.) for X = F, Cl, Br, and I, respectively, showing an interesting buckled trend of electron binding energy (EBE) along the halogen series, i.e., EBE (F) ≪ EBE (Cl) ∼ EBE (Br) > EBE (I). Molecular orbital analyses indicate different mixing of metal and halogen atomic orbitals, which is strongly dependent on the nature of X, and suggest that the most loosely bound electrons are detached mainly from the metal core for X = F and Cl, but from halide ligands for X = Br and I. The repulsive Coulomb barrier (RCB), estimated from the photon energy dependent spectra, decreases with increasing halogen size, from 1.8 eV for X = Cl to 1.6 eV for X = I. Electrostatic potential modeling confirms the experimental RCB values and predicts that the most favorable electron detaching pathway should lie via the face-bridging halide ligands.