Anionic States Research Articles

Electric-Field Catalysis on Carbon Nanotubes in Electromicrofluidic Reactors: Monoterpene Cyclizations.

The control over the movement of electrons during chemical reactions with oriented external electric fields (OEEFs) has been predicted to offer a general approach to catalysis. Recently, we suggested that many problems to realize electric-field catalysis in practice under scalable bulk conditions could possibly be solved on multiwalled carbon nanotubes in electromicrofluidic reactors. Here, we selected monoterpene cyclizations to assess the scope of our system in organic synthesis. We report that electric-field catalysis can function by stabilizing both anionic and cationic transition states, depending on the orientation of the applied field. Moreover, electric-field catalysis can promote reactions which are barely accessible by general Brønsted and Lewis acids and field-free anion-π and cation-π interactions, and drive chemoselectivity toward intrinsically disfavored products without the need for pyrene interfacers attached to the substrate to prolong binding to the carbon nanotubes. Finally, interfacing with chiral organocatalysts is explored and evidence against contributions from redox chemistry is provided.

Electric‐Field Catalysis on Carbon Nanotubes in Electromicrofluidic Reactors: Monoterpene Cyclizations

AbstractThe control over the movement of electrons during chemical reactions with oriented external electric fields (OEEFs) has been predicted to offer a general approach to catalysis. Recently, we suggested that many problems to realize electric‐field catalysis in practice under scalable bulk conditions could possibly be solved on multiwalled carbon nanotubes in electromicrofluidic reactors. Here, we selected monoterpene cyclizations to assess the scope of our system in organic synthesis. We report that electric‐field catalysis can function by stabilizing both anionic and cationic transition states, depending on the orientation of the applied field. Moreover, electric‐field catalysis can promote reactions which are barely accessible by general Brønsted and Lewis acids and field‐free anion‐π and cation‐π interactions, and drive chemoselectivity toward intrinsically disfavored products without the need for pyrene interfacers attached to the substrate to prolong binding to the carbon nanotubes. Finally, interfacing with chiral organocatalysts is explored and evidence against contributions from redox chemistry is provided.

Reaction dynamics of the nonvalence bound states of the anions

Nonvalence bound state (NBS) is a unique anionic state where an excess electron is loosely bound to a neutral molecule in long-range potentials. Since Fermi and Teller first proposed that an electron could be bound in the dipolar field of a molecule, the physical and chemical properties of NBS in a variety of chemical systems have been investigated over recent decades. In this short review, recent notable studies aimed at thoroughly understanding the dynamics of NBS in various anionic chemical systems are elaborated. Photodetachment and photoelectron spectroscopic methods, particularly applied to cryogenically cooled anions, have been highly successful in providing detailed rovibronic structures of the NBS in many interesting chemical systems. Furthermore, real-time pump-probe photoelectron spectroscopy unraveled new dynamic aspects of anion physics and chemistry, offering deep insight into mode-specific autodetachment dynamics and the role of metastable NBS as a doorway into anionic chemical reactions. Autodetachment and/or nonvalence-to-valence (or vice versa) electron-transfer dynamics of NBS are found to be strongly mode-specific, presenting a challenge for theoretical explanations of their quantum-mechanical nature. The outlook for further exploration of NBS in various chemical or biological contexts as well as its potential exploitation in controlling chemical reaction is also provided.

Nitrogen‐Nitrogen Bond Breaking in Irradiation Products of Hexanitrohexaazaisowurtzitane (CL‐20)

AbstractWhile the primary result of an interaction of ionizing radiation with an organic material is the ejection of electrons from molecular orbitals producing cations, the free electrons can further interact, yielding excited states; and, potentially, anions. In this work, we computed reaction barriers and energies for N−N bond breaking in the CL‐20 cation, anion, and excited state to investigate if CL‐20 degradation is accelerated after radiation exposure. We focused on N−N bond dissociation because it is the rate‐determining step in the thermal degradation of CL‐20. We found that N−N cleavage rapidly takes place in the CL‐20 cation and anion with greatly reduced reaction energies as compared to CL‐20. We also outlined a potential path for photodissociation of the N−N bond. While CL‐20 is kinetically stable, initial degradation occurs readily in its irradiation products. This is of importance for the performance of the explosive after high‐dose exposure and influences aging if CL‐20 is irradiated at a low dose over extended periods of time.

Machine Learning-Driven Precise Design of Stable OLED Materials: Predicting and Enhancing Multi-State C-N Bond Dissociation Energies

The intrinsic stability of organic light-emitting diode (OLED) materials critically hinges on the bond dissociation energies (BDEs) of fragile bonds, particularly C-N bonds. Despite the necessity of considering BDEs in multiple electronic states due to the complex working conditions of organic materials in OLED devices, comprehensive exploration remains challenging. Herein, we constructed a high-quality dataset, CNBDE-24, comprising nearly 1500 data points for BDEs across multiple electronic states, obtained through an active learning-guided density functional theory (DFT) calculation strategy. Machine learning models trained on the CNBDE-24 dataset exhibit excellent accuracy in predicting BDEs for OLED materials in neutral, triplet excited (T1), and anionic states, achieving an adjusted coefficient of determination exceeding 0.90 on the test set and bypassing the need for high-cost calculation. Moreover, utilizing neutral state BDEs as pre-training data significantly reduces model error and provides deeper insights into the relationships between different BDEs. We find that BDEs in neutral are influenced by the electronic properties of the nitrogen atom, as indicated by descriptors such as Gasteiger charges. Incorporating C-N bonds into aromatic systems and slightly dispersing N atom charges can inherently increase multi-state BDEs without altering luminescent properties. Additionally, anionic BDEs are determined by the extent of charge transfer during bond cleavage and can be regulated by modifying the C-side fragment. High-throughput virtual screening reveals a new stable purple emitter with a dominant 0–0 transition at 360 nm, which was validated through DFT and excited-state property evaluations. Strategies for enhancing BDEs in multiple resonance thermally activated delayed fluorescence materials without altering excited-state properties are also demonstrated.

Why Mg2IrH6 Is Predicted to Be a High‐Temperature Superconductor, But Ca2IrH6 Is Not

The X2MH6 family, consisting of an electropositive cation X and a main group metal M octahedrally coordinated by hydrogen, has been predicted to hold promise for high‐temperature conventional superconductivity. Herein, we analyze the electronic structure of two members of this family, Mg2IrH6 and Ca2IrH6, showing why the former may possess superconducting properties rivaling those of the cuprates, whereas the latter does not. Within Mg2IrH6 the vibrations of the IrH64‐ anions are key for the superconducting mechanism, and they induce coupling in the eg* set, which are antibonding between the H 1s and the Ir dx2−y2 or dz2 orbitals. Because calcium possesses low‐lying d‐orbitals, eg* → Ca d back‐donation is preferred, quenching the superconductivity. Our analysis explains why high critical temperatures were only predicted for second or third row X metal atoms and may hold implications for superconductivity in other systems where the antibonding anionic states are filled.

Why Mg2IrH6 Is Predicted to Be a High-Temperature Superconductor, But Ca2IrH6 Is Not.

The X2MH6 family, consisting of an electropositive cation Xn+ and a main group metal M octahedrally coordinated by hydrogen, have been identified as promising templates for high-temperature conventional superconductivity. Herein, we analyze the electronic structure of two members of this family, Mg2IrH6 and Ca2IrH6, showing why the former may possess superconducting properties rivaling those of the cuprates, whereas the latter does not. Within Mg2IrH6 the vibrations of the anions IrH6 4- anions are key for the superconducting mechanism, and they induce coupling in the set of orbitals, which are antibonding between the H 1s and the Ir or orbitals. Because calcium possesses low-lying d-orbitals, →Ca d back-donation is preferred, quenching the superconductivity. Our analysis explains why high critical temperatures were only predicted for second or third row X metal atoms, and may provide rules for identifying likely high-temperature superconductors in other systems where the antibonding anionic states are filled.

Does Positron Attachment Take Place in Water Solution?

We performed a computational study of positron attachment to hydrated amino acids, namely glycine, alanine, and proline in the zwitterionic form. We combined the sequential quantum mechanics/molecular mechanics (s-QM/MM) method with various levels of any particle molecular orbital (APMO) calculations. Consistent with previous studies, our calculations indicate the formation of energetically stable states for the isolated and microsolvated amino acids, in which the positron localizes around the carboxylate group. However, for the larger clusters, composed of 7 to 40 water molecules, hydrogen bonding between the solute and solvent molecules disfavors positron attachment to the amino acids, giving rise to surface states in which the positron is located around the water-vacuum interface. The analysis of positron binding energies, positronic orbitals, radial probability distributions, and annihilation rates consistently pointed out the change from positron-solute to positron-solvent states. Even with the inclusion of an electrostatic embedding around the aggregates, the positrons did not localize around the solute. Positron attachment to molecules in the gas phase is a well-established fact. The existence of hydrated positronic molecules could also be expected from the analogy with transient anion states, which are believed to participate in radiation damage. Our results indicate that positron attachment to hydrated biomolecules, even to zwitterions with negatively charged carboxylated groups, would not take place. For the larger clusters, in which positron-water interactions are favored, the calculations indicate an unexpectedly large contribution of the core orbitals to the annihilation rates, between 15 and 20%. Finally, we explored correlations between positron binding energies (PBEs) and dipole moments, as well as annihilation rates and PBEs, consistent with previous studies for smaller clusters.

Temporary Anions of Benzoxazole in Charge-Transfer Cluster Photodetachment.

The photoelectron spectra of cluster anions of superoxide (O2-) solvated by one molecule of benzoxazole (BzOx) reveal two competing photodetachment mechanisms: a direct photoemission from the solvated cluster core and an indirect pathway involving temporary anion states of benzoxazole accessed via the O2-·BzOx → O2·BzOx- charge-transfer transitions. Benzoxazole is a bicyclic unsaturated organic molecule that does not form permanent anions. However, its low-lying vacant π* orbitals permit a resonant capture of the electron emitted from the O2- cluster core. The non-Hermitian theory using a complex absorbing potential predicts the existence of two BzOx- π* resonances within the experimental energy range: resonance A (π1*) at 0.891 eV and resonance B (π2*) at 1.76 eV, relative to the onset of the BzOx + e- continuum at the ground-state geometry of neutral BzOx. Within the clusters, the O2·BzOx- charge-transfer states are partially stabilized relative to the free-electron limit by interactions with the O2 molecule. These interactions depend on the electronic states of both species. The theory predicts that at the O2-·BzOx cluster geometry, the O2(X3Σg-)·BzOx-(A) and O2(a1Δg)·BzOx-(A) states lie at 0.56 and 0.47 eV (vertically) above the respective neutral states. The O2(3Σg-)·BzOx-(B) resonance is found 1.43 eV (vertically) above O2(X3Σg-)·BzOx. Intense signatures of both BzOx- resonances and the three above-mentioned charge-transfer cluster states, O2(X3Σg-)·BzOx-(A), O2(a1Δg)·BzOx-(A), and O2(3Σg-)·BzOx-(B) are observed in the 355 nm (3.495 eV) and 532 nm (2.330 eV) photoelectron spectra of the O2-·BzOx cluster anion.

Stable Meisenheimer Complexes as Powerful Photoreductants Readily Obtained from Aza-Hetero Aromatic Compounds.

Excited states of radical anions derived from the photoreduction of stable organic molecules are suggested to serve as potent reductants. However, excited states of these species are too short-lived to allow bimolecular quenching processes. Recently, the singlet excited state of Meisenheimer complexes, which possess a long-lived excited state, was identified as the competent species for the reduction of challenging organic substrates (-2.63 V vs. SCE, saturated calomel electrode). To produce reasonably stable and simply accessible different Meisenheimer complexes, the addition of nBuLi to readily available aromatic heterocycles was investigated, and the photoreactivity of the generated species was studied. In this paper, we present the straightforward preparation of a family of powerful photoreductants (*Eox<-3 V vs. SCE in their excited states, determined by DFT and time-dependent TD-DFT calculations; DFT, density functional theory) that can induce dehalogenation of electron-rich aryl chlorides and to form C-C bond through radical cyclization. Photophysical analyses and computational studies in combination with experimental mechanistic investigations demonstrate the ability of the adduct to act as a strong electron donor under visible light irradiation.

Stable Meisenheimer Complexes as Powerful Photoreductants Readily Obtained from Aza‐Hetero Aromatic Compounds

AbstractExcited states of radical anions derived from the photoreduction of stable organic molecules are suggested to serve as potent reductants. However, excited states of these species are too short‐lived to allow bimolecular quenching processes. Recently, the singlet excited state of Meisenheimer complexes, which possess a long‐lived excited state, was identified as the competent species for the reduction of challenging organic substrates (−2.63 V vs. SCE, saturated calomel electrode). To produce reasonably stable and simply accessible different Meisenheimer complexes, the addition of nBuLi to readily available aromatic heterocycles was investigated, and the photoreactivity of the generated species was studied. In this paper, we present the straightforward preparation of a family of powerful photoreductants (*Eox&lt;−3 V vs. SCE in their excited states, determined by DFT and time‐dependent TD‐DFT calculations; DFT, density functional theory) that can induce dehalogenation of electron‐rich aryl chlorides and to form C−C bond through radical cyclization. Photophysical analyses and computational studies in combination with experimental mechanistic investigations demonstrate the ability of the adduct to act as a strong electron donor under visible light irradiation.

Advancing Our Understanding of the Excited States of the Tantalum Anion.

Our study provides a comprehensive theoretical examination of the energy levels associated with the neutral tantalum atom and its ions in various charge states (Ta, Ta+, and Ta-), employing the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, and relativistic infinite order two-component (IOTC) method with multiconfiguration complete active space self-consistent field (CASSCF) followed by the second-order single-state multireference perturbation (CASPT2) methods. The effect of spin-orbit (SO) coupling is introduced via the restricted active space state interaction (RASSI) method, utilizing atomic mean field SO integrals (AMFI). Through IOTC CASSCF/CASPT2 RASSI calculations, we determined the electron affinity (EA) of the tantalum atom to be 0.321 eV, which stands among the most accurate theoretical values achieved to date. This result closely aligns with the experimental measurement of 0.329 eV. Our investigation highlights potential discrepancies between the predicted symmetry of the excited states of the tantalum anion and experimental observations. Additionally, we calculated the bonding energies for transitions from Ta- to Ta and identified four potential bound or quasi-bound states in the tantalum anion.

Methyl Methacrylate Copolymer with Pendant Thioxanthenone Groups as Active Layer for Resistive Memory Devices.

An electro-active copolymer of methyl methacrylate and 2-((4-acroylpiperazine-1-yl)methyl)-9H-thioxanthene-9-one (poly(MMA-co-ThS)) was synthesized by radical polymerization. The copolymer has good solubility in most organic solvents, thermal stability up to 282 °C and excellent ability to form thin films on silicon wafers. Poly(MMA-co-ThS) films exhibited an electrochemical and electrochromic activity resulting in the formation of long-lived radical anion states of pendant thioxanthone groups inside the film. These states exhibit optical transitions in the visible region as a broad optical absorption band, 500<λ<900 nm (1.38<Wopt(ThS)<2.48 eV) with a maximum at λmax=675 nm (1.84 eV). Using temperature measurements of the current-voltage characteristics of p-Si(100)/poly(MMA-co-ThS)/Al devices, it was shown that the charge transport in the film occurs by a multiphonon mechanism, which is quantitatively described by the Nasyrov-Gritsenko model of phonon-assisted tunneling between traps. The value of the optical transition energy of the trap, determined by the Nasyrov-Gritsenko model, Wopt=1.8 eV, is in a good agreement with Wopt(ThS), confirming the nature of the traps as 9H-thioxanthen-9-one structures. The n++Si(100)/poly(MMA-co-ThS)/Al memory device exhibited a memristive effect (reversible ON/OFF switching of the device) with an initial "forming" cycle followed by repetitive memory cycles characterized by bipolar switching.

Determination of the Electronic Structure, Charge-transfer, and Optical Properties of Neutral, Anionic, and Cationic Perfluoropentacene

Perfluoropentacene ( is an n-type organic semiconductor made by fluorination of p-type semiconductor Pentacene and can find applications in molecular thin film devices. In this work, a theoretical study of Perfluoropentacene was carried out based on density functional theory (DFT) and time dependent (TD-DFT) as implemented in Gaussian 09 package using B3LYP/6-311++G (d, p) and B3LYP/6-31+G(d) basis sets. The electronic, charge transfer, Linear and nonlinear optical properties of the molecule were calculated and reported for the neutral, anionic, and cationic forms of the molecule. The results show that the cationic state of the molecule has the strongest bond length at R(28,32) using the basis sets B3LYP/6-311++G (d,p) and the weakest bond length was found at R(4,6) in the ionic state with 6-31+G (d) basis set. The energy gap obtained for the neutral molecule using 6-31+G (d) and 6-311++G (d,p) basis sets are 2.00eV, 1.99eV respectively. The results show a strong agreement with a previously related work that reported the energy gap as 2.02eV thus indicating high stability of the molecule. Perfluoropentacene has the highest value of chemical hardness of 1.3929eV in its anionic state (Beta MO), so is considered to be harder and more stable than the neutral and cationic. The findings also revealed that with toluene as solvent, the strongest absorption was found at wavelength of 738.38, highest oscillator strength of 0.0599 and the lowest excitation energy of 1.6791eV. The calculated results of polarizability, first and second hyperpolarizability confirm that this molecule is a good non-linear optical material. On the whole, the molecule could be a good material for optoelectronic applications.

Toward a numerically efficient description of bulk-solvated anionic states.

We investigate the vertical electron attachment energy (VAE) of 1-methyl-4-nitroimidazole, a model radiosensitizer, employing quantum mechanics/molecular mechanics (QM/MM) and QM/polarized continuum (QM/PCM) solvation models. We considered the solvent-excluded surface (QM/PCM-SES) and Van der Waals (QM/PCM-VDW) cavities within the PCM framework, the electrostatic embedding QM/MM (EE-QM/MM) model, and the self-consistent sequential QM/MM polarizable electrostatic embedding (scPEE-S-QM/MM) model. Due to slow VAE convergence concerning the number of QM solvent molecules, full QM calculations prove inefficient. Ensemble averages in these calculations do not align with VAEs computed for the representative solute-solvent configuration. QM/MM and QM/PCM calculations show agreement with each other for sufficiently large QM regions, although the QM/PCM-VDW model exhibits artifacts linked to the cavity. QM/MM models demonstrate good agreement between ensemble averages and VAEs calculated with the representative configuration. Notably, the VAE computed with the scPEE-S-QM/MM model achieves faster convergence concerning the number of QM water molecules compared to the EE-QM/MM model, attributed to enhanced efficiency from MM charge polarization in the scPEE-S-QM/MM approach. This emphasizes the importance of QM/classical models with accurate solute-solvent and solvent-solvent mutual polarization for obtaining converged VAEs at a reasonable computational cost. The full-QM approach is very inefficient, while the microsolvation model is inaccurate. Computational savings in QM/MM models result from electrostatic embedding and the representative configuration, with the scPEE-S-QM/MM approach emerging as an efficient tool for describing bulk-solvated anions within the QM/MM framework. Its potential extends to improving transient anion state descriptions in biomolecules and radiosensitizers, especially given the frequent employment of microsolvation models.

Effect of N Atom Substitution on Electronic Resonances: A 2D Photoelectron Spectroscopic and Computational Study of Anthracene, Acridine, and Phenazine Anions.

The accommodation of an excess electron by polycyclic aromatic hydrocarbons (PAHs) has important chemical and technological implications ranging from molecular electronics to charge balance in interstellar molecular clouds. Here, we use two-dimensional photoelectron spectroscopy and equation-of-motion coupled-cluster calculations of the radical anions of acridine (C13H9N-) and phenazine (C12H8N2-) and compare our results for these species to those for the anthracene anion (C14H10-). The calculations predict the observed resonances and additionally find low-energy two-particle-one-hole states, which are not immediately apparent in the spectra, and offer a slightly revised interpretation of the resonances in anthracene. The study of acridine and phenazine allows us to understand how N atom substitution affects electron accommodation. While the electron affinity associated with the ground state anion undergoes a sizable increase with the successive substitution of N atoms, the two lowest energy excited anion states are not affected significantly by the substitution. The net result is that there is an increase in the energy gap between the two lowest energy resonances and the bound ground electronic state of the radical anion from anthracene to acridine to phenazine. Based on an energy gap law for the rate of internal conversion, this increased gap makes ground state formation progressively less likely, as evidenced by the photoelectron spectra.

Spectroscopy and dynamics of isolated anions: Versatile instrumentation for photodetachment and photoelectron spectroscopy.

Molecular anions are appealing targets for study because, compared with their neutral and cationic counterparts, they can be probed with conventional laboratory lasers without the need for multiphoton ionization schemes, and they provide spectroscopic details on the corresponding neutral molecules. Here, we describe a section of a modular instrument designed to perform high-throughput photoelectron and photodetachment spectroscopy of gas-phase anions, with future provision for time-resolved and isomer-selective spectroscopy. The instrument framework allows for the incorporation and adaptation of several ion sources, as demonstrated here with plasma (electric) discharge sources providing variable hard to soft ion generation conditions. The generated anions are separated according to their mass-to-charge ratio through time-of-flight mass spectrometry (m/zΔm/z = 500-600) and are focused into a set of perpendicular velocity-map imaging electrodes (ΔEE≈4%), where mass-selected anions are probed using laser light and the ejected electrons are velocity-map imaged. Instrument performance is demonstrated through the acquisition of photodetachment and photoelectron spectra for CH2CN-, showing sharp resonances in the vicinity of the detachment threshold assigned to rovibrational states of a dipole-bound anion and broader lifetime-limited spectral features at photon energies well above the threshold assigned to prompt autodetachment from a temporary anion resonance. Similar measurements could be performed on any molecular anions generated in the sources.

Demonstrating the Connection between the Nonvalence Correlation-Bound Anions of Polyaromatic Hydrocarbons and the Image Potential States of Graphene Using a One-Electron Model Hamiltonian.

The ground and excited state nonvalence correlation-bound (NVCB) anion states of the hexagonal polycylic aromatic hydrocarbons and of hexagonal graphene nanoflakes are characterized using a one-electron model Hamiltonian which incorporates atomic electrostatic moments up to the quadrupole, coupled inducible charges and dipoles, and atom-centered Gaussians to describe the short-range repulsive interactions. Extrapolation of the calculated electron binding energies of the lowest energy symmetric and antisymmetric (with respect to the molecular plane) NVCB anions of both the polycylic aromatic hydrocarbons and the carbon nanoflakes to the n → ∞ limit yields binding energies that are in good agreement with those of the most stable symmetric and antisymmetric image potential states of freestanding graphene as determined from two-photon photoemission spectroscopy (2PPE) experiments.

Physical analysis of aspirin in different phases and states using density functional theory

This study analyzed the aspirin molecule (C9H8O4) using Density Functional Theory (DFT) on Gaussian 09W software. First, the structure of aspirin was optimized using the DFT method with the B3LYP functional and the 6-311+G (d,p) basis set. A global reactivity study was employed to understand the reactivity of aspirin in gas and solvent water for both anion and neutral states. To understand the involvement of orbitals in chemical stability and electron conductivity, we calculated the HOMO-LUMO. The thermodynamic function of a molecule was understood using thermochemistry. Molecular Electrostatic Potential (MEP) was employed to understand the physiochemical properties of aspirin. We observed the Mulliken atomic charge to calculate the atomic charge of aspirin. Finally, the title molecule's UV–Vis, FTIR, and Raman spectra are analyzed and compared with the experimental data.

Novel Approach for Predicting Vertical Electron Attachment Energies in Bulk-Solvated Molecules.

When low-energy electrons interact with molecules, they can give rise to transient anion states commonly known as resonances. These states are formed through vertical electron attachment processes and have the potential to induce various forms of DNA lesions, including base damage, single- and double-strand breaks, cross-links, and clustered lesions that are challenging to repair. So far, most experimental and theoretical studies have investigated the formation of resonances of (bio)molecules in the gas phase or in microsolvated environments. Since cellular environments are mainly composed of water molecules, it is crucial to understand how bulk water affects the resonances of (bio)molecules. Given the existing gap in studies on resonances of bulk-solvated molecules, we propose a novel theoretical-computational approach to address this void. Our approach combines the multibasis-set (time-dependent-)density functional theory and self-consistent sequential quantum mechanics/molecular mechanics polarizable electrostatic embedding methods. We apply this combined methodology to predict the vertical electron attachment energies of 1-methyl-5-nitroimidazole (1M5NI), a well-known radiosensitizer model, in bulk water. In addition, we analyze the rapid mutual polarization between the resonances (both shape- and core-excited) of 1M5NI and the surrounding bulk water environment. For comparison, we also studied the isolated and microsolvated 1M5NI. Overall, while the polarization of the environment is clearly sensitive to the solute charge, causing a significant impact on the vertical electron affinity and consequently on the attachment electron energies, it does not have a significant impact on the excitation energies of the anion.