33 Search Results

Tellurocyanate, [TeCN]⁻, is the heaviest group 16 congener of the cyanate anion, [OCN]⁻. Due to the relative instability of the C─Te bond, tellurocyanate chemistry has seen only scarce attention. Here, we present the facile synthesis and thorough characterization of [K@crypt-222][TeCN]. The anion is essentially linear with interatomic distances C─N = 1.150(6)Å and C─Te = 2.051(4)Å, thus approximating a C≡N triple bond and for C─Te a bond order between 1 and 2. Fully ¹³C and ¹⁵N labeled [Te¹³C¹⁵N]⁻ allowed for the extraction of chemical shifts and all possible coupling constants (¹³C = 77.8 ppm, ¹⁵N = 285.7 ppm, ¹²⁵Te = −566more » ppm, ¹J_13C-15N = 8 Hz, ¹J_13C-125Te = 748 Hz, ²J1_5N-125Te = 55 Hz), which were also determined independently by quantum chemical calculations. In the series [ChCN]⁻ (Ch = O─Te), [TeCN]⁻ shows the strongest spin-orbit coupling (SOC) induced heavy-atom effect on the light-atom shielding (SO-HALA-effect). In contrast, ¹⁵N shifts are also well described without considering relativistic effects and/or SOC. Negative-ion photoelectron spectroscopy was used to extract the electron affinity (EA = 3.034 eV) and spin-orbit splitting (3807 cm⁻¹) of [TeCN]^•. These values continue the trends of falling EA and rising SOC in the series [ChCN]^•.« less

Electrolyte anions are pivotal for lithium battery performance, yet their fundamental electronic structural properties are not well understood. In this work, we employ a combination of negative-ion photoelectron spectroscopy (NIPES), ab initio calculations, and molecular dynamics (MD) simulations to investigate the electronic structures of three representative electrolyte anions. This multiscale approach enables us to elucidate how their intrinsic electronic properties govern anion–solvent interactions in gas-phase clusters, as well as lithium-ion (Li⁺) solvation structures and ion transport behavior in the condensed phase. NIPES reveals that difluoro(oxalato)borate (DFOB^–), bis(fluorosulfonyl)imide (FSI^–), and bis(oxalato)borate (BOB^–) all exhibit high electron binding energies, with vertical/adiabatic detachmentmore » energies increasing from DFOB^– (6.09/5.70 eV) to FSI^– (6.80/6.10 eV) to BOB^– (6.82/6.40 eV), correlating with enhanced oxidation stability. Ab initio calculations reveal that DFOB^–/FSI^––solvent complexes bind Li⁺ ∼ 10 kcal/mol stronger than BOB^– series, aligning with the strength of a Li⁺–anion model. DFOB^– exhibits pronounced charge localization on both oxygen and fluorine atoms, enabling their involvement in Li⁺ coordination. In contrast, fluorine atoms in FSI^– are largely electron-depleted and remain excluded from direct Li⁺ binding. MD simulations further demonstrate that LiDFOB and LiFSI systems exhibit Li⁺ diffusion coefficients three and five times higher than those of LiBOB across four common solvents. Notably, LiFSI salt in acetonitrile (AN) exhibits the fastest Li⁺ diffusion among 12 electrolyte systems, highlighting the synergistic effect of FSI^– and AN in promoting ion mobility. In conclusion, these findings provide a molecular-level understanding of the critical roles of anion and its microsolvation in optimizing Li⁺ diffusion dynamics, once again emphasizing the positioning of FSI^– and DFOB^– as prime candidates for next-generation electrolytes.« less

Ion triplets of the chloride salts of two commonly used weakly coordinating cations are reported (i.e., Cl^–·NMe₄⁺Cl^– (1^–) and Cl^–·PPh₄⁺Cl^– (2^–)). Negative ion photoelectron spectra at 20 K afford vertical and adiabatic detachment energies of 5.18 and 5.00 eV (1^–) and 5.03 and 4.70 eV (2^–), respectively. These results are well reproduced by coupled cluster calculations with single, double, and perturbative triple excitations (CCSD(T)) whereas M06-2X is systematically too small by ~0.3 eV (i.e., 7 kcal mol^–1). The structures of both 1^– and 2^– have five or six C–H···Cl^– interactions that stabilize these cluster anions by 32 (1^–) and 27more » (2^–) kcal mol^–1 as given by their chloride dissociation enthalpies. In conclusion, these values drop to 7.4 and 3.8 kcal mol^–1 in dichloromethane based up conductor-like polarizable continuum model calculations and suggest that X^–·M⁺X^– ion triplets with a weakly coordinating cation maybe the reactive form of salts under some conditions.« less

Due to their unique physiochemical properties that may be tailored for specific purposes, ionic liquids (ILs) have been investigated for various applications, including chemical separations, catalysis, energy storage, and space propulsion. The different cations and anions comprising ILs may be selected to optimize a range of desired properties, such as thermal stability, ionic conductivity, and volatility, leading to the designation of certain ILs as designer “green” solvents. The effect of counterions on the properties of ILs is of both fundamental scientific interest and technological importance. Herein, we report a systematic experimental and theoretical investigation of the size, charge, stability towardmore » dissociation, and geometric/electronic structure of 1-ethyl-3-methyl imidazolium (EMIM)-based IL clusters containing two different atomic counterions (i.e., bromide [Br⁻] and iodide [I⁻]). This work extends our studies of EMIM⁺ cations with atomic chloride (Cl⁻) and molecular tetrafluoroborate (BF₄⁻) anions reported previously by Baxter et al. [Chem. Mater. 34, 2612 (2022)] and Zhang et al. [J. Phys. Chem. Lett. 11, 6844 (2020)], respectively. Distributions of anionic IL clusters were generated in the gas phase using electrospray ionization and characterized by high mass resolution mass spectrometry, energy-resolved collision-induced dissociation, and negative ion photoelectron spectroscopy experiments. The experimental results reveal anion-dependent trends in the size distribution, relative abundance, ionic charge state, stability toward dissociation, and electron binding energies of the IL clusters. Complementary global optimization theory provides molecular-level insights into the bonding and electronic structure of a selected subset of clusters, including their low energy structures and electrostatic potential maps, and how these fundamental characteristics are influenced by anion substitution. Collectively, our findings demonstrate how the fundamental properties of ILs, which determine their suitability for many applications, may be tuned by substituting counterions. These observations are critical in the sub-nanometer cluster size regime where phenomena do not scale predictably to the bulk phase, and each atom counts toward determining behavior.« less

Here, we report a joint spectroscopic and theoretical study probing spin-orbit coupling (SOC) in a variety of molecular complexes between an iodine atom and a ligand (L) with L ranging from Ar, HF to formic/acetic acids, and glycine/N-methylated glycine derivatives. Cryogenic photoelectron spectroscopy of L·I^- (L=HCOOH, CH₃COOH) reveals three distinct peaks, identified as three SOC states, denoted as X(1/2), A(3/2), and B(l/2) for the corresponding neutrals. The X and A separation ΔE_XA is measured to be 0.10 eV for both, whereas the X and B gap ΔE_XB is 0.98 and 0.97 eV for formic and acetic acid, respectively. These newmore » ΔE_XA values are compared with the previously reported values for the molecular complexes L·I· with L=Ar, HF, glycine, and A-methylated glycines. All together these complexes encompass a diversity of intermolecular interactions, from van der Waals to weak and strong hydrogen bonding. While the ΔE_XB remains similar, the ΔE_XA is shown to be extremely sensitive to the type of ligands and interactions, spanning from 5 meV to 150 meV. High-level relativistic quantum calculations including explicit SOC formulism nicely reproduce all experimental SOC splitting. A direct correlation between the magnitude of ΔE_XA with the intermolecular interaction strength or bond distance of the neutral complexes—the stronger interaction (shorter bond length), the greater splitting, is established.« less

Microhydrated closo-Boranes have attracted great interests due to their superchaotropic activity related to well-known Hofmeister effect and important applications in biomedical and battery fields. In this work, we report a combined negative ion photoelectron spectroscopy and quantum chemical investigation on hydrated closo-decaborate clusters [B₁₀H₁₀]^2-·nH₂O (n = 1 – 7) with a direct comparison to their analogues [B₁₂H₁₂]^2-·nH₂O and free water clusters. A single H₂O molecule is found sufficient to stabilize the intrinsically unstable [B₁₀H₁₀]^2- dianion. The first two water molecules strongly interact with the solute forming B-H···H-O dihydrogen bonds while additional water molecules show substantially reduced binding energies. Unlike [B₁₂H₁₂]^2-·nH₂Omore » possessing highly structured water network with the attached H₂O molecules arranged in a unified pattern by maximizing B-H···H-O dihydrogen bonding, distinct structural arrangements of the water clusters within [B₁₀H₁₀]^2–·nH₂O are achieved with the water cluster networks from trimer to heptamer resembling free water clusters. Such a distinct difference arises from the variations in size, symmetry, and charge distributions between these two dianions. Finally, the present finding again confirms the structural diversity of hydrogen-bonding networks in microhydrated closo-boranes and enrich our understanding of aqueous borate chemistry.« less

Conducting a comprehensive molecular-level evaluation of a photoacid generator (PAG) and its subsequent impact on lithography performance can facilitate the rational design of a promising 193 nm photoresist tailored to specific requirements. In this study, we integrated spectroscopy and computational techniques to meticulously investigate the pivotal factors of three prototypical PAG anions, p-toluenesulfonate (pTS^-), 2-(trifluoromethyl)benzene-1-sulfonate (TFMBS^-), and triflate (TF^-), in the lithography process. Our findings reveal a significant redshift in the absorption spectra caused by specific PAG anions, attributed to their involvement in electronic transition processes, thereby enhancing the transparency of the standard PAG cation, triphenylsulfonium (TPS⁺), particularly at ~193 nm. Furthermore,more » the electronic stability of PAG anions can be enhanced by solvent effects with varying degrees of strength. Here we observed the lowest vertical detachment energy of 6.6 eV of pTS^- in PGMEA solution based on the polarizable continuum model, which prevents anion loss at 193 nm lithography. In addition, our findings indicate gas-phase proton affinity values of 316.4 kcal/mol for pTS^-, 308.1 kcal/mol for TFMBS^-, and 303.2 kcal/mol for TF^-, which suggest the increasing acidity strength, yet even the weakest acid pTS^- is still stronger than strong acid HBr. The photolysis of TPS⁺-based PAG, TPS⁺·pTS^-, generated an excited state leading to homolysis bond cleavage with the lowest reaction energy of 83 kcal/mol. Overall, the PAG anion pTS^- displayed moderate acidity, possessed the lowest photolysis reaction energy, and demonstrated an appropriate redshift. These properties collectively render it a promising candidate for an effective acid producer.« less

Although the intrinsic electronic properties of polyoxometalates (POMs) can be greatly influenced by modifying them with organic substituents, their resistive switching behavior on surfaces dependent on the organic substituents remains largely unexplored. In this work, we assessed the importance of electron-withdrawing and electron-donating ligand substituents on the material properties of a series of hybrid Lindqvist-type hexavanadates TBA₂[V₆O₁₃((OCH₂)₃CCH₂OH)₂] (TBA₂V₆-OH), TBA₂[V₆O₁₃((OCH₂)₃CMe)₂] (TBA₂V₆-Me), TBA₂[V₆O₁₃((OCH₂)₃CNHCOCH₂Cl)₂] (TBA₂V₆-Cl), and TBA₂[V₆O₁₃((OCH₂)₃CNHCOCH₂-OOCC₁₀H₁₅)₂] (TBA₂V₆-Ad) as potential resistive random-access memory (ReRAM) components. Compared to their redox behavior in solution, changing the ligand substituents on surfaces results in no significant effect on the potential and, thus, no effect on the resistancemore » steps in the current-voltage profiles. However, while the current-voltage characteristics do not change, the peripheral metal-free substituents in the trisalkoxide framework of Lindqvist-type hexavanadate molecules influence the adsorption and switching stability of these POMs on gold. This work highlights the noticeable differences between hexavanadate's redox properties in solution (which follow the trend observed in the gas phase) and hexavanadate's resistive switching properties on conducting surfaces. Importantly, their multi-state switching behavior is not significantly altered by the different type of substituent at the periphery of the trisalkoxo ligands.« less

Despite being an important closo-borate in the condensed phase boron chemistry, isolated B₁₀H₁₀^2- is electronically unstable and has never been detected in the gas phase. Herein, we report a successful capture of this fleeting species through binding with an octamethylcalix[4]pyrrole (omC4P) molecule to form a stable gaseous omC4P·[B₁₀H₁₀]^2- complex and its characterizations utilizing negative ion photoelectron spectroscopy (NIPES). The recorded NIPE spectrum, contributed from both omC4P and [B₁₀H₁₀]^2-, is deconvoluted by subtracting the omC4P contribution to yield a [B₁₀H₁₀]^2- spectrum. The obtained [B₁₀H₁₀]^2- spectrum consists of four major bands spanning electron binding energy (EBE) range from 1 to 5 eVmore » with the EBE gaps matching excellently with the energy intervals of computed highly lying occupied molecular orbitals of the B₁₀H₁₀^2- dianion. Finally, this study showcases a generic method to utilize omC4P to capture unstable multiply charged anions in the gas phase for experimental determination of their electronic structures.« less

Abstract The harpoon mechanism has been a milestone in molecular reaction dynamics. Until now, the entity from which electron harpooning occurs has been either alkali metal atoms or non‐metallic analogs in their excited states. In this work, we demonstrate that a common organic molecule, octamethylcalix[4] pyrrole (omC4P), behaves just like alkali metal atoms, enabling the formation of charge‐separated ionic bonding complexes with halogens omC4P ⁺  ⋅  X ⁻ ( X =F−I, SCN) via the harpoon mechanism. Their electronic structures and chemical bonding were determined by cryogenic photoelectron spectroscopy of the corresponding anions and confirmed by theoretical analyses. The omC4P ⁺more »  ⋅  X ⁻ could be visualized to form from the reactants omC4P+ X via electron harpooning from omC4P to X at a distance defined by the energy difference between the ionization potential of omC4P and electron affinity of X .« less