Molecular Anions Research Articles

Collision excitation of c-C3H-(X1A1) by He.

Accurate modeling of anionic abundances in the interstellar and circumstellar media requires calculations of collisional data with the most abundant species that are usually He atoms and H2 molecules. In this paper, we focus on smaller cyclic molecular anion, c-C3H-, an astrophysical candidate, following the detection of larger CnH- carbon chains. From a new three-dimensional potential energy surface, the rotational (de-)excitation of the c-C3H-(X1A1) anion by collision with He is investigated. The surface is obtained in the supermolecular approach at the CCSD(T)-F12/aug-cc-pVTZ level of theory. Fully quantum close-coupling calculations of inelastic integral cross sections are performed on a grid of collisional energies large enough to ensure the convergence of the state-to-state rate coefficients for the 34 first rotational levels up to jKa,Kc = 77,0 of c-C3H- and temperatures ranging from 5 to 100K. For this collisional system, rate coefficients exhibit a strong dominance in favor of 21,2 → l1,1 downward transition. This transition was previously used for the detection of the cyclic parent c-C3H. The c-C3H--He rate coefficients (∼10-11cm3s-1) are of the same order of magnitude as those of the detected anions CnH- (as C2H-, C4H-, and C6H-) in collision with He and one order of magnitude smaller than those with H2. The critical densities of H2 were also estimated, and a discussion on the validity of the local thermodynamic equilibrium conditions is carried out. This work represents the contribution to understanding and modeling abundances and chemistry of hydrocarbon radicals, CnH, in astrophysical media.

Preparation, QTAIM and Single‐Crystal Exploration of the Pyrimethamine‐Based Co‐Crystal Salts with Substituted Benzoic Acids

AbstractThe effective preparation of pyrimethamine based co‐crystal salts with substituted benzoic acids (4‐nitrobenzoic acid 1 and 5‐chlorosalicylic acid 2) in methanol has been reported. The crystal structure of salt 1 and 2 is acquired through the x‐rays diffraction technique. Hirshfeld surface analysis elaborates the comparative study of the non‐covalent interactions in salt 1 and 2. In order to theoretically evaluate the non‐covalent interactions between molecular ions in salts 1 and 2, DFT and TD‐DFT calculations of molecular salts were performed. FMO and GRD analyses were performed to evaluate the reactivity of molecular ions. While, NBO, AIM and NCI analyses were performed to explore the non‐covalent interactions between cation and anions of molecular salts 1 and 2. The calculations demonstrated that salt 1 has H‐bond slightly stronger than salt 2 due to the withdrawing effect of ‐NO2 substituent group. The molecular anions reactivity allows different patterns of non‐covalent interactions that affect the salts arrangement in the crystal.

A Computer Simulation Study of Thermal and Mechanical Properties of Poly(Ionic Liquid)s.

Thermal and mechanical properties of poly(ionic liquid)s (PILs), an epoxidized ionic liquid-amine network, are studied via molecular dynamics simulations. The poly(ionic liquid)s are designed with two different ionic liquid monomers, 3-[2-(Oxiran-2-yl)ethyl]-1-{4-[(2-oxiran-2-yl)ethoxy]phenyl}imidazolium (EIM2) and 1-{4-[2-(Oxiran-2-yl)ethyl]phenyl}-3-{4-[2-(oxiran-2-yl)ethoxy]benzyl}imidazolium (EIM1), each of which is networked with tris(2-aminoethyl)amine, paired with different anions, bis(trifluoromethanesulfonyl)imide (TFSI−) and chloride (Cl−). We investigate how ionic liquid monomers with high ionic strength affect structures of the cross-linked polymer networks and their thermomechanical properties such as glass transition temperature (Tg) and elastic moduli, varying the degree of cross-linking. Strong electrostatic interactions between the cationic polymer backbone and anions build up their strong structures of which the strength depends on their molecular structures and anion size. As the anion size decreases from TFSI− to Cl−, both Tg and elastic moduli of the PIL increase due to stronger electrostatic interactions present between their ionic moieties, making it favorable for the PIL to organize with stronger bindings. Compared to the EIM2 monomer, the EIM1 monomers and TFSI− ions generate a PIL with higher Tg and elastic moduli. This attributes to the less flexible structure of the EIM1 monomer for the chain rotation, in which steric hindrance by ring moieties in the EIM1-based PIL enhances their structural rigidity. The - stacking structures between the rings are found to increase in EIM1-based PIL compared to the EIM2-based one, which becomes stronger with smaller Cl− ion rather than TFSI−. The effect of the degree of the cross-linking on thermal and mechanical properties is also examined. As the degree of cross-linking decreases from 100% to 60%, Tg also decreases by a factor of 10–20%, where the difference among the given PILs becomes decreased with a lower degree of cross-linking. Both the Young’s (E) and shear (G) moduli of all the PILs decrease with degree of cross-linking, which the reduction is more significant for the PIL generated with EIM2 monomers. Transport properties of anions in PILs are also studied. Anions are almost immobilized globally with very small structural fluctuations, in which Cl− presents lower diffusivity by a factor of ~2 compared to TFSI− due to their stronger binding to the cationic polymer backbone.

Bisphosphonates on Smooth TiO2: Modeling and Characterization

AbstractThis paper presents insights into surfaces properties of sputter‐deposited titania modified with bisphosphonates, including zeta potential measurements in a pH range. Functionalization was investigated through simulation and experimental approaches to model the adsorbate and evaluate structure‐response relationships. Molecules of etidronic, alendronic, and risedronic acids were investigated through density functional theory. The molecules vary their reactivity through similar structures considering different scenarios. X‐ray photoelectron spectroscopy of titania/BP systems demonstrated that functionalization occurs in a short time and resulted in a predominantly “side‐on” adsorbate configuration after two hours of immersion. Zeta potential showed the predominancy of negative charges deprotonated free phosphonates. Water contact angle demonstrated that titania surfaces are hydrophilic after overnight functionalization. Atomic force measurements of bisphosphonates layers suggested that the molecular anions follow the surface topography, unchanging the surface roughness.

Non covalent bonds in some bromo-substituted aromatic anions

Four bromo-substituted derivatives of naphthalene and anthracene were studied by means of Dissociative Electron Attachment Spectroscopy. Long-lived molecular anions with lifetimes ranging from 25 to 144 μs were observed in all molecules under investigation. In all cases molecular anion fragmentation is poor: only the Brˉ, [M-Br]ˉ and (with very small intensity) [M-H]ˉ species were observed, except for the case of 9,10-Br2-anthracene. It was shown that the presence of long-lived molecular anions in 1-Br- and 2-Br-naphthalene (τa=26 μs and τa=25 μs, respectively) does not contradict the fact that their dissociation rates measured by the pulse radiolysis method are fairly large (1.0 ×1010 s−1 and 1.8 ×1010 s−1, respectively). Scanning the potential energy surface of anions in the process of positioning a bromine anion around a polarized aromatic radical revealed the presence of a series of local minima separated by potential barriers. It is inferred that the most energetically favorable structures of the 1-Br- and 2-Br-naphthalene anions should be interpreted as complexes of the bromide anion bound to the polarized aromatic radical by non-covalent Br--H bonds. Similar local minima were found in the 9-Br- and 9,10-Br2-anthracene anions, but the energies of these structures are significantly higher than those of the “standard” anionic structures with a C-Br bond length of ~1.93 Å. The EAas obtained with DFT CAM-B3LYP/6–311 +G(d,p) calculations are in acceptable agreement with the estimates made within the framework of the simple Arrhenius model from the lifetimes of molecular anions.

HF Formation through Dissociative Electron Attachment-A Combined Experimental and Theoretical Study on Pentafluorothiophenol and 2-Fluorothiophenol.

In chemoradiation therapy, dissociative electron attachment (DEA) may play an important role with respect to the efficiency of the radiosensitizers used. The rational tailoring of such radiosensitizers to be more susceptive to DEA may thus offer a path to increase their efficiency. Potentially, this may be achieved by tailoring rearrangement reactions into the DEA process such that these may proceed at low incident electron energies, where DEA is most effective. Favorably altering the orbital structure of the respective molecules through substitution is another path that may be taken to promote dissociation up on electron capture. Here we present a combined experimental and theoretical study on DEA in relation to pentafluorothiophenol (PFTP) and 2-fluorothiophenol (2-FTP). We investigate the thermochemistry and dynamics of neutral HF formation through DEA as means to lower the threshold for dissociation up on electron capture to these compounds, and we explore the influence of perfluorination on their orbital structure. Fragment ion yield curves are presented, and the thermochemical thresholds for the respective DEA processes are computed as well as the minimum energy paths for HF formation up on electron capture and the underlying orbital structure of the respective molecular anions. We show that perfluorination of the aromatic ring in these compounds plays an important role in enabling HF formation by further lowering the threshold for this process and through favorable influence on the orbital structure, such that DEA is promoted. We argue that this approach may offer a path for tailoring new and efficient radiosensitizers.

Total Electron Detachment and Induced Cationic Fragmentation Cross Sections for Superoxide Anion (O2-) Collisions with Benzene (C6H6) Molecules.

In this study, novel experimental total electron detachment cross sections for O2− collisions with benzene molecules are reported for the impact energy range (10–1000 eV), as measured with a transmission beam apparatus. By analysing the positively charged species produced during the collision events, relative total ionisation cross sections were derived in the incident energy range of 160–900 eV. Relative partial ionisation cross sections for fragments with m/z ≤ 78 u were also given in this energy range. We also confirmed that heavier compounds (m/z > 78 u) formed for impact energies between 550 and 800 eV. In order to further our knowledge about the collision dynamics governing the fragmentation of such heavier molecular compounds, we performed molecular dynamics calculations within the framework of the Density Functional Theory (DFT). These results demonstrated that the fragmentation of these heavier compounds strongly supports the experimental evidence of m/z = 39–42, 50, 60 (u) cations formation, which contributed to the broad local maximum in the total ionisation observed from 550 to 800 eV. This work reveals the reactivity induced by molecular anions colliding with hydrocarbons at high energies, processes that can take place in the interstellar medium under various local conditions.

Micellar shuttle of a polymeric ionic liquid (P(EHO)-CI-P(EtOx)) in a water/ethyl acetate two-phase system: Micellar load capacity and selective transfer of molecular anions

Selective ionic load behaviour of a polymeric ionic liquid (PIL) (poly(3-ethyl-3-hydroxymethyloxetane)-cationic-imidazolium-poly(2-ethyl-2-oxazoline) and molecular transfer in a biphasic system (water/ethyl acetate) are investigated using dissipative particle dynamics (DPD) simulations and coarse-grained models. The mesoscopic simulations show that the PIL generates stable spherical micelles in an aqueous environment at room temperature and has the selective characteristic (via a cationic-imidazolium mesh in the micellar core) to separate anionic molecules of a mixture of organic dyes (methyl orange and methyl violet). At high temperatures (≥low critical solution temperature (≈333 K)), the PIL micelles lose their thermodynamic stability via a cloud point, and the gradual insolubility of the PIL micelles in the aqueous environment promotes micellar shuttles towards the organic phase where the polymeric micellar corona is regenerated. All the transitory stages involving the selective ionic load process and maximum load capacity during micellar shuttle formation in the biphasic system are analysed in detail. Our theoretical results are in good agreement with the experimental ones. The study is expected to contribute to the understanding of the relationship between selective ionic transfer and micellar shuttle in biphasic systems under the effect of temperature.

From Cc to P63mc: Structural Variation in La3S2Cl2[SbS3] and La3OSCl2[SbS3] Induced by the Isovalent Anion Substitution

The first antimony oxychloride sulfide, namely, La3OSCl2[SbS3], has been designed by isovalent anion substitution strategy. It belongs to the polar hexagonal space group P63mc (No. 186) with a = 9.327(5) Å, c = 7.075(5) Å, V = 533.0(5) Å3, and Z = 2. It is composed of three-dimensional (3D) cationic [La3OSCl2]3+ networks hosting covalent [SbS3] molecular anions. The 3D cationic [La3OSCl2]3+ are formed by the one-dimensional (1D) hexagonal columns of corner-shared [(Cl/S)La3] polyhedra propagating along the 63 axis situated in (0,0,z) and [OLa3] trigonal pyramids via corner-sharing. Moreover, the alternating [SbS3] and [OLa3] trigonal pyramids are arranged along the 3-fold axis located at (1/3, 2/3, z), generating a dipole moment component along the c-direction. Another remarkable structural motif is the occurrence of the empty octahedra formed by the disordered Cl/S anions, which further share the face to form 1D chains extending along the 63 axis located at (0,0,z). Interestingly, the occurrence of the isolated [La3SbOS3]4+ cubane-like clusters instead of the “chains of [La3SbOS3]4+” make the title compound distinct from the related La4OCl2S4 featuring common chains of [La4OS3]4+. The preliminary nonlinear optical (NLO) measurement indicates a moderate second-harmonic-generation (SHG) signal (ca. 0.7 × AgGaS2) at 2050 nm laser. Moreover, calculated birefringence for La3OSCl2[SbS3] is ∼0.269 at 2050 nm. In addition, the optical energy gap of 2.5 eV for La3OSCl2[SbS3] was derived, which can be assigned to the charge transition from the highest value of valence band derived dominantly from the of S 3p states to the lowest value of conduction band mainly made up of the Sb 5p and of La 5d states.

Preparation of tricationic tris(pyridylpalladium(ii)) metallacyclophane as an anion receptor

A tricationic tris(pyridylpalladium(II)) metallacyclophane was prepared from 3,5-dibromopyridine by a successive treatment with tetrakis(triphenylphosphine)palladium(0), diphosphine, and silver salt. Single-crystal X-ray diffraction analysis revealed that the metallacyclophane incorporated one of three counter anions into its hole-shaped cavity to form multidentate C-H⋯anion interactions. Solution-phase 1H NMR experiments in DMSO-d6 indicated that the metallacyclophane exhibited selective binding behavior toward nitrate, tetrafluoroborate, p-toluenesulfonate, perchlorate, and hydrogen sulfate ions, whereas the hexafluoroantimonate ion exhibited only weak interaction toward the metallacyclophane. This anion recognition behavior was further demonstrated by an extraction experiment of water-soluble sulfonate dyes.

Binding of saturated and unsaturated C6-hydrocarbons to the electrophilic anion [B12Br11]-: a systematic mechanistic study.

The highly reactive gaseous ion [B12Br11]- is a metal-free closed-shell anion which spontaneously forms covalent bonds with hydrocarbon molecules, including alkanes. Herein, we systematically investigate the reaction mechanism for binding of [B12Br11]- to the five hexane isomers yielding [B12Br11(C6H14)]-, as well as to cyclohexane and several hexene isomers (yielding [B12Br11(C6H12)]-) using collision-induced dissociation (CID), infrared photodissociation spectroscopy (IRPD) and computational methods. CID of the different [B12Br11(C6H14)]- ions results in distinct fragmentation patterns dependent on the structure of the hexane isomer. The observed fragmentation reactions provide insights into the addition mechanism of [B12Br11]- to hexane. Based on the observed CID patterns, we identified that either B-C bond formation through heterolytic C-C or C-H bond cleavages or B-H bond formation through heterolytic C-H cleavage occur dependent on the structure of the hexane isomer. Meanwhile, we observe identical CID spectra of adducts originating from isomers of C6H12. Spectroscopic investigations of adducts of 1-hexene and cyclohexane indicate the same product structure with an open C6 chain. Computational investigations evidenced that low lying transition states are present, which enable a ring opening reaction of cyclohexane when binding to [B12Br11]-.

Photostability of the deprotonated forms of the UV filters homosalate and octyl salicylate: molecular dissociation versus electron detachment following UV excitation.

While common molecular anions show a strong propensity to undergo electron detachment upon UV excitation, this process often occurs in competition with molecular ion dissociation. The factors that affect the balance between these two major possible decay pathways have not been well understood to date. Laser photodissociation spectroscopy of the deprotonated forms of the UV filter molecules, Homosalate (HS) and Octyl Salicylate (OS), i.e. [HS − H]− and [OS − H]−, was used to acquire gas-phase UV absorption spectra for [HS − H]− and [OS − H]−via photodepletion from 3.0–5.8 eV. No photofragmentation (i.e. dissociation of the ionic molecular framework) was observed for either [HS − H]− and [OS − H]− following photoexcitation, revealing that electron loss entirely dominates the electronic decay pathways for these systems. High-level quantum chemical calculations were used to map out the excited states associated with [HS − H]− and [OS − H]−, revealing that the minimum-energy crossing points (MECPs) between the S1 and S0 states are located in elevated regions of the potential energy surface, making internal conversion unlikely. These results are consistent with our experimental observation that electron detachment out-competes hot ground state molecular fragmentation. More generally, our results reveal that the competition between molecular dissociation and electron detachment following anion photoexcitation can be determined by the magnitude of the energy gap between the excitation energy and the MECPs, rather than being a simple function of whether the excitation energy lies above the anion's vertical detachment energy.

Probing vibronic coupling of a transiently charged state of a single molecule through subnanometer resolved electroluminescence imaging

The intramolecular vibronic coupling has a great effect on molecular electronic transitions and associated spectral characteristics, which is a central topic in the study of molecular spectroscopy. In this paper, we investigate the vibronic coupling of a transiently charged state within a single 3,4,9,10-perylenetetracarboxylicdianhydride (PTCDA) molecule in real space by imaging the spatial distribution of single-molecule electroluminescence via highly localized excitation of tunneling electrons in a plasmonic nanocavity. The electron injections from a scanning tunneling microscope tip into a PTCDA molecule on a silver-supported ultrathin salt layer produce a transient doubly charged molecular anion that emits vibrationally resolved fluorescence. The sub-molecular resolved spectroscopic imaging for the –2 valence transiently charged state shows a two-spot pattern along the molecular short axis for the purely electronic 0-0 transition. However, the observed two-spot orientation for certain anti-symmetric vibronic-state imaging is found to be evidently different from the purely electronic 0-0 transition, rotating 90°, which reflects the change in the transition dipole orientation from along the molecular short axis to the long axis. Such a change directly reveals the occurrence of strong vibronic coupling associated with a large Herzberg-Teller (HT) contribution, which goes beyond the conventional Franck-Condon (FC) picture. Combined with theoretical calculations, the anti-symmetric vibration is found to have a strong dynamic disturbance to the transition density of purely electronic transitions, especially those atoms with large transition densities, which induces a strong transition charge oscillation along the long axis of the molecule and thus leads to a transition dipole along the long axis of the molecule. On the other hand, for vibronic emissions associated with the totally symmetric molecular vibration (such as the v<sub>1</sub> (A<sub>g</sub>) mode described above), the observed two-spot orientation in the vibronic-state imaging pattern is found to be the same as the purely electronic 0-0 transition, which directly reveals its FC-dominated nature. Notably, the vibration-induced emission associated with HT-dominated contributions (such as the v<sub>2</sub> (B<sub>3g</sub>) mode) is often discussed in the literature by using an intensity borrowing mechanism via the state mixing with other high-lying eigenstates. In the present work, the v<sub>2</sub>-vibration with B<sub>3g</sub> symmetry is likely to modulate the zero-order electronic wavefunction of the S<sub>1</sub> state in a way to best resemble that of the S<sub>2</sub> state (<i>i.e.</i>, induce efficient mixing of the electronic excited state S<sub>1</sub> with the electronic excited state S<sub>2</sub>), so that the v<sub>2</sub>-vibration induced emission seems to borrow intensities from neighboring S<sub>2</sub>→S<sub>0</sub> transitions. Our results provide a new route for the real-space understanding of the microscopic picture for the vibronic coupling within a single molecule in a transiently charged state.

Nonadiabatic Dynamics between Valence, Nonvalence, and Continuum Electronic States in a Heteropolycyclic Aromatic Hydrocarbon.

Internal conversion between valence-localized and dipole-bound states is thought to be a ubiquitous process in polar molecular anions, yet there is limited direct evidence. Here, photodetachment action spectroscopy and time-resolved photoelectron imaging with a heteropolycyclic aromatic hydrocarbon (hetero-PAH) anion, deprotonated 1-pyrenol, is used to demonstrate a subpicosecond (τ1 = 160 ± 20 fs) valence to dipole-bound state internal conversion following excitation of the origin transition of the first valence-localized excited state. The internal conversion dynamics are evident in the photoelectron spectra and in the photoelectron angular distributions (β2 values) as the electronic character of the excited state population changes from valence to nonvalence. The dipole-bound state subsequently decays through mode-specific vibrational autodetachment with a lifetime τ2 = 11 ± 2 ps. These internal conversion and autodetachment dynamics are likely common in molecular anions but difficult to fingerprint due to the transient existence of the dipole-bound state. Potential implications of the present excited state dynamics for interstellar hetero-PAH anion formation are discussed.

Soluble Complexes of Cobalt Oxide Fragments Bring the Unique CO2 Photoreduction Activity of a Bulk Material into the Flexible Domain of Molecular Science.

The deposition of metal oxides is essential to the fabrication of numerous multicomponent solid-state devices and catalysts. However, the reproducible formation of homogeneous metal oxide films or of nanoparticle dispersions at solid interfaces remains an ongoing challenge. Here we report that molecular hexaniobate cluster anion complexes of structurally and electronically distinct fragments of cubic-spinel and monoclinic Co3O4 can serve as tractable yet well-defined functional analogues of bulk cobalt oxide. Notably, the energies of the highest-occupied and lowest-unoccupied molecular orbitals (HOMO and LUMO) of the molecular complexes, 1, closely match the valence- and conduction-band (VB and CB) energies of the parent bulk oxides. Use of 1 as a molecular analogue of the parent oxides is demonstrated by its remarkably simple deployment as a cocatalyst for direct Z-scheme reduction of CO2 by solar light and water. Namely, evaporation of an aqueous solution of 1 on TiO2-coated fluorinated tin oxide windows (TiO2/FTO), immersion in wet acetonitrile, and irradiation by simulated solar light under an atmosphere of CO2 give H2, CO, and CH4 in ratios nearly identical to those obtained using 20 nm spinel-Co3O4 nanocrystals, but 15 times more rapidly on a Co basis and more rapidly overall than other reported systems. Detailed investigation of the photocatalytic properties of 1 on TiO2/FTO includes confirmation of a direct Z-scheme charge-carrier migration pathway by in situ irradiated X-ray photoelectron spectroscopy. More generally, the findings point to a potentially important new role for coordination chemistry that bridges the conceptual divide between molecular and solid-state science.

Observation of the ponderomotive effect in non-valence bound states of polyatomic molecular anions

The ponderomotive force on molecular systems has rarely been observed hitherto, despite potentially being extremely useful for the manipulation of the molecular properties. Here, the ponderomotive effect in the non-valence bound states has been experimentally demonstrated, for the first time to the best of our knowledge, giving great promise for the manipulation of polyatomic molecules by the dynamic Stark effect. Entire quantum levels of the dipole-bound state (DBS) and quadrupole-bound state (QBS) of the phenoxide (or 4-bromophenoxide) and 4-cyanophenoxide anions, respectively, show clear-cut ponderomotive blue-shifts in the presence of the spatiotemporally overlapped non-resonant picosecond control laser pulse. The quasi-free electron in the QBS is found to be more vulnerable to the external oscillating electromagnetic field compared to that in the DBS, suggesting that the non-valence orbital of the former is more diffusive and thus more polarizable compared to that of the latter.

Matrix-assisted production of actinide molecular anions for AMS

The multiple probable oxidation states of actinide elements can lead to their molecular anions to result in complicated yield patterns from a Cs+ sputter ion source. For actinides AMS, two methods can be practiced in order to concentrate the yields into just one or two anion species. The present common practice has been to avoid excessive oxygen reactions in the sputter targets, so that the mono-oxide anions can be produced with good or applicable ionization efficiencies. However, this method requires the typical 860-type Cs+ sputter ion sources to be operated with relatively high Cs+ fluxes, a condition that not all such sources in use can be operated with lasting stability. On the contrary, with low Cs+ fluxes, good or applicable ionization efficiencies can also be achieved for producing element-specific polyatomic oxide, oxyfluoride, or fluoride anions of actinides, if the sputter targets are aided with dominantly oxidizing or fluorinating matrices. This paper describes a systematic study of such phenomena using ZnO and FeF3 to form the respective oxidizing and fluorinating matrices. It was found that using the chosen set of polyatomic fluoride anions and the FeOxHy + FeF3 sputter targets, not only all rare actinides could be measured with low backgrounds matching those using mono-oxides, but also with the available ionization efficiencies fully utilized within a shorter time. A few additional merits are also noted.

Layered Double Hydroxides as a Drug Delivery Vehicle for S-Allyl-Mercapto-Cysteine (SAMC)

The intercalations of anionic molecules and drugs in layered double hydroxides (LDHs) have been intensively investigated in recent years. Due to their properties, such as versatility in chemical composition, good biocompatibility, high density and protection of loaded drugs, LDHs seem very promising nanosized systems for drug delivery. In this work, we report the intercalation of S-allyl-mercapto-cysteine (SAMC), which is a component of garlic that is well-known for its anti-tumor properties, inside ZnAl-LDH (hereafter LDH) nanostructured crystals. In order to investigate the efficacy of the intercalation and drug delivery of SAMC, the intercalated compounds were characterized using X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The increase in the interlayer distance of LDH from 8.9 Å, typical of the nitrate phase, to 13.9 Å indicated the intercalation of SAMC, which was also confirmed using FT-IR spectra. Indeed, compared to that of the pristine LDH precursor, the spectrum of LDH-SAMC was richly structured in the fingerprint region below 1300 cm−1, whose peaks corresponded to those of the functional groups in the SAMC molecular anion. The LDH-SAMC empirical formula, obtained from UV-Vis spectrophotometry and thermogravimetric analysis, was [Zn0.67Al0.33(OH)2]SAMC0.15(NO3)0.18·0.6H2O. The morphology of the sample was investigated using SEM: LDH-SAMC exhibited a more irregular size and shape of the flake-like crystals in comparison with the pristine LDH, with a reduction in the average crystallite size from 3 µm to about 2 µm. In vitro drug release studies were performed in a phosphate buffer solution at pH 7.2 and 37 °C and were analyzed using UV-Vis spectrophotometry. The SAMC release from LDH-SAMC was initially characterized by a burst effect in the first four hours, during which, 32% of the SAMC is released. Subsequently, the release percentage increased at a slower rate until 42% after 48 h; then it stabilized at 43% and remained constant for the remaining period of the investigation. The LDH-SAMC complex that was developed in this study showed the improved efficacy of the action of SAMC in reducing the invasive capacity of a human hepatoma cell line.

Ab Initio Simulations of Poorly and Well Equilibrated (CH3CN)n- Cluster Anions: Assigning Experimental Photoelectron Peaks to Surface-Bound Electrons and Solvated Monomer and Dimer Anions.

Excess electrons in liquid acetonitrile are of particular interest because they exist in two different forms in equilibrium: they can be present as traditional solvated electrons in a cavity, and they can form some type of solvated molecular anion. Studies of small acetonitrile cluster anions in the gas phase show two isomers with distinct vertical detachment energies, and it is tempting to presume that the two gas-phase cluster anion isomers are precursors of the two excess electron species present in bulk solution. In this paper, we perform DFT-based ab initio molecular dynamics simulations of acetonitrile cluster anions to understand the electronic species that are present and why they have different binding energies. Using a long-range-corrected density functional that was optimally tuned to describe acetonitrile cluster anion structures, we have theoretically explored the chemistry of (CH3CN)n- cluster anions with sizes n = 5, 7, and 10. Because the temperature of the experimental cluster anions is not known, we performed two sets of simulations that investigated how the way in which the cluster anions are prepared affects the excess electron binding motif: one set of simulations simply attached excess electrons to neutral (CH3CN)n clusters, providing little opportunity for the clusters to relax in the presence of the excess electron, while the other set allowed the cluster anions to thermally equilibrate near room temperature. We find that both sets of simulations show three distinct electron binding motifs: electrons can attach to the surface of the cluster (dipole-bound) or be present either as solvated monomer anions, CH3CN-, or as solvated molecular dimer anions, (CH3CN)2-. All three species have higher binding energies at larger cluster sizes. Thermal equilibration strongly favors the formation of the valence-bound molecular anions relative to surface-bound excess electrons, and the dimer anion becomes more stable than the monomer anion and surface-bound species as the cluster size increases. The calculated photoelectron spectra from our simulations in which there was poor thermal equilibration are in good agreement with experiment, suggesting assignment of the two experimental cluster anion isomers as the surface-bound electron and the solvated molecular dimer anion. The simulations also suggest that the shoulder seen experimentally on the low-energy isomer's detachment peak is not part of a vibronic progression but instead results from molecular monomer anions. Nowhere in the size range that we explore do we see evidence for a nonvalence, cavity-bound interior-solvated electron, indicating that this species is likely only accessible at larger sizes with good thermal equilibration.

Alkylimidazolium Ionic Liquids Absorption and Diffusion in Wood

Ionic liquids represent a class of highly tunable organic compounds responsible for many applications in the domain of wood-based materials. It has often been emphasized that the use of ionic liquids derives from their high affinity for lignocellulose and their good penetration ability into wood structures. This paper discusses the sorption ability of different types of 1-alkyl-3-methylimidazolium ionic liquids with lateral alkyl chains, ranging from ethyl to hexyl into spruce and beech wood, as a function of their cation molecular mass, anion type (chloride, tetrafluoroborate, acetate), and intrinsic properties (surface tension and kinematic viscosity) at room temperature. All the studied ionic liquids present high relative uptake values at the equilibrium, ranging from 11.2% to 69.7%. The bulk diffusion coefficients of the ionic liquids into the wood range from 2 × 10−3 to 28 × 10−3 mm2/min, being higher in the longitudinal direction for both types of wood. The value of the diffusion coefficients for 1-ethyl-3-methylimidazolium chloride is only 25% lower than that for water, despite the obvious differences in viscosity and surface tension, demonstrating a good penetration ability and the potential for wood industry-related applications (as impregnation compound carriers and preservatives).