Vertical Attachment Energies Research Articles

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.

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.

Astro-electrochemistry of NH3 clusters and ice: e− trapping, stability, and electron transfer

ABSTRACT Quantifying electron trapping and transfer to small molecules is crucial for interfacial chemistry. In an astrochemical context, we study how NH3 clusters in both crystalline and amorphous forms can capture low-energy electrons to form ammoniated electrons. Electron affinities, vertical detachment energies, and vertical attachment energies were computed via ab initio static and dynamics simulations, (DFT, DLPNO-CCSD(T);AIMD), for (NH3)n clusters (n = 4, 5, 6, 8, 14, 23, and 38). Our results indicate that the clusters could trap and stabilize the unpaired electron which is always externally localized on the clusters. Interactions of the ammoniated electron clusters with astrochemically relevant molecules indicate that electron transfer to water and methanol are feasible, forming the radical anions (H2O)−· and (CH3OH)−·. The trapping of electrons by both crystalline and amorphous NH3 ices, and subsequent transfer to small molecules, highlights ‘astro-electrochemical’ reactions, and has implications for both astrochemistry as well as terrestrial cluster science.

Dissociative properties of C4F6 obtained using computational chemistry

The electronic properties of C4F6 were investigated by using computational chemistry to clarify the dissociative channels in the process plasma. The results show the mainly ionized ion is C3F3 + (CF2=C=CF+; propargyl ion) which is observed in the mass spectrum with the electron energy of 70 eV, and the intermediate molecular structure to produce C3F3 + ion is methyl allene ion (CF2=C=CF–CF3 +). The molecular ion C4F6 + is also mainly produced in the ionization threshold region. For the excited states, the calculated results suggest that CF2CFCF + CF2 dissociation takes place in the energy region higher than 7.0 eV and C2F3 + C2F3 dissociation takes place in the energy region higher than 8.0 eV. In the electron attachment process, the vertical electron attachment energy was calculated as 1.1 eV and the nonadiabatic negative ion energy was −0.2 eV lower than the energy of neutral C4F6.

Potential of HF and CO2 loss through dissociative electron attachment to increase radiosensitizers reactivity; case study on pentafluorobenzoic acid

Radiosensitizers reactions with low energy electrons, generated within malignant tissue in radiotherapy, may play a significant role in the efficacy of chemoradiotherapy. Specifically, in situ dissociative electron attachment to such radiosensitizers may cause effective frag-mentation and the formation of reactive species that, in turn, may cause DNA damage and cell death. In the current study we explore the potential of sensitizing molecular systems towards DEA, using the model compound pentafluoro benzoic acid. Dissociative electron attachment is studied experimentally and quantum chemical calculations are used to determine the threshold energies for the observed processes and to explore the vertical attachment energies and underlying orbital structures. We find that perfluorination significantly alters the fragmentation pattern of benzoic acid and enables efficient HF and CO2 loss at very low attachment energies, leading to the formation of the complementary radical and closed shell anions. The efficiency of these processes is discussed in context to the respective thermochemistry and orbital structure and in the context of the potential of fluorination as means to tailor effective radiosensitizers.

Ground and Electronically Excited States of Main-Group-Metal-Doped B20 Double Rings.

Ab initio coupled-cluster, electron propagator, and Møller-Plesset second-order perturbation theory calculations are utilized to analyze the low-lying electronic states of several metal-doped B20. In the ground state, the presently focused AB20/EB20 (A = Li, Na, and K; E = Mg and Ca) consist of charge-separated A+B20-/E2+B202- frameworks. The excited electronic states of AB20 and EB20+ were analyzed by computing the vertical electron attachment energies (VEAEs) of AB20+ and EB202+. In several excited states, the radical electron is predominantly localized on the B20 frames, which are counterparts of the low-lying states of bare B20-. A variety of basis sets were tested on obtaining VEAEs, and the aug-cc-pVDZ/A,E d-aug-cc-pVDZ/B combination provided the best accuracy-efficiency compromise on them. Furthermore, this work analyzes the Rydberg-like excited states of AB20 and EB20+ and will serve as a guide for future studies on similar metal-doped boron systems.

Electron binding energies and Dyson orbitals of OnH2n+1 +,0,- clusters: Double Rydberg anions, Rydberg radicals, and micro-solvated hydronium cations.

Ab initio electron propagator methods are employed to predict the vertical electron attachment energies (VEAEs) of OH3 +(H2O)n clusters. The VEAEs decrease with increasing n, and the corresponding Dyson orbitals are diffused over exterior, non-hydrogen bonded protons. Clusters formed from OH3 - double Rydberg anions (DRAs) and stabilized by hydrogen bonding or electrostatic interactions between ions and polar molecules are studied through calculations on OH3 -(H2O)n complexes and are compared with more stable H-(H2O)n+1 isomers. Remarkable changes in the geometry of the anionic hydronium-water clusters with respect to their cationic counterparts occur. Rydberg electrons in the uncharged and anionic clusters are held near the exterior protons of the water network. For all values of n, the anion-water complex H-(H2O)n+1 is always the most stable, with large vertical electron detachment energies (VEDEs). OH3 -(H2O)n DRA isomers have well separated VEDEs and may be visible in anion photoelectron spectra. Corresponding Dyson orbitals occupy regions beyond the peripheral O-H bonds and differ significantly from those obtained for the VEAEs of the cations.

Effective Fragment Potentials for Flexible Molecules: Transferability of Parameters and Amino Acid Database.

An accurate but efficient description of noncovalent interactions is a key to predictive modeling of biological and materials systems. The effective fragment potential (EFP) is an ab initio-based force field that provides a physically meaningful decomposition of noncovalent interactions of a molecular system into Coulomb, polarization, dispersion, and exchange-repulsion components. An EFP simulation protocol consists of two steps, preparing parameters for molecular fragments by a series of ab initio calculations on each individual fragment, and calculation of interaction energy and properties of a total molecular system based on the prepared parameters. As the fragment parameters (distributed multipoles, polarizabilities, localized wave function, etc.) depend on a fragment geometry, straightforward application of the EFP method requires recomputing parameters of each fragment if its geometry changes, for example, during thermal fluctuations of a molecular system. Thus, recomputing fragment parameters can easily become both computational and human bottlenecks and lead to a loss of efficiency of a simulation protocol. An alternative approach, in which fragment parameters are adjusted to different fragment geometries, referred to as "flexible EFP", is explored here. The parameter adjustment is based on translations and rotations of local coordinate frames associated with fragment atoms. The protocol is validated on extensive benchmark of amino acid dimers extracted from molecular dynamics snapshots of a cryptochrome protein. A parameter database for standard amino acids is developed to automate flexible EFP simulations in proteins. To demonstrate applicability of flexible EFP in large-scale protein simulations, binding energies and vertical electron ionization and electron attachment energies of a lumiflavin chromophore of the cryptochrome protein are computed. The results obtained with flexible EFP are in a close agreement with the standard EFP procedure but provide a significant reduction in computational cost.

Elastic-electron-scattering from 1,2-ethylenediamine and dimethyldiazene

We present elastic integral, differential and momentum transfer cross sections for scattering of electrons by 1,2-ethylenediamine (NH2C2H4NH2) and by dimethyldiazene (CH3N2CH3). The cross sections were computed with the Schwinger multichannel method implemented with norm-conserving pseudopotentials. The calculations were carried out in the static-exchange and static-exchange plus polarization approximations for energies up to 20 eV. We found the presence of a Ramsauer–Townsend minimum at around 0.38 eV in the integral cross section of 1,2-ethylenediamide and a π* shape resonance at around 1.0 eV in the integral cross section of dimethyldiazene, both cross sections computed in the static-exchange plus polarization approximation. In the static-exchange approximation the resonance is located at 3.5 eV. For dimethyldiazene we also employed an empirical scaling relation to estimate the vertical attachment energy and the value of 1.1 eV agree well with the position of the resonance of 1.0 eV obtained through the scattering calculation. We compare our results with recent calculations [G. L. C. de Souza, J. Electron Spectrosc. Relat. Phenom. 234, 64 (2019)] and found in general a very good agreement in the shape of the cross sections, but there are some discrepancies regarding their magnitude.

Solvent effects on the π* shape resonances of uracil

We have investigated the effect of microsolvation on the π* shape resonances of uracil, referred to as π1 * and π2 * in the order of increasing energy. Our study considered uracil-water aggregates with six solvent molecules obtained from Monte Carlo simulations in the liquid phase. To explore the ensemble statistics, we combined scattering calculations, performed in the static exchange and static exchange plus polarization approximations, with linear regressions of virtual orbital energies to the scattering results. In general, the solvent molecules stabilize the anion states, and the lower lying π1 * resonance becomes a bound state in most of the solute-water clusters. We also discuss how the strength of the H bonds can affect the energies of the anion states, in addition to the number and donor/acceptor characters of those bonds. The thermal distributions for the vertical attachment energies, obtained from 133 statistically uncorrelated solute-solvent clusters, are significantly broad in the energy scale of the autoionization widths. The distributions for the π1 * and π2 * anion states slightly overlap, thus giving rise to a quasi-continuum of attachment energies below ≲2.5 eV, in contrast to the gas phase picture of electron attachment to well separated resonances below the electronic excitation threshold. Both the stabilization of the anion states and the spread of attachment energies could be expected to favor the dissociative electron attachment processes believed to underlie the electron-induced damage to biomolecules.

Ionized water clusters , n = 2 to 6: A high‐accuracy study of structures and energetics

AbstractIonized water clusters, , have been of remarkable interest owing to their crucial roles in many chemical and biological processes. Small cationic water clusters , n = 2 to 6 serve as reasonable models for understanding the nature of the ionized water. In this study, employing high‐level ab initio quantum chemical methods, such as the density‐fitted orbital‐optimized linearized coupled‐cluster doubles (DF‐OLCCD), coupled‐cluster singles and doubles (CCSD), and coupled‐cluster singles and doubles with perturbative triples [CCSD(T)], a high‐accuracy study of structures and energetics for cationic water clusters [, n = 2‐6] is presented. In this study, 2 dimer, 8 trimer, 18 tetramer, 23 pentamer, and 25 hexamer clusters are reported. Most of the structures considered are reported for the first time. Relative, binding, and vertical attachment energies (VAEs), for the first time, are presented at the complete basis set (CBS) limit, extrapolating energies of the aug‐cc‐pVTZ and aug‐cc‐pVQZ basis sets, to provide the most accurate energetics to date. Our results demonstrate that as cluster size increases, the VAE value decreases, which indicates that large‐size clusters better compensate for the electron deficiency compared with small‐size clusters. The VAE values for pentamer and hexamer clusters are 118.5 to 165.5 and 121.9 to 153.7 kcal mol−1, respectively. Further, our binding energy results, at the CCSD(T)/CBS level, indicate strong bindings in cationic clusters due to hydrogen bond interactions. The average binding energy per water molecule varies from −16.6 to −21.8 kcal mol−1 for the clusters considered. Hence, we present the most extensive and accurate study on ionized water clusters to date. Further, our results indicate that the DF‐OLCCD method is very promising for ionic molecular clusters, and its accuracy approaches the CCSD(T) quality. The inexpensive analytic gradients of DF‐OLCCD, compared with CCSD(T), make it very helpful for high‐accuracy studies of molecular geometries.

Energetics of CO2- in Aqueous Solution.

Gas-phase and aqueous solution properties of neutral and anionic clusters of CO2 with 3, 4, and 8 explicit H2O molecules are calculated at the coupled cluster (CCSD(T)) level plus a self-consistent reaction field. Anionic clusters with the radical electron density localized on the carbon of the CO2 molecule rather than localized on the H2O molecules are more favorable energetically by 10-20 kcal/mol in the gas phase (Δ Hgas(298 K)) and 20-30 kcal/mol in aqueous solution (Δ Gaq(298 K)). The most favorable structures are those with the largest number of strong hydrogen bonds between the CO2- and the explicit H2O molecules. Adiabatic electron affinities were calculated in the gas phase and in aqueous solution for the microsolvated anion. The adiabatic electron affinity of aqueous CO2- is predicted to be 2.35 ± 0.08 eV and is converged with as few as 3 explicit H2O molecules plus a self-consistent reaction field. The EA of aqueous CO2 is significantly greater than the aqueous solvation free energy of the electron. The vertical attachment energies to CO2 and the vertical detachment energies from CO2- were calculated. The solvated CO2- anion is substantially bent to 135°, which requires 1.52 eV. The large energy required for bending in combination with the vertical detachment and attachment energies shows that substantial local solvent reorganization occurs on detachment or attachment of an electron to solvated CO2. The formation of aqueous C2O42- from CO2- was also explored, and dimerization is predicted to occur.

Low-energy electron collisions with proline and pyrrolidine: A comparative study.

We present a comparative study on the calculated cross sections obtained for the elastic collisions of low-energy electrons with the amino acid proline (C5H9NO2) and its building block pyrrolidine (C4H9N). We employed the Schwinger multichannel method implemented with pseudopotentials to compute integral, differential, and momentum transfer cross sections in the static-exchange plus polarization approximation, for energies up to 15 eV. We report three shape resonances for proline at around 1.7 eV, 6.8 eV, and 10 eV and two shape resonances for pyrrolidine centered at 7 eV and 10.2 eV. The present resonance energies are compared with available experimental data on vertical attachment energies and dissociative electron attachment, where a good agreement is found. From the comparison of the present results with available calculated cross sections for the simplest carboxylic acid, formic acid (HCOOH), and from electronic structure calculations, we found that the first resonance of proline, at 1.7 eV, is due the presence of the carboxylic group, whereas the other two structures, at 6.8 eV and 10 eV, clearly arise from the pyrrolidine ring. A comparison between the differential cross sections for proline and pyrrolidine at some selected energies of the incident electron is also reported in this paper.

Non-iterative triple excitations in equation-of-motion coupled-cluster theory for electron attachment with applications to bound and temporary anions.

The impact of residual electron correlation beyond the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) approximation on positions and widths of electronic resonances is investigated. To establish a method that accomplishes this task in an economical manner, several approaches proposed for the approximate treatment of triple excitations are reviewed with respect to their performance in the electron attachment (EA) variant of EOM-CC theory. The recently introduced EOM-CCSD(T)(a)* method [D. A. Matthews and J. F. Stanton, J. Chem. Phys. 145, 124102 (2016)], which includes non-iterative corrections to the reference and the target states, reliably reproduces vertical attachment energies from EOM-EA-CC calculations with single, double, and full triple excitations in contrast to schemes in which non-iterative corrections are applied only to the target states. Applications of EOM-EA-CCSD(T)(a)* augmented by a complex absorbing potential (CAP) to several temporary anions illustrate that shape resonances are well described by EOM-EA-CCSD, but that residual electron correlation often makes a non-negligible impact on their positions and widths. The positions of Feshbach resonances, on the other hand, are significantly improved when going from CAP-EOM-EA-CCSD to CAP-EOM-EA-CCSD(T)(a)*, but the correct energetic order of the relevant electronic states is still not achieved.

Frontier molecular orbitals of a single molecule adsorbed on thin insulating films supported by a metal substrate: electron and hole attachment energies

We present calculations of vertical electron and hole attachment energies to the frontier orbitals of a pentacene molecule absorbed on multi-layer sodium chloride films supported by a copper substrate using a simplified density functional theory (DFT) method. The adsorbate and the film are treated fully within DFT, whereas the metal is treated implicitly by a perfect conductor model. We find that the computed energy gap between the highest and lowest unoccupied molecular orbitals—HOMO and LUMO -from the vertical attachment energies increases with the thickness of the insulating film, in agreement with experiments. This increase of the gap can be rationalised in a simple dielectric model with parameters determined from DFT calculations and is found to be dominated by the image interaction with the metal. We find, however, that this simplified model overestimates the downward shift of the energy gap in the limit of an infinitely thick film.

Transient negative ion spectrum of the cytosine-guanine pair

We employed elastic scattering calculations, performed in the static exchange approximation, to investigate the π ∗ transient anion states of cytosine, guanine and the cytosine-guanine pair. Our results for the isolated monomers, also obtained in the static-exchange plus polarization approximation, are in good agreement with the available calculations and electron transmission data. Virtual orbital analysis for the lower-lying π ∗ anion states, with pure shape resonance character, indicates that electron attachment to the cytosine-guanine pair gives rise to resonances located on either monomer (the orbitals do not delocalize over the pair). The π ∗ shape resonances of the pair localized on the cytosine unit have lower energies in comparison with those of the isolated base, with the opposite trend for the guanine unit. The underlying mechanism would be the net positive charge transfer to the cytosine unit, as the guanine monomer acts as a proton donor in two out of the three hydrogen bonds formed in the pair. Even though the calculations were performed in the static-exchange approximation (due to the size of the system), the conclusions drawn were also corroborated by empirical estimates of the vertical attachment energies. The results for the cytosine-guanine pair are compared to those previously obtained for the formic acid-formamide complex, having two hydrogen bonds with opposite donor/acceptor characters and negligible charge transfer.

Ion Mobility Studies on the Negative Ion-Molecule Chemistry of Isoflurane and Enflurane

In the present work we present an investigation of the negative ion-molecule chemistry of the anaesthetics isoflurane, ISOF, and enflurane, ENF, in an ion mobility spectrometry/mass spectrometry (IMS/MS), in both air and nitrogen. Hexachloroethane (HCE) was introduced in both air and nitrogen to produce Cl– as a reactant ion. This study was undertaken owing to uncertainties in the chemical processes, which lead to the cluster ions reported in other work (Eiceman et al. Anal. Chem. 61, 1093–1099, 1). In particular for ISOF the product ion observed was ISOF.Cl–, and it was suggested that the Cl– was formed by dissociative electron attachment (DEA) although there was mention of a chlorine containing contaminant. We show in this study that ISOF and ENF do not produce Cl– in an IMS system either by capture of free electrons or reaction with O2–. This demonstrates that the Cl– containing ions, reported in the earlier study, must have been the result of a chlorine containing contaminant as suggested. The failure of ISOF and ENF to undergo DEA was initially surprising given the high calculated electron affinities, but further calculations showed that this was a result of the large positive vertical attachment energies (VAEs). This experimental work has been supported by electronic structure calculations at the B3LYP level, and is consistent with those obtained in a crossed electron-molecular beam two sector field mass spectrometer. An unusual observation is that the monomer complexes of ISOF and ENF with O2– are relatively unstable compared with the dimer complexes.Graphical ᅟ

Free Energies of Redox Half-Reactions from First-Principles Calculations.

Quantitative prediction of the energetics of redox half-reactions is still a challenge for modern computational chemistry. Here, we propose a simple scheme for reliable calculations of vertical ionization and attachment energies, as well as of redox potentials of solvated molecules. The approach exploits linear response approximation in the context of explicit solvent simulations with spherical boundary conditions. It is shown that both vertical ionization energies and vertical electron affinities, and, consequently redox potentials, exhibit linear dependence on the inverse radius of the solvation sphere. The explanation of the linear dependence is provided, and an extrapolation scheme is suggested. The proposed approach accounts for the specific short-range interactions within hybrid DFT and effective fragment potential approach as well as for the asymptotic system-size effects. The computed vertical ionization energies and redox potentials are in excellent agreement with the experimental values.

Electron-atom resonances: The complex-scaled multiconfigurational spin-tensor electron propagator method for the2PBe−shape resonance problem

We propose and develop the complex-scaled multiconfigurational spin-tensor electron propagator (CMCSTEP) technique for theoretical determination of resonance parameters with electron-atom and electron-molecule systems including open-shell and highly correlated atoms and molecules. The multiconfigurational spin-tensor electron propagator (MCSTEP) method developed and implemented by Yeager and co-workers in real space gives very accurate and reliable ionization potentials and attachment energies. The CMCSTEP method uses a complex-scaled multiconfigurational self-consistent field (CMCSCF) state as an initial state along with a dilated Hamiltonian where all of the electronic coordinates are scaled by a complex factor. The CMCSCF was developed and applied successfully to resonance problems earlier. We apply the CMCSTEP method to get ${}^{2}P\phantom{\rule{0.16em}{0ex}}{\text{Be}}^{\ensuremath{-}}$ shape resonance parameters using $14s11p5d,\phantom{\rule{0.16em}{0ex}}14s14p2d$, and $14s14p5d$ basis sets with a $2s2p3d$ complete active space. The obtained values of the resonance parameters are compared to previous results. Here CMCSTEP has been developed and used for a resonance problem. It appears to be among the most accurate and reliable techniques. Vertical ionization potentials and attachment energies in real space are typically within $\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.28em}{0ex}}\text{eV}$ or better of excellent experimental results and full configuration-interaction calculations with a good basis set. We expect the same sort of agreement in complex space.

Application of the Stabilized Koopmans’ Theorem to the Temporary Anion States of Chlorosilanes in Long‐Range Corrected Density Functional Theory

AbstractThe stabilized Koopmans’ theorem (SKT) is very successful in predicting relative vertical electron attachment energies in the Hartree‐Fock theory. It is mainly accomplished by systematically scaling the most diffuse functions in the basis set. Recently, the SKT has been extended to the temporary anion states (TASs) of polyatomic molecules in the long‐range corrected density functional theory. In this paper, this method will be further applied to chlorosilanes for their importance in the chemical processes of the semiconductor industry. Their resonance energies and lifetimes are determined by computing the density of resonance states via SKT. The detailed characteristics of resonance orbitals are then analyzed. It turns out that the lowest unfilled orbitals of chlorosilanes are essentially σ*Si‐Cl in character. Moreover, several TASs with strong Si/Cl “d” character have been identified. These results, definitely, will help us in understanding the peculiar bonding and chemical properties of chlorosilanes.