Ethylenediamine Moiety Research Articles

Structural and tribological studies on the interaction of porcine gastric mucin with non- and cationic-modified β-lactoglobulins

β-lactoglobulin (BLG) is the major whey protein with negative charges at neutral pH in aqueous media. Thus, the interaction with mucins, the major polyanionic component of mucus, is very weak due to the electrostatic repulsion between them. The present study postulates that cationization of BLG molecules may reverse the interaction characteristics between BLG and mucin from repulsive to associative. To this end, cationic-modified BLGs were prepared by grafting positively charged ethylenediamine (EDA) moieties into the negatively charged carboxyl groups on the aspartic and glutamic acid residues and compared with non-modified BLG upon mixing with porcine gastric mucin (PGM). To characterize the structural and conformational features of PGM, non/cationized BLGs, and their mixtures, various spectroscopic approaches, including zeta potential, dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed. Importantly, we have taken surface adsorption with optical waveguide lightmode spectroscopy (OWLS), and tribological properties with pin-on-disk tribometry at the sliding interface as the key approaches to determine the interaction nature between them as mixing PGM with polycations can lead to synergistic lubrication at the nonpolar substrate in neutral aqueous media as a result of an electrostatic association. All the spectroscopic studies and a substantial improvement in lubricity collectively supported a tenacious and associative interaction between PGM and cationized BLGs, but not between PGM and non-modified BLG. This study demonstrates a unique and successful approach to intensify the interaction between BLG and mucins, which is meaningful for a broad range of disciplines, including food science, macromolecular interactions, and biolubrication etc.

Effect of Fusidic Acid and Some Nitrogen-Containing Derivatives on Liposomal and Mitochondrial Membranes.

The paper assesses the membranotropic action of the natural antibiotic fusidic acid (FA) and its derivatives. It was found that a FA analogue with ethylenediamine moiety (derivative 2), in contrast to native FA and 3,11-dioxime analogue (derivative 1), is able to increase the mobility of the lipid bilayer in the zone of lipid headgroups, as well as to induce permeabilization of lecithin liposome membranes. A similar effect of derivative 2 is also observed in the case of rat liver mitochondrial membranes. We noted a decrease in the microviscosity of the mitochondrial membrane and nonspecific permeabilization of organelle membranes in the presence of this agent, which was accompanied by a decrease in mitochondrial Δψ and OXPHOS efficiency. This led to a reduction in mitochondrial calcium retention capacity. The derivatives also reduced the production of H2O2 by mitochondria. The paper considers the relationship between the structure of the tested compounds and the observed effects.

Synthesis of Silver Nanoclusters and Nanoparticles in the Medium of Hyperbranched Polyester Polyamine, and the Morphology and Aggregation Properties of the Metal–Polymer Nanocomposite

A procedure was developed for the single-step synthesis of a metal–polymer nanocomposite based on silver nanoparticles and second-pseudogeneration superbranched polyester functionalized along the periphery with 3-[(2-aminoethyl)amino]propionate. Under the conditions of the synthesis in the medium of H2O or DMSO, hyperbranched polyester decorated with ethylenediamine moieties can act as both a reductant of the nanoscale silver state and a stabilizer of it. The synthesized composite nanomaterial is formed by aggregates of hyperbranched polyester polyamine doped with Ag(0) nanoclusters and nanoparticles of spheroidal symmetry with a face-centered cubic crystal lattice. The hydrodynamic diameter of aggregates and the diameter of particles increase with increasing molar ratioand are 34–90 and 7–14 nm, respectively.

Tris(4-formyl phenyl)amine functionalized mesoporous silica for selective sensing of Al3+ and its separation

Modification of a solid support with a suitable organic moiety offers an opportunity for simultaneous detection and removal of an analyte. Here, functionalized mesoporous silica (FMS-TPA-en) has been synthesized with SBA-15 silica as the solid support by successive functionalization of the inorganic mesoporous silica framework with 3-aminopropyl triethoxysilane, tris(4-formyl phenyl)amine and ethylenediamine. The materials in successive stages have been characterized in the solid state using powder X-ray diffraction, nitrogen adsorption/desorption and electron microscopic studies, FT-IR spectra and thermogravimetric analysis. Photoluminescence studies of the material reveal that it is able to sense Al3+ ion selectively among other relevant cations in methanol. Fluorescence of FMS-TPA-en increases at 470 nm upon excitation at 390 nm in the presence of the trivalent cation. It has also been observed that the intensity of the functionalized material remains unchanged in the presence of most of the other relevant metal ions. Here, the combination of tris(4-formyl phenyl)amine and ethylenediamine moieties acts as the fluorophoric units having binding pocket for the binding of metal ion(s). Fluorescence enhancement occurs via PET and CHEFF mechanisms. It has also been observed that the binding of the probe to Al3+ is reversible in nature. FMS-TPA-en has been used for the separation of Al3+ with high efficiency and the solid probe could be easily recycled.

Aerogel-Based Single-Ion Magnets: A Case Study of a Cobalt(II) Complex Immobilized in Silica

The chemical immobilization of cobalt(II) ions in a silica aerogel matrix enabled the synthesis of the first representative example of aerogel-based single-ion magnets. For the synthesis of the lyogels, methyl-trimethoxysilane and N-3-(trimethoxysilyl)propyl ethylenediamine were co-hydrolyzed, then the ethylenediamine groups that were immobilized on the silica matrix enabled the subsequent binding of cobalt(II) ions. Lyogels with various amounts of ethylenediamine moieties (0.1-15 mol %) were soaked in isopropanol solutions of cobalt(II) nitrate and further supercritically dried in carbon dioxide to obtain aerogels with a specific surface area of 210-596 m2·g-1, an apparent density of 0.403-0.740 cm3·g-1 and a porosity of 60-78%. The actual cobalt content in the aerogels was 0.01-1.50 mmol per 1 g of SiO2, which could easily be tuned by the concentration of ethylenediamine moieties in the silica matrix. The introduction of cobalt(II) ions into the ethylenediamine-modified silica aerogel promoted the stability of the diamine moieties at the supercritical drying stage. The molecular prototype of the immobilized cobalt(II) complex, bearing one ethylenediamine ligand [Co(en)(MeCN)(NO3)2], was synthesized and structurally characterized. Using magnetometry in the DC mode, it was shown that cobalt(II)-modified silica aerogels exhibited slow magnetic relaxation in a nonzero field. A decrease in cobalt(II) concentration in aerogels from 1.5 mmol to 0.14 mmol per 1 g of SiO2 resulted in a weakening of inter-ion interactions; the magnetization reversal energy barrier likewise increased from 4 to 18 K.

Synthesis and cytotoxicity of betulin and betulinic acid derived 30-oxo-amides

Betulin and betulinic acid derived 30-oxo-amides were prepared by hydroboration, subsequent oxidation and amidation; these novel compounds were screened for their cytotoxic activity by SRB assays. All of the compounds showed significant cytotoxic activity for different human tumor cell lines. Small changes in the structure, however, resulted in significant changes in the cytotoxicity of the compounds. Of special interest were compounds 11 and 12, each holding an extra ethylenediamine moiety. These C-30 amides which showed low EC50 values, and both of them acted mainly by apoptosis.

Synthesis of 3-O-Acetyl-11-keto-β-boswellic Acid (AKBA)-Derived Amides and Their Mitochondria-Targeted Antitumor Activities

In this study, we synthesized a series of amide and mitochondria-targeted derivatives with 3-O-acetyl-11-keto-β-boswellic acid (AKBA) as the parent structure and an ethylenediamine moiety as the link chain. Compound 5e, a mitochondrial-targeting potential derivative, showed significantly stronger antitumor activity than that of AKBA, and it could induce vacuolization of A549 cells and stimulate the production of reactive oxygen species (ROS) in a time- and concentration-dependent manner. The antioxidant N-acetylcysteine (NAC) could inhibit the ROS level but could not suppress vacuolization and cell death induced by 5e. Further studies demonstrated that 5e caused abnormal opening of mitochondrial permeability transition pore (MPTP) and a decrease of mitochondrial membrane potential; additionally, it caused cell cycle arrest in G0/G1 but did not induce apoptosis. 5e represented a compound with improved antiproliferative effects for cancer therapy working through new mechanisms.

Cesium ion adsorption and desorption on electrospun mesoporous silica nanofibers immobilized with Prussian blue

To fabricate an efficient Cs ion adsorbent and prevent unexpected loss of Prussian blue (PB) colloidal particles during use, PB was immobilized on the surface of electrospun mesoporous silica nanofibers (MSFs) via a newly developed method of double exposure to Fe (III) ions. To introduce PB on MSFs, the MSFs were functionalized with ethylenediamine moiety to bind to Fe (III) ions, which would firmly anchor PB. MSFs were pretreated with Fe (III) ions and exposed to K4 [Fe(II) (CN)6] to form PB. We found that this process did not provide a sufficient PB amount on the MSFs. To increase the PB amount, after initial PB formation, the MSFs were treated with Fe (III) ions again so that the unreacted K4 [Fe(II) (CN)6] remaining on the MSFs could become PB. An investigation of the adsorption isotherms and kinetics of the nanofibrous adsorbent indicated that monolayer chemisorption had occurred. The maximum Cs ion adsorption capacity using the method of double exposure to Fe (III) ions was determined to be 14.66 mg/g, which was higher by a factor of 2.24 than the case that was not prepared by this method. Cs ions were selectively adsorbed over other cations and could be removed in both acidic and basic conditions, presumably because of the robust MSFs.

Polymeric RNAi Constructs Tailored with Appreciable Transcellular Trafficking Functions for Potential Suppression of Parathyroid Hormone Production.

Polymeric small interfering RNA (siRNA) conjugate was elaborated to sequentially circumvent the predefined biological barriers encountered in the journey of transcellular delivery of siRNA into cytosol. Herein, classic ring-opening polymerization was employed for synthesis of well-defined poly(amino acid) derivatives possessing an array of carboxyl groups in an attempt to resemble the structural characteristics of hyaluronan. Furthermore, the hyaluronan-like synthetic was conjugated with a multiple of siRNA through a glutathione (GSH)-responsive disulfide linkage. The siRNA conjugate appeared to utilize the hyaluronan-specific receptors of CD44 for cell internalization, indicating similar functionalities to our hyaluronan-mimicking synthetic. Furthermore, the carboxyl groups of hyaluronan-like synthetics were designed to be selectively detached in subcellular acidic endosomes/lysosomes and transform into the cytomembrane-disruptive flanking ethylenediamine moieties, which appeared to be crucial in facilitating translocation of siRNA payloads from entrapment and degradation in lysosomes toward the cytosol. Eventually, active siRNA could be smoothly released from the synthetic due to the GSH cleavage disulfide linkage (disulfide), consequently accounting for potent RNA knockdown activities (>90%) toward cancerous cells. In addition, appreciable knockdown of parathyroid hormone was also achieved from our proposed siRNA conjugates in parathyroid cells. Hence, the elaborated siRNA conjugate showed tremendous potential in treatment of hyperparathyroidism, and could be developed further for systemic RNA interference (RNAi) therapeutics. Moreover, this study could also be the first example of a synthetic mimic to hyaluronan acquiring its functionalities, which could have important implications for further development of biomimic materials in pursuit of biomedical applications.

Development of a cobalt(iii)-based ponatinib prodrug system.

Receptor tyrosine kinase inhibitors have become a central part of modern targeted cancer therapy. However, their curative potential is distinctly limited by both rapid resistance development and severe adverse effects. Consequently, tumor-specific drug activation based on prodrug designs, exploiting tumor-specific properties such as hypoxic oxygen conditions, is a feasible strategy to widen the therapeutic window. After proof-of-principal molecular docking studies, we have synthesized two cobalt(iii) complexes using a derivative of the clinically approved Abelson (ABL) kinase and fibroblast growth factor receptor (FGFR) inhibitor ponatinib. Acetylacetone (acac) or methylacetylacetone (Meacac) have been used as ancillary ligands to modulate the reduction potential. The ponatinib derivative, characterized by an ethylenediamine moiety instead of the piperazine ring, exhibited comparable cell-free target kinase inhibition potency. Hypoxia-dependent release of the ligand from the cobalt(iii) complexes was proven by changed fluorescence properties, enhanced downstream signaling inhibition and increased in vitro anticancer activity in BCR-ABL- and FGFR-driven cancer models. Respective tumor-inhibiting in vivo effects in the BCR-ABL-driven K-562 leukemia model were restricted to the cobalt(iii) complex with the higher reduction potential and confirmed in a FGFR-driven urothelial carcinoma xenograft model. Summarizing, we here present for the first time hypoxia-activatable prodrugs of the clinically approved tyrosine kinase inhibitor ponatinib and a correlation of the in vivo activity with their reduction potential.

Structural and CO2 Capture Properties of Ethylenediamine-Modified HKUST-1 Metal–Organic Framework

The high structural and compositional flexibility of metal–organic frameworks (MOFs) shows their great potential for CO2 capture and utilization in accordance with the environmental guidelines of low-carbon technology developments. HKUST-1 as one of the most intensively studied representatives of MOFs for such purposes excels because of its simplicity of production and high ability to tune its intrinsic properties by various functionalization processes. In the present work, ethylenediamine functionalization was performed for the first time in order to thoroughly investigate the amine sorption sites’ impact on the CO2 capture performance of HKUST-1. The placement of ethylenediamine moieties on Cu2+ free-metal sites has been examined in detail and confirmed by using various spectroscopic techniques such as Fourier transform infrared spectroscopy, electron paramagnetic resonance, Raman, and Cu K-edge extended X-ray absorption fine structure/X-ray absorption near edge structure. N2 and CO2 sorption tests have proven that the functionalization reduces both the specific surface area and the CO2 sorption capacity, but on the other hand, it increases the binding energy by 85% (from −20.3 kJ/mol to −36.8 kJ/mol) and CO2/N2 selectivity at 0.15/0.85 bar by 100% and notably improves the kinetics of adsorption in comparison to the pristine HKUST-1 material.

Production and physicochemical characterization of a new amine derivative of gellan gum and rheological study of derived hydrogels

The production of an amine derivative of gellan gum, named GG-EDA, was here obtained by functionalizing the polysaccharide backbone with pendant ethylenediamine moieties. The obtained derivative was characterized by spectroscopic, colorimetric, chromatographic and rheological analyses to study the effect of the free amino groups on the physicochemical properties of the macromolecule. A titration experiment was conducted to study the acid-base dissociation constants in aqueous media for the carboxylic and amino groups in the GG-EDA and to shed light on the possibility that the derivative shows a polyampholyte structure under physiological conditions.The rheological analysis conducted on both physical and chemical hydrogels based on GG-EDA revealed that the presence of amino groups plays a fundamental role in influencing the viscoelastic properties and stability of the produced samples.

Oxadiazolylthiazoles as novel and selective antifungal agents

Studying the structure-activity relationships (SAR) of oxadiazolylthiazole antibiotics unexpectedly led us to identify ethylenediamine- and propylenediamine-analogs as potential antimycotic novel lead structures. Replacement of the ethylenediamine moiety for the lead compound 7 with cis-diaminocyclohexyl group (compound 18) significantly enhanced the antifungal activity. In addition to the high safety margin of 18 against mammalian cells, it showed highly selective broad-spectrum activity against fungal cells without inhibiting the human normal microbiota. The antifungal activity of 18 was investigated against 20 drug-resistant clinically important fungi, including Candida species, Cryptococcus, and Aspergillus fumigatus strains. In addition to the low MIC values that mostly ranged between 0.125 and 2.0 μg/mL, compound 18 outperformed fluconazole in disrupting mature Candida biofilm.

Fluorophoric Conjugate of N-Alkyl Naphthalimide in Sodium Dodecyl Sulfate As a Tunable and Sustainable Sensing System: Differential Sensing of Zn2+ and Al3+ and the Application of Its Zn2+ Complex in Detecting Dipicolinic Acid, a Component of Anthrax Bacterial Endospores

A naphthalimide-based fluorophore has been conjugated by an octyl chain on one side and an ethylenediamine (“en”) moiety on the other to result in a conjugate (L1) that was adapted to exhibit selective ion sensing. Since L1 is not a receptor for metal ions in water or in organic solvents, this has been introduced into the self-assembly formed by the surfactant, i.e., sodium dodecyl sulfate (SDS), and its ion sensing was studied by varying the concentration of the SDS since it is known to form premicellar as well as micellar assemblies. Thus, the L1 was successfully converted to a specific, selective, and sustainable chemo-receptor system for Al3+ and Zn2+ with the support of such assemblies of SDS. The selectivity was among three trivalent and eight divalent ions studied. The ion recognition ability was dependent on the nature of the assembly of SDS formed and is efficient in the premicellar media. Both the Al3+ and Zn2+ were differentially recognized just by tuning the SDS concentration. The results were ratified by comparing with several control experiments. The excited-state lifetime measurements and the size of these assemblies measured by dynamic light scattering (DLS) reveal that at >4 mM SDS concentration (critical micellar concentration is 8 mM) the probe L1 is not accessible for any of the metal ions studied. The two other derivatives possessing a shorter (propyl, L2) and a longer (dodecyl, L3) alkyl chain showed that the L1 with an octyl chain performs much better at all the premicellar SDS concentrations. The Zn2+-bound assembly of L1 in 4 mM SDS was demonstrated for sensing the dipicolinic acid (DPA) which happens to be an endospore component of anthrax bacteria. This study was extended to several other carboxylic acid derivatives which would act as control molecular systems. Even in the DPA sensing, the assemblies possessing an octyl derivative stand out when compared to the propyl or the dodecyl derivatives.

A new series of lanthanide complexes with the trans-disubstituted Py2[18]aneN6 macrocyclic ligand: synthesis, structures and properties

New lanthanide complexes with the trans-disubstituted macrocyclic ligand Py2[18]aneN6 (denoted as L1) were successfully synthesized. The coordination properties of compound L1 towards different lanthanide metal ions (Ln = La–Yb, except Lu) were explored, and structural studies have been carried out both in the solid state and in aqueous solution. In all cases, complexes with a 1:1 metal:ligand molar ratio were obtained. The crystalline structures of the following compounds: [H4L1](NO3)4, [CeL1(NO3)2](NO3) and [SmL1(NO3)2](NO3) have been characterized by single crystal X-ray diffraction. In both complexes, the asymmetric unit contains the cation complex [LnL1(NO3)2]+ (Ln = Ce3+, Sm3+) which consist of a mononuclear endomacrocyclic backbone whilst the ten coordination environment is completed by two bidentade nitrate ions. The two five membered chelate rings formed by the ethylenediamine moieties adopt (δδ) [or (λλ)] conformations and also presented a C2 symmetry (as observed in solution by NMR).

3D Ferroconcrete‐Like Aminated Carbon Nanotubes Network Anchoring Sulfur for Advanced Lithium–Sulfur Battery

AbstractTo address the serious capacity fading in lithium–sulfur batteries, a 3D ferroconcrete‐like aminated carbon nanotubes network with polyaniline coating as an effective sulfur host to contain polysulfide dissolution is presented here. In this composite, the cross‐linked aminated carbon nanotubes framework provides a fast charge transport pathway and enhancement in the reaction kinetics of the active material to greatly improve the rate capability and sulfur utilization. The ethylenediamine moieties provide strong adhesion of polar discharge products to nonpolar carbon surfaces and thus efficiently prevent polysulfide dissolution to improve the cycle stability, confirmed by density functional theory calculations. The outside polyaniline layers structurally restrain polysulfides to prevent the shuttle effect and active material loss. Benefiting from these advantages, the synthesized composite exhibits a high initial capacity of 1215 mAh g−1 and a capacity of 975 mAh g−1 after 200 cycles at 0.2 C. Even after 200 cycles at 0.5 C, a capacity of 735 mAh g−1 can be maintained, among the best performance reported. The strategy in this work can shed some light on modifying nonpolar carbon surfaces via the amination process to chemically attach sulfur species for high‐performance lithium–sulfur batteries.

An Ethylenediamine‐based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials

AbstractPolyzwitterions are employed as coating polymers for biomaterials to induce an antifouling property on the surface. Fine‐tuning the betaine structure switches the antifouling property to be interactive with anionic tissue constituents in response to a tumorous pH gradient. The ethylenediamine moiety in the carboxybetaine enabled stepwise protonation and initiated the di‐protonation process around tumorous pH (6.5). The net charge of the developed polyzwitterion (PGlu(DET‐Car)) was thus neutral at pH 7.4 for antifouling, but was cationic at pH 6.5 for interaction with anionic constituents. Quantum dots coated with PGlu(DET‐Car) exhibited comparable stealth and enhanced tumor accumulation relative to the PEG system. The present study provides a novel design of smart switchable polyzwitterion based on a precise control of the net charge.

An Ethylenediamine‐based Switch to Render the Polyzwitterion Cationic at Tumorous pH for Effective Tumor Accumulation of Coated Nanomaterials

Polyzwitterions are employed as coating polymers for biomaterials to induce an antifouling property on the surface. Fine-tuning the betaine structure switches the antifouling property to be interactive with anionic tissue constituents in response to a tumorous pH gradient. The ethylenediamine moiety in the carboxybetaine enabled stepwise protonation and initiated the di-protonation process around tumorous pH (6.5). The net charge of the developed polyzwitterion (PGlu(DET-Car)) was thus neutral at pH 7.4 for antifouling, but was cationic at pH 6.5 for interaction with anionic constituents. Quantum dots coated with PGlu(DET-Car) exhibited comparable stealth and enhanced tumor accumulation relative to the PEG system. The present study provides a novel design of smart switchable polyzwitterion based on a precise control of the net charge.

A Comparative Study on Micellar and Solubilizing Behavior of Three EO-PO Based Star Block Copolymers Varying in Hydrophobicity and Their Application for the In Vitro Release of Anticancer Drugs.

The temperature and pH dependent self-assembly of three star shaped ethylene oxide-propylene oxide (EO-PO) block copolymers (Tetronics® 304, 904 and 908) with widely different hydrophobicity was examined in aqueous solutions. Physico-chemical methods viz. viscosity, cloud point, solubilization along with thermal, scattering and spectral techniques shows strongly temperature and salt dependent solution behavior. T304 possessing low molecular weight did not form micelles; moderately hydrophilic T904 remained as micelles at ambient temperature and showed micellar growth while very hydrophilic T908 formed micelles at elevated temperatures. The surface activity/micellization/solubilization power was favored in the presence of salt. The copolymers turn more hydrophilic in acidic pH due to protonation of central ethylene diamine moiety that hinders micelle formation. The solubilization of a model insoluble azo dye 1-(o-Tolylazo)-2-naphthol (Orange OT) and hydrophobic drugs (quercetin and curcumin) for copolymer solutions in aqueous and salt solutions are also reported. Among the three copolymers, T904 showed maximum solubility of dye and drugs, hence the in vitro release of drugs from T904 micelles was estimated and the effect on cytotoxicity of loading the drugs in T904 micelles was compared with the cytotoxicity of free drugs on the CHO-K1 cells. The results from the present work provide a better insight in selection of Tetronics® for their application in different therapeutic applications.

Characterization of the one-electron oxidized Cu(II)-salen complexes with a side chain aromatic ring: the effect of the indole ring on the Cu(II)-phenoxyl radical species.

To gain insights into the role of the proximal indole ring in the redox-active metal center as seen in galactose oxidase, we prepared the Cu(II)-salen-type complexes having a pendent indol-3-ylmethyl (1), methyl (2) or benzyl (3) group substituted on the ethylenediamine moiety and investigated the structures and redox properties by various physicochemical methods and theoretical calculations. Neutral complexes 1, 2, and 3 showed no significant difference in the UV-Vis-NIR and EPR spectra. One-electron oxidation of 1, 2, and 3 by addition of 1 equiv. of thianthrenyl radical gave [1]SbCl 6 , [2]SbCl 6 , and [3]SbCl 6 , respectively, which could be assigned to relatively localized phenoxyl radical species. The cyclic and differential pulse voltammograms of [1]SbCl 6 showed two redox waves with a large separation between the first and second redox potentials compared with the separations observed for [2]SbCl 6 and [3]SbCl 6 . This suggests that [1]SbCl 6 is more stabilized than [2]SbCl 6 and [3]SbCl 6 . The NIR band of [1]SbCl 6 showed a larger blue shift than that of [2]SbCl 6 and [3]SbCl 6 . The EPR spectrum of [2]SbCl 6 exhibited an intense signal at the g value of 2 due to partial disproportionation to form the EPR active two-electron oxidized complex [2] 2+ , while the EPR intensity of [1]SbCl 6 was much weaker than that of [2]SbCl 6 . These results indicate that the pendent indole moiety stabilizes the Cu(II)-phenoxyl radical in [1]SbCl 6 most probably by stacking with the phenoxyl moiety, which is further supported by DFT calculations.