Interfacial Water Molecules as Agents for Phase Change Control and Proton Conductivity Enhancement in the Ammonium Vanadyl Tartrate System.

This study demonstrates the reversible structural transformation, single-crystal-to-single-crystal, of the ammonium vanadyl (L-tartrate) complex salt from the hydrate phase to the anhydrous phase. The transformation can be initiated by stimuli, such as temperature, humidity, or vacuum conditions. The hydrate and anhydrous phases exhibit a tetragonal structure (P41212), with marked differences in hydrogen bonding due to the presence or absence of one water molecule per asymmetric unit. The intricate relationship between crystal packing and intermolecular interactions in the hydrate phase was investigated by crystallographic charge density analysis revealing, at the molecular level, the reasons for the observed 5 orders of magnitude higher proton conductivity of the hydrate phase compared to that of the anhydrous phase. To gain further insight into the processes occurring at the surfaces of grain boundaries and the proton transfer mechanisms in this system, rehydration of the complex salt was carried out by using D2O instead of H2O and monitored by in situ ATR-FTIR spectroscopy. The results highlight the critical role of interfacial water molecules in driving structural transformations and influencing proton conductivity.

New resveratrol analogs as improved biologically active structures: Design, synthesis and computational modeling.

New analogs of the well-known bioactive trihydroxy-stilbene resveratrol were synthesized to investigate their potential biological activity. The focus was on assessing their ability to inhibit cholinesterase enzymes (ChEs) and their antioxidative properties, which were thoroughly examined. New resveratrol analogs were synthesized through Wittig or McMurry reaction in moderate-to-good yields. In all synthetic pathways, mixtures of cis- and trans-isomers were obtained, then separated by chromatography, and trans-isomers were isolated as targeted structures. The stilbene derivatives underwent evaluation for antioxidant activity (AOA) using DPPH and CUPRAC assay, and their potential to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was also measured. The biological tests have shown that the same compounds exhibited significant antioxidative and butyrylcholinesterase inhibitory potential, as evidenced by lower IC50 values compared to the established standards, trans-resveratrol, and galantamine, respectively. Additionally, molecular docking of the selected synthesized potential inhibitors to the enzyme's active site was performed, followed by assessing the complex stability using molecular dynamics simulation lasting 100 ns. Lastly, the new compounds underwent examination to determine their potential mutagenicity.

High Proton Conductivity of Magnetically Ordered 2D Oxalate-Bridged [MnIICrIII] Coordination Polymers with Irregular Topology.

Two heterometallic coordination polymers {[NH(CH3)2(C2H5)]8[Mn4Cl4Cr4(C2O4)12]}n (1) and {[NH(CH3)-(C2H5)2]8[Mn4Cl4Cr4(C2O4)12]}n (2) were obtained by slow evaporation of an aqueous solution containing the building block [A]3[Cr(C2O4)3] [A = (CH3)2(C2H5)NH+ or (CH3)(C2H5)2NH+] and MnCl2·2H2O. The isostructural compounds comprise irregular two-dimensional (2D) oxalate-bridged anionic layers [Mn4Cl4Cr4(C2O4)12]n8n- with a Shubnikov plane net fes topology designated as (4·82), interleaved by the hydrogen-bonded templating cations (CH3)2(C2H5)NH+ (1) or (CH3)(C2H5)2NH+ (2). They exhibit remarkable humidity-sensing properties and very high proton conductivity at room temperature [1.60 × 10-3 (Ω·cm)-1 at 90% relative humidity (RH) of 1 and 9.6 × 10-4 (Ω·cm)-1 at 94% RH of 2]. The layered structure facilitates the uptake of water molecules, which contributes to the enhancement of proton conductivity at high RH. The better proton transport observed in 1 compared to that in 2 can be tentatively attributed to the higher hydrophilicity of the cations (CH3)2(C2H5)NH+, which is closely related to their affinity for water molecules. The original topology of the anionic networks in both compounds leads to the development of interesting magnetic phases upon cooling. The magnetically ordered ground state can be described as the coupling of ferromagnetic spin chains in which Mn2+ and Cr3+ ions are bridged by bis(bidentate) oxalate groups into antiferromagnetic planes through monodentate-bidentate oxalate bridges in the layers, which are triggered to long-range order below temperature 4.45 K via weaker interlayer interactions.

Light-Induced Intramolecular Electron Transfer in a 1D [CuFe] Coordination Polymer Containing the [Fe(C2O4)3]3- Core.

A one-dimensional (1D) ladder-like coordination polymer {NH4[{Cu(bpy)}2(C2O4)Fe(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) containing [Cu(bpy)(µ-C2O4)Cu(bpy)]2+ cationic units linked by oxalate groups of [Fe(C2O4)3]3- building blocks was investigated as a new type of photoactive solid-state system. It exhibits a photocoloration effect when exposed to direct sunlight or UV/vis irradiation. The photochromic properties and mechanism were studied by powder and single-crystal X-ray diffraction, UV/vis diffuse reflectance, IR and electron paramagnetic resonance spectroscopy, magnetization and impedance measurements, and density functional theory calculations. The process of photochromism involves simultaneous intramolecular electron transfers from the oxalate ligand to Fe(III) and to [CuII(bpy)(µ-C2O4)CuII(bpy)]2+, leading to the reduction of the metal centers to the electronic states Fe(II) and Cu(I), accompanied by the release of gaseous CO2.

New Thienobenzo/Naphtho-Triazoles as Butyrylcholinesterase Inhibitors: Design, Synthesis and Computational Study.

This study aims to test the inhibition potency of new thienobenzo/naphtho-triazoles toward cholinesterases, evaluate their inhibition selectivity, and interpret the obtained results by molecular modeling. The synthesis of 19 new thienobenzo/naphtho-triazoles by two different approaches resulted in a large group of molecules with different functionalities in the structure. As predicted, most prepared molecules show better inhibition of the enzyme butyrylcholinesterase (BChE), considering that the new molecules were designed according to the previous results. Interestingly, the binding affinity of BChE for even seven new compounds (1, 3, 4, 5, 6, 9, and 13) was similar to that reported for common cholinesterase inhibitors. According to computational study, the active thienobenzo- and naphtho-triazoles are accommodated by cholinesterases through H-bonds involving one of the triazole's nitrogens, π-π stacking between the aromatic moieties of the ligand and aromatic residues of the active sites of cholinesterases, as well as π-alkyl interactions. For the future design of cholinesterase inhibitors and search for therapeutics for neurological disorders, compounds with a thienobenzo/naphtho-triazole skeleton should be considered.

The Benzothiazine Core as a Novel Motif for DNA-Binding Small Molecules.

A new series of 4H-1,3-benzothiazine dyes were prepared and fully characterized in an aqueous medium. Benzothiazine salts were synthesized either through the classical synthetic pathway using Buchwald-Hartwig amination or through economical and environmentally friendly electrochemical synthesis. The latest synthetic approach employs successful electrochemical intramolecular dehydrogenative cyclization of N-benzylbenzenecarbothioamides to form 4H-1,3-benzothiazines. 4H-1,3-Benzothiazines were evaluated as novel DNA/RNA probes. Through the use of several methods such as UV/vis spectrophotometric titrations, circular dichroism and thermal melting experiments, the binding of four benzothiazine-based molecules to polynucleotides was examined. Compounds 1 and 2 acted as DNA/RNA groove binders, thus suggesting the potential of these compounds as novel DNA/RNA probes. This is a proof-of-concept study and will be expanded to include SAR/QSAR studies.

Hydrogen Bonding Drives Helical Chirality via 10-Membered Rings in Dipeptide Conjugates of Ferrocene-1,1'-Diamine.

Considering the enormous importance of protein turns as participants in various biological events, such as protein-protein interactions, great efforts have been made to develop their conformationally and proteolytically stable mimetics. Ferrocene-1,1'-diamine was previously shown to nucleate the stable turn structures in peptides prepared by conjugation with Ala (III) and Ala-Pro (VI). Here, we prepared the homochiral conjugates of ferrocene-1,1'-diamine with l-/d-Phe (32/35), l-/d-Val (33/36), and l-/d-Leu (34/37) to investigate (1) whether the organometallic template induces the turn structure upon conjugation with amino acids, and (2) whether the bulky or branched side chains of Phe, Val, and Leu affect hydrogen bonding. Detailed spectroscopic (IR, NMR, CD), X-ray, and DFT studies revealed the presence of two simultaneous 10-membered interstrand hydrogen bonds, i.e., two simultaneous ß-turns in goal compounds. A preliminary biological evaluation of d-Leu conjugate 37 showed its modest potential to induce cell cycle arrest in the G0/G1 phase in the HeLa cell line but these results need further investigation.

Resveratrol-Maltol and Resveratrol-Thiophene Hybrids as Cholinesterase Inhibitors and Antioxidants: Synthesis, Biometal Chelating Capability and Crystal Structure.

New resveratrol-thiophene and resveratrol-maltol hybrids were synthesized as cholinesterase inhibitors and antioxidants. As with photostability experiments, biological tests also found remarkable differences in the properties and behavior of thiophene and maltol hybrids. While resveratrol-thiophene hybrids have excellent inhibitory and antioxidant properties (similar to the activity of reference drug galantamine), maltols have been proven to be weaker inhibitors and antioxidants. The molecular docking of selected active ligands gave insight into the structures of docked enzymes. It enabled the identification of interactions between the ligand and the active site of both cholinesterases. The maltols that proved to be active cholinesterase inhibitors were able to coordinate Fe3+ ion, forming complexes of 1:1 composition. Their formation constants, determined by spectrophotometry, are very similar, lgK = 11.6-12.6, suggesting that Fe3+ binds to the common hydroxy-pyranone moiety and is hardly affected by the other aromatic part of the ligand. Accordingly, the characteristic bands in their individual absorption spectra are uniformly red-shifted relative to those of the free ligands. The crystal structures of two new resveratrol-maltol hybrids were recorded, giving additional information on the molecules' intermolecular hydrogen bonds and packing. In this way, several functionalities of these new resveratrol hybrids were examined as a necessary approach to finding more effective drugs for complicated neurodegenerative diseases.

Conformational Preferences and Antiproliferative Activity of Peptidomimetics Containing Methyl 1'-Aminoferrocene-1-carboxylate and Turn-Forming Homo- and Heterochiral Pro-Ala Motifs.

The concept of peptidomimetics is based on structural modifications of natural peptides that aim not only to mimic their 3D shape and biological function, but also to reduce their limitations. The peptidomimetic approach is used in medicinal chemistry to develop drug-like compounds that are more active and selective than natural peptides and have fewer side effects. One of the synthetic strategies for obtaining peptidomimetics involves mimicking peptide α-helices, ß-sheets or turns. Turns are usually located on the protein surface where they interact with various receptors and are therefore involved in numerous biological events. Among the various synthetic tools for turn mimetic design reported so far, our group uses an approach based on the insertion of different ferrocene templates into the peptide backbone that both induce turn formation and reduce conformational flexibility. Here, we conjugated methyl 1'-aminoferrocene-carboxylate with homo- and heterochiral Pro-Ala dipeptides to investigate the turn formation potential and antiproliferative properties of the resulting peptidomimetics 2-5. Detailed spectroscopic (IR, NMR, CD), X-ray and DFT studies showed that the heterochiral conjugates 2 and 3 were more suitable for the formation of ß-turns. Cell viability study, clonogenic assay and cell death analysis showed the highest biological potential of homochiral peptide 4.

Structural, Electrical, and Magnetic Versatility of the Oxalate-Based [CuFe] Compounds Containing 2,2':6',2″-Terpyridine: Anion-Directed Synthesis.

The heterodimetallic [CuFe] compounds [CuII4(terpy)4Cl5][FeIII(C2O4)3]·10H2O (1;terpy = 2,2':6',2''-terpyridine), [CuII2(H2O)2(terpy)2(C2O4)][CuIIFeIII(CH3OH)(terpy)(C2O4)3]2 (2), and {[Cu2IIFeIII(H2O)(terpy)2(C2O4)7/2]·6H2O}n (3) were obtained using building block approach, from reaction of aqueous solution of [Fe(C2O4)3]3- and a methanol solution containing Cu2+ ions and terpy by the layering technique. Interestingly, by changing only the anion of the starting salt of copper(II), Cu(NO3)2·3H2O instead of CuCl2·2H2O, an unexpected change in the type of bridge, oxalate (2 and 3) versus chloride (1), was achieved, thus affecting the overall structural architecture. Two polymorphs of 3D coordination polymer [CuIIFeII2(H2O)(terpy)(C2O4)3]n (4), crystallizing in the triclinic (a) and monoclinic (b) space groups, were formed hydrothermally, depending on whether CuCl2·2H2O or Cu(NO3)2·3H2O was added to the water, besides K3[Fe(C2O4)3]·3H2O and terpy, respectively. Under hydrothermal conditions iron(III) from initial building block is reduced to the divalent state, creating 2D honeycomb [FeII2(C2O4)3]n2n- layers, which are bridged by [Cu(H2O)(terpy)]2+ cations. Compounds were investigated by single-crystal X-ray diffraction, IR, and impedance spectroscopies, magnetization measurements, and density functional theory (DFT) calculations. In compounds 1 and 2, 0D magnetism is observed, with 1 having a ground-state spin of 1 due to different interactions through chloride bridges of Cu2+ ions in tetramer [CuII4(terpy)4Cl5]3+ and 2 showing strong antiferromagnetic coupling of Cu2+ ions mediated by oxalate ligand in [CuII2(H2O)2(terpy)2(C2O4)]2+ and weak ones between Cu2+ and Fe3+ ions through oxalate bridge in [CuIIFeIII(CH3OH)(terpy)(C2O4)3]-. Polymer 4 exhibits antiferromagnetic phase transition at 25 K: The [FeII2(C2O4)3]n2n- layers are antiferromagnetically ordered, and a small amount of interlayer interaction is transferred through [Cu(H2O)(terpy)]2+ cations via Oox-Cu-Oox bridges. Additionally, compounds 1 and 2 are electrical insulators, while 4a and 4b show proton conductivity.

A simple and easy to perform synthetic route to functionalized thienyl bicyclo[3.2.1]octadienes.

In order to prepare novel polycyclic derivatives of bicyclo[3.2.1]octadiene systems fused with a thiophene ring, photochemical cyclization and aldol condensation reactions were carried out. The starting substrates were easily obtained by a Vilsmeier-Haack reaction of bicyclo[3.2.1]octadiene thiophene derivatives with dimethylformamide. From the obtained carbaldehydes, novel methyl, methoxy, and cyano-substituted styryl thienobenzobicyclo[3.2.1]octadiene derivatives were synthesized through Wittig reactions and subjected to photochemical cyclization, in terms of obtaining the new annulated structures. As part of this study, the aldol reaction of the starting 2-substituted carbaldehyde with acetone was also performed, which produced the thieno-fused benzobicyclo[3.2.1]octadiene compound with an extended conjugation.

A Crystallographic Charge Density Study of the Partial Covalent Nature of Strong N⋠⋠⋠Br Halogen Bonds.

The covalent nature of strong N-Br⋅⋅⋅N halogen bonds in a cocrystal (2) of N-bromosuccinimide (NBS) with 3,5-dimethylpyridine (lut) was determined from X-ray charge density studies and compared to a weak N-Br⋅⋅⋅O halogen bond in pure crystalline NBS (1) and a covalent bond in bis(3-methylpyridine)bromonium cation (in its perchlorate salt (3). In 2, the donor N-Br bond is elongated by 0.0954 Å, while the Br⋅⋅⋅acceptor distance of 2.3194(4) is 1.08 Šshorter than the sum of the van der Waals radii. A maximum electron density of 0.38 e Å-3 along the Br⋅⋅⋅N halogen bond indicates a considerable covalent contribution to the total interaction. This value is intermediate to 0.067 e Å-3 for the Br⋅⋅⋅O contact in 1, and approximately 0.7 e Å-3 in both N-Br bonds of the bromonium cation in 3. A calculation of the natural bond order charges of the contact atoms, and the σ*(N1-Br) population of NBS as a function of distance between NBS and lut, have shown that charge transfer becomes significant at a Br⋅⋅⋅N distance below about 3 Å.

Pancake Bonding in π-Stacked Trimers in a Salt of Tetrachloroquinone Anion.

The crystal structure of [4-damp])2 [Cl4 Q]3 (4-damp=4-dimethylamino-N-methylpyridinium, Cl4 Q=tetrachloroquinone) salt is built up from slipped columnar stacks of quinoid rings composed of closely bound trimers with the intra-trimer separation distance of 2.84 Šand total charge of -2 whereas the inter-trimer distance is 3.59 Å. The individual rings exhibit partial negative charges that are distributed unevenly among the three Cl4 Qs in the trimer. The strong interactions within a trimer (Cl4 Q)32- have a partially covalent character with two-electron/multicentered bonding, that is extended over three rings, plausibly termed as "pancake bonding". The electron pairing within this multicentre bond leads to the fact that the crystals are diamagnetic and act as insulators. The studies of the structure and nature of bonding are based on X-ray charge density analysis and density functional theory.

Helically Chiral Peptides That Contain Ferrocene-1,1'-diamine Scaffolds as a Turn Inducer.

A series of peptides that contain homo- and heterochiral Ala-Pro sequences attached to the turn-inducing ferrocene-1,1'-diamine scaffold were synthesized. The effects of the backbone chirality and the N-terminal group (Boc/Ac) on the conformational properties of the novel peptidomimetics were thoroughly explored by IR, NMR, and CD spectroscopy and the experimental observations were corroborated by DFT studies in solution. The most stable conformers of the homochiral peptides adopted the interstrand hydrogen-bond patterns, realized through ten- and thirteen-membered rings. The common feature of the most stable conformers of the heterochiral peptides was the adoption of the turn-like structures that feature the simultaneous intra- (seven-membered) and interstrand (sixteen-membered) hydrogen-bonded rings. An exchange of two N-terminal groups had a somewhat larger influence on the distribution of the hydrogen-bond patterns in homochiral than in heterochiral derivatives. The homochiral peptides that contain pyridine moieties as metal coordination sites formed 1:1 complexes with divalent metal ions, which included Zn2+ , Cd2+ , Cu2+ and Fe2+ .

Magnetostructural Characterization of Oxalamide Dihalo-Bridged Copper Dimers: Intra- and Interdimer Interactions Studied by Single-Crystal Electron Spin Resonance Spectroscopy.

Detailed single-crystal electron spin resonance (ESR) analysis of oxalamide complexes with halogen-bridged copper dimers, supported by X-ray, magnetic susceptibility, and powder ESR studies, is reported. Four complexes with two different ligands are synthesized: [CuLA (µ-X)]2 and [CuLV (µ-X)]2 , for which LA =N-(l-alanine methyl ester)-N'-[(2-pyridine-2-yl)methyl]oxalamide and LV =N-(l-valine methyl ester)-N'-[(2-pyridine-2-yl)methyl]oxalamide, for which X=Cl or Br. X-ray analysis shows that the geometry at each copper(II) ion is square pyramidal, whereas two pyramids share one base-to-apex edge with parallel basal planes. The complexes are linked by hydrogen bonds into infinite chains and are further linked into a 3D network. Susceptibility measurements show that the copper centers in the dimers are weakly antiferromagnetically coupled (|J|≈1-2 cm-1 ). From powder ESR spectroscopy, the g values and dx2-y2 orbital as the ground state of the unpaired electron are determined. The complexes show unusual anisotropic splitting and merging of the ESR lines if their single crystals rotate in a magnetic field. The observation of this partially resolved intradimer dipolar splitting enables estimation of the weak interdimer exchange interaction parameter |J'|≈0.001 cm-1 .

An axial chirality and disorder of positional isomers in a crystal of highly cytotoxic 3-acetyl-1,3-bis(2-chloro-4-nitrophenyl)-1E-triazene.

Biologically active 4-nitro-substituted 1,3-diaryltriazene, a chemical analogue of 1,3-bis(4'-amidinophenyl)-triazene-berenil®, belongs to the novel, chemically modified class of potent antitumor agents. Its structural characterization by X-ray analysis and 1H NMR spectroscopy is performed to determine molecular overall conformation in view of its possible interaction to DNA.

A 3D oxalate-based network as a precursor for the CoMn2O4 spinel: synthesis and structural and magnetic studies.

A novel heterometallic oxalate-based compound of the formula {[Co(bpy)3][Mn2(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) was synthesized and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction (XRD), and magnetization measurement. The molecular structure of 1 is made of a three-dimensional (3D) anionic network, [Mn2(C2O4)3]n(2n-), and tris-chelated cations [Co(bpy)3](2+) occupying the vacancies of the framework. Splitting between the zero-field-cooled (ZFC) and field-cooled (FC) branches of susceptibility below the small peak at 13 K indicates magnetic ordering. Compound 1 was used as a single-source precursor for the formation of the mixed-metal oxide CoMn2O4. This conversion via thermal decomposition was explored by thermal analysis (TGA and DTA), IR spectroscopy, powder XRD, and magnetic susceptibility measurement. From refined structural parameters, it could be seen that the spinel obtained by the thermal treatment of 1 at 800 °C is characterized by the inversion parameter δ = 21%, and therefore the structural formula at room temperature can be written as (tet)[Co(0.79)Mn(0.21)](oct)[Co(0.105)Mn(0.895)]2O4. The temperature dependence of magnetization for CoMn2O4 points to at least three magnetic phases: the ferrimagnetic state is observed below 83 K, and up to 180 K blocking of the magnetic moments of nanocrystallites of 31 nm appears, transforming to paramagnetic-like behavior above 180 K. Microstructural characterization of the CoMn2O4 sample was carried out by means of XRD line-broadening analysis.

Nitranilic acid hexahydrate, a novel benchmark system of the Zundel cation in an intrinsically asymmetric environment: spectroscopic features and hydrogen bond dynamics characterised by experimental and theoretical methods.

Nitranilic acid (2,5-dihydroxy-3,6-dinitro-2,5-cyclohexadiene-1,4-dione) as a strong dibasic acid in acidic aqueous media creates the Zundel cation, H5O2(+). The structural unit in a crystal comprises (H5O2)2(+) (2,5-dihydroxy-3,6-dinitro-1,4-benzoquinonate)(2-) dihydrate where the Zundel cation reveals no symmetry, being an ideal case for studying proton dynamics and its stability. The Zundel cation and proton transfer dynamics are studied by variable-temperature X-ray diffraction, IR and solid-state NMR spectroscopy, and various quantum chemical methods, including periodic DFT calculations, ab initio molecular dynamics simulation, and quantization of nuclear motion along three fully coupled internal coordinates. The Zundel cation features a short H-bond with the O···O distance of 2.433(2) Å with an asymmetric placement of hydrogen. The proton potential is of a single well type and, due to the non-symmetric surroundings, of asymmetric shape. The formation of the Zundel cation is facilitated by the electronegative NO2 groups. The employed spectroscopic techniques supported by calculations confirm the presence of a short H-bond with a complex proton dynamics.

Conjugates of 1'-aminoferrocene-1-carboxylic acid and proline: synthesis, conformational analysis and biological evaluation.

Our previous studies showed that alteration of dipeptides Y-Fca-Ala-OMe (III) into Y-Ala-Fca-OMe (IV) (Y=Ac, Boc; Fca=1'-aminoferrocene-1-carboxylic acid) significantly influenced their conformational space. The novel bioconjugates Y-Fca-Pro-OMe (1, Y=Ac; 2, Y=Boc) and Y-Pro-Fca-OMe (3, Y=Boc; 4, Y=Ac) have been prepared in order to investigate the influence of proline, a well-known turn-inducer, on the conformational properties of small organometallic peptides with an exchanged constituent amino acid sequences. For this purpose, peptides 1-4 were subjected to detailed spectroscopic analysis (IR, NMR, CD spectroscopy) in solution. The conformation of peptide 3 in the solid state was determined. Furthermore, the ability of the prepared conjugates to inhibit the growth of estrogen receptor-responsive MCF-7 mammary carcinoma cells and HeLa cervical carcinoma cells was tested.

Base-pairing of uracil and 2,6-diaminopurine: from cocrystals to photoreactivity.

We show that the non-canonical nucleobase 2,6-diaminopurine (D) spontaneously base pairs with uracil (U) in water and the solid state without the need to be attached to the ribose-phosphate backbone. Depending on the reaction conditions, D and U assemble in thermodynamically stable hydrated and anhydrated D-U base-paired cocrystals. Under UV irradiation, an aqueous solution of D-U base-pair undergoes photochemical degradation, while a pure aqueous solution of U does not. Our simulations suggest that D may trigger the U photodimerization and show that complementary base-pairing modifies the photochemical properties of nucleobases, which might have implications for prebiotic chemistry.