Spectroscopic, Thermal, Microbiological, and Antioxidant Study of Alkali Metal 2-Hydroxyphenylacetates.
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ABSTRACT:
SUBMITTER: Samsonowicz M
PROVIDER: S-EPMC8708765 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K2picene single crystal, while only parts of the crystal are doped and transformed into K2picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping.
| S-EPMC5956060 | biostudies-literature
Project description:Lithium, sodium, potassium, rubidium and caesium salts of 5-O-caffeoylquinic acid (chlorogenic acid, 5-CQA) were synthesized and described by FT-IR (infrared spectroscopy), FT-Raman (Raman spectroscopy), UV (UV absorption spectroscopy), ¹H (400.15 MHz), 13C (100.63 MHz) NMR (nuclear magnetic resonance spectroscopy). The quantum-chemical calculations at the B3LYP/6-311++G** level were done in order to obtain the optimal structures, IR spectra, NBO (natural bond orbital) atomic charges, HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) orbitals and chemical reactivity parameters for 5-CQA and Li, Na and K 5-CQAs (chlorogenates). The DPPH (?, ?-diphenyl-?-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assays were used for the preliminary estimation of the antioxidant properties of alkali metal chlorogenates and chlorogenic acid. In the DPPH assay the EC50 parameter were equal to 7.39 ?M for 5-CQA and was in the range of 4.50-5.89 ?M for salts. The FRAP values for two different concentrations (5 and 2.5 ?M) of the studied compounds were respectively 114.22 and 72.53 ?M Fe2+ for 5-CQA, whereas for salts they were 106.92-141.13 and 78.93-132.00 ?M Fe2+. The 5-CQA and its alkali metal salts possess higher antioxidant properties than commonly applied antioxidants (BHA, BHT, l-ascorbic acid). The pro-oxidant action of these compounds on trolox oxidation was studied in the range of their concentration 0.05-0.35 ?M. The lipophilicity (logkw) of chlorogenates and chlorogenic acid was determined by RP-HPLC (reverse phase-high performance liquid chromatography) using five different columns (C8, PHE (phenyl), CN (cyano), C18, IAM (immobilized artificial membrane)). The compounds were screened for their in vitro antibacterial activity against E. coli, Bacillus sp., Staphylococcus sp., Streptococcus pyogenes and antifungal activity against Candida sp. The 5-CQA possessed lower antibacterial (minimal inhibitory concentration, MIC = 7.06 mM) and antifungal (MIC = 14.11 mM) properties than its alkali metal salts (MIC values: 6.46-2.63 mM and 12.91-5.27mM, respectively). The synthesized chlorogenates possessed better antioxidant, lipophilic, antimicrobial as well as lower pro-oxidant properties than the ligand alone. Moreover, a systematic change of the activity of alkali metal salts along the series Li?Cs suggests that there are correlations between the studied biological properties. The type of metal cation in the carboxylate group of chlorogenate is crucial for the activity of studied compounds.
| S-EPMC5855685 | biostudies-other
Project description:The molecular structure of alkali metal rosmarinates was studied in comparison to rosmarinic acid using FT-IR, FT-Raman, 1H and 13C NMR spectroscopy, as well as density functional theory (DFT) calculations. The B3LYP/6-311+G(d,p) method was used to calculate optimized geometrical structures of studied compounds, atomic charges, dipole moments, energies, as well as the wavenumbers and intensities of the bands in vibrational and NMR spectra. Theoretical parameters were compared to experimental data. Antioxidant activity was determined using two spectrophotometric methods: (i) Assessing the ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable radical and (ii) assay of antioxidant power of ferric ions reducing (FRAP). The linear correlations were found between HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) energy gap and the reducing power expressed as FRAP (R = 0.77) as well as between IC50 values (the ability of quenching DPPH radicals) and Δνas-s(COO) in IR spectra (differences between asymmetric and symmetric stretching vibrations bands) (R = 0.99). Photochemical properties of studied compounds were also evaluated. The influence of alkali metal on the electronic system of the rosmarinic acid molecule was discussed.
| S-EPMC6680818 | biostudies-literature
Project description:Advancing the understanding of using alkali-metal alkoxides as additives to organomagnesium reagents in Mg-Br exchange reactions, a homologous series of mixed-ligand alkyl/alkoxide alkali-metal magnesiates [MMg(CH2 SiMe3 )2 (dmem)]2 [dmem=2-{[2-(dimethylamino)ethyl]methylamino} ethoxide; M=Li, 1; Na, 2; (THF)K, 3] has been prepared. Structural and spectroscopic studies have established the constitutions of these heteroleptic/heterometallic species, which are retained in arene solution. Evaluation of their reactivity towards 2-bromoanisole has uncovered a marked alkali-metal effect with potassium magnesiate 3 being the most efficient of the three ate reagents. Studies probing the constitution of the exchange product from this reaction suggest that the putative [KMgAr2 (dmem)]2 (Ar=o-OMe-C6 H4 ) intermediate undergoes redistribution into its single metal components [KAr]n and [MgAr(dmem)]2 (5). This process can be circumvented by using a different potassium alkoxide containing an aliphatic chain such as KOR' (R'=2-ethylhexyl) which undergoes co-complexation with Mg(CH2 SiMe3 ) to give [KMg(CH2 SiMe3 )2 (OR')]2 (7). This ate, in turn, reacts quantitatively with 2-bromoanisole furnishing [KMgAr2 (OR')]2 (9) which is stable in solution as a bimetallic compound. Collectively this work highlights the complexity of these alkali-metal mediated Mg-Br exchange reactions, where each reaction component can have a profound effect not only on the success of the reaction; but also the stability of the final metalated intermediates prior to their electrophilic interception.
| S-EPMC9306829 | biostudies-literature
Project description:Synergic combinations of alkali-metal hydrocarbyl/amide reagents were used to synthesise saturated N-heterocyclic carbene (NHC) ligands tethered to a fluorenide anion through deprotonation of a spirocyclic precursor, whereas conventional bases were not successful. The Li2 derivatives displayed a bridging amide between two Li atoms within the fluorenide-NHC pocket, whereas the Na2 and K2 analogues displayed extended solid-state structures with the fluorenide-NHC ligand chelating one alkali metal centre.
| S-EPMC6492165 | biostudies-literature
Project description:Alkali metal (AM) intercalation between graphene layers holds promise for electronic manipulation and energy storage, yet the underlying mechanism remains challenging to fully comprehend despite extensive research. In this study, we employ low-voltage scanning transmission electron microscopy (LV-STEM) to visualize the atomic structure of intercalated AMs (potassium, rubidium, and cesium) in bilayer graphene (BLG). Our findings reveal that the intercalated AMs adopt bilayer structures with hcp stacking, and specifically a C6M2C6 composition. These structures closely resemble the bilayer form of fcc (111) structure observed in AMs under high-pressure conditions. A negative charge transferred from bilayer AMs to graphene layers of approximately 1~1.5×1014 e-/cm-2 was determined by electron energy loss spectroscopy (EELS), Raman, and electrical transport. The bilayer AM is stable in BLG and graphite superficial layers but absent in the graphite interior, primarily dominated by single-layer AM intercalation. This hints at enhancing AM intercalation capacity by thinning the graphite material.
| S-EPMC11258350 | biostudies-literature
Project description:The incorporation of heavy alkali metals into substrates is both challenging and essential for many reactions. Here, we report the formation of THF-solvated alkali metal benzyl compounds [PhCH2 M ⋅ (thf)n ] (M=Na, Rb, Cs). The synthesis was carried out by deprotonation of toluene with the bimetallic mixture n-butyllithium/alkali metal tert-butoxide and selective crystallization from THF of the defined benzyl compounds. Insights into the molecular structure in the solid as well as in solution state are gained by single crystal X-ray experiments and NMR spectroscopic studies. The compounds could be successfully used as alkali metal mediating reagents. The example of caesium showed the convenient use by deprotonating acidic C-H as well as N-H compounds to gain insight into the aminometalation using these reagents.
| S-EPMC9298144 | biostudies-literature
Project description:As part of an educational exercise designed to introduce school students to the technique of single-crystal X-ray diffraction and enhance their understanding of primary and secondary bonding, a group of nine secondary school students was given the opportunity to prepare new compounds and to solve and refine data collected on the crystalline materials they had prepared. Their investigation of the alkali metal salts of 4-hydroxybenzoic acid (H2hba) yielded nine new compounds and their structures are described in this article. Whilst the salts might be expected to have similar atomic arrangements, there are significant differences in their structures. Although H2hba is a relatively simple organic molecule, it displays remarkable coordinative flexibility, forming ionic solids containing the uncharged molecule, the monoanion Hhba- or the dianion hba2-. A common feature of the structures is their layered arrangement: alternating hydrophilic layers made up of closely packed metal-oxygen polyhedra separated by the hydrophobic component of the hydroxybenzoate linking units. Close packing of these units seems to be a dominant influence in determining the overall structure. The hydroxybenzoate units are usually both parallel and antiparallel with their immediate neighbours, with packing that can be edge-to-face, face-to-face or a mixture of the two. Hydrogen bonding plays a key role in the structure of most compounds and a short strong hydrogen bond (SSHB) is observed in two of the networks. The compounds of 4-hydroxybenzoic acid, C7H6O3, described here are: poly[di-μ-aqua-μ-4-oxidobenzoato-dilithium], [Li2(C7H4O3)(H2O)2]n, 1, poly[triaqua-μ-4-oxidobenzoato-dilithium], [Li2(C7H4O3)(H2O)3]n, 2, poly[μ-4-hydroxybenzoato-lithium], [Li(C7H5O3)]n, 3, catena-poly[4-hydroxybenzoate [[diaquasodium]-di-μ-aqua]], {[Na(H2O)4](C7H5O3)}n, 4, poly[di-μ-aqua-aqua-μ-4-hydroxybenzoato-potassium], [K(C7H5O3)(H2O)3]n, 5, poly[μ-aqua-μ-4-hydroxybenzoato-potassium], [K(C7H5O3)(H2O)]n, 6, poly[aqua-μ-4-hydroxybenzoato-rubidium], [Rb(C7H5O3)(H2O)]n, 7, poly[aqua-μ-4-hydroxybenzoato-caesium], [Cs(C7H5O3)(H2O)]n, 8, poly[[μ-aqua-aqua(μ-4-hydroxybenzoato)(4-hydroxybenzoic acid)sodium] monohydrate], {[Na(C7H5O3)(C7H6O3)(H2O)2]·H2O}n, 9, poly[[(μ-4-hydroxybenzoato)(μ-4-hydroxybenzoic acid)rubidium] monohydrate], {[K(C7H5O3)(C7H6O3)]·H2O}n, 10, and poly[[(μ-4-hydroxybenzoato)(μ-4-hydroxybenzoic acid)rubidium] monohydrate], {[Rb(C7H5O3)(C7H6O3)]·H2O}n, 11.
| S-EPMC8254528 | biostudies-literature
Project description:Bulky amido ligands are precious in s-block chemistry, since they can implant complementary strong basic and weak nucleophilic properties within compounds. Recent work has shown the pivotal importance of the base structure with enhancement of basicity and extraordinary regioselectivities possible for cyclic alkali metal magnesiates containing mixed n-butyl/amido ligand sets. This work advances alkali metal and alkali metal magnesiate chemistry of the bulky arylsilyl amido ligand [N(SiMe3 )(Dipp)]- (Dipp=2,6-iPr2 -C6 H3 ). Infinite chain structures of the parent sodium and potassium amides are disclosed, adding to the few known crystallographically characterised unsolvated s-block metal amides. Solvation by N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) or N,N,N',N'-tetramethylethylenediamine (TMEDA) gives molecular variants of the lithium and sodium amides; whereas for potassium, PMDETA gives a molecular structure, TMEDA affords a novel, hemi-solvated infinite chain. Crystal structures of the first magnesiate examples of this amide in [MMg{N(SiMe3 )(Dipp)}2 (μ-nBu)]∞ (M=Na or K) are also revealed, though these breakdown to their homometallic components in donor solvents as revealed through NMR and DOSY studies.
| S-EPMC5096043 | biostudies-literature
Project description:A 3-unit cellulose model molecule was built and optimized using DFT B3LYP/6-31G(d,p). The electronic properties of the optimized structure of cellulose were investigated in terms of total dipole moment (TDM), HOMO-LUMO band gap (ΔE), and molecular electrostatic potential (MESP). Cellulose demonstrated a TDM of 9.106 Debye and ΔE of 7.647 eV. The hydrogen atom of the hydroxyl group of the CH2OH group of each cellulose unit was replaced by an alkali metal atom (X) such that the 3-unit cellulose once had 1X atom, then 2X, then 3X atoms, where X = Li, Na or K, both without and with 2, 4 and 6 water molecules (W), respectively, to study also the effect of hydration. Without hydration, the values of TDM decreased for all of the proposed interaction, but increased with hydration, while ΔE decreased in all interactions, confirming that interaction cellulose-alkali metal interaction, especially with hydration, resulted in more reactive structures. Mapping of HOMO-LUMO and MESP indicated significant change in the electron density distribution around cellulose under the effect of interaction with the alkali metals, both with and without hydration. The plots of projected density of states also clearly demonstrated the contribution of each alkali metal as well as water in the molecular orbitals, reflecting their effect on the electronic properties of cellulose and cellulose-alkali metals composites. The theoretical calculations were experimentally verified using FTIR and FT-Raman spectroscopy.
| S-EPMC10709645 | biostudies-literature