Organic electrochemistry is currently experiencing an era of renaissance, which is closely related to the possibility of carrying out organic transformations under mild conditions, with high selectivity, high yields, and without the use of toxic solvents. Combination of organic electrochemistry with alternative approaches, such as photo-chemistry was found to have great potential due to induced synergy effects. In this work, we propose for the first time utilization of plasmon triggering of enhanced and regio-controlled organic chemical transformation performed in photoelectrochemical regime. The advantages of the proposed route is demonstrated in the model amination reaction with formation of C-N bond between pyrazole and substituted benzene derivatives. Amination was performed in photo-electrochemical mode on the surface of plasmon active Au@Pt electrode with attention focused on the impact of plasmon triggering on the reaction efficiency and regio-selectivity. The ability to enhance the reaction rate significantly and to tune products regio-selectivity is demonstrated. We also performed density functional theory calculations to inquire about the reaction mechanism and potentially explain the plasmon contribution to electrochemical reaction rate and regioselectivity.
- Klíčová slova
- C−H activation, amination, organic electrocatalysis, plasmon-assisted chemistry, regio-selectivity,
- Publikační typ
- časopisecké články MeSH
Iron-containing zeolite-based catalysts play a pivotal role in environmental processes aimed at mitigating the release of harmful greenhouse gases, such as nitrous oxide (N2O) and methane (CH4). Despite the rich iron chemistry in zeolites, only a fraction of iron species that exhibit an open coordination sphere and possess the ability for electron transfer are responsible for activating reagents. In addition, the splitting of molecular oxygen is facilitated by bare iron cations embedded in zeolitic matrices. Mössbauer spectroscopy is the ideal tool for investigating the valency and geometry of iron species in zeolites because it leaves no iron forms silent and provides insights into in-situ processes. This review is dedicated to the utilization of Mössbauer spectroscopy to elucidate the nature of the extra-framework iron centers in ferrierite (FER), beta-structured (*BEA), and ZSM-5 zeolite (MFI) zeolites, which are active in N2O decomposition and CH4 oxidation through using the active oxygen derived from N2O and O2. In this work, a structured summary of the Mössbauer parameters established over the last two decades is presented, characterizing the specific iron active centers and intermediates formed upon iron's interaction with N2O/O2 and CH4. Additionally, the impact of preparation methods, iron loading, and the long-term stability on iron speciation and its redox behavior under reaction conditions is discussed.
- Klíčová slova
- Mössbauer spectroscopy, N2O decomposition, iron sites, methane, zeolites,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Herein, we report the development of a macromolecular multifunctional imaging tool for biological investigations, which is comprised of an N-(2-hydroxypropyl)methacrylamide backbone, iridium-based luminescent probe, glutamate carboxypeptidase II (GCPII) targeting ligand, and biotin affinity tag. The iridium luminophore is a tris-cyclometalated complex based on [Ir(ppy)3] with one of its 2-phenylpyridine ligands functionalized to allow conjugation. Synthesized macromolecular probes differed in the structure of the polymer and content of the iridium complex. The applicability of the developed imaging tools has been tested in flow cytometry (FACS) based assay, laser confocal microscopy, and fluorescence lifetime imaging microscopy (FLIM). The FACS analysis has shown that the targeted iBodies containing the iridium luminophore exhibit selective labelling of GCPII expressing cells. This observation was also confirmed in the imaging experiments with laser confocal microscopy. The FLIM experiment has shown that the iBodies with the iridium label exhibit a lifetime greater than 100 ns, which distinguishes them from typically used systems labelled with organic fluorophores exhibiting short fluorescence lifetimes. The results of this investigation indicate that the system exhibits interesting properties, which supports the development of additional biological tools utilizing the key components (iridium complexes, iBody concept), primarily focusing on the longer lifetime of the iridium emitter.
- Klíčová slova
- HPMA, iBody, imaging, iridium complex,
- MeSH
- fluorescenční barviva chemie MeSH
- fluorescenční mikroskopie metody MeSH
- iridium * chemie MeSH
- konfokální mikroskopie * MeSH
- lidé MeSH
- optické zobrazování metody MeSH
- polymery * chemie MeSH
- průtoková cytometrie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The coordination capability of two N,C,N pincer coordinated stibinidenes, i. e. bis(imino)- [2,6-(DippN=CH)2C6H3]Sb (1) or imino-amino- [2-(DippN=CH)-6-(DippNHCH2)C6H3]Sb (2) toward palladium(II) and platinum(II) centers was examined. In the course of this study, seven new square-planar bis(stibinidene) complexes were synthesized and characterized by NMR, IR, Raman, UV-vis spectroscopy and single crystal (sc)-X-ray diffraction analysis. In all cases, both stibinidene ligands 1 or 2 adopt trans positions, but differ significantly in the torsion angle describing mutual orientation of aromatic rings of the stibinidenes along the Sb-Pd/Pt-Sb axes. Furthermore, majority of complexes form isomers in solution most probably due to a hindered rotation around Sb-Pd/Pt bonds caused by bulkiness of 1 and 2. This phenomenon also seems to be influenced by the absence/presence of a pendant -CH2NH- group in 1/2 that is able to form intramolecular hydrogen bonds with the adjacent chlorine atom(s) attached to the metal centers. The whole problem was subjected to a theoretical study focusing on the role of hydrogen bonds in structure architecture of the complexes. To describe the UV-vis spectra of these highly coloured complexes, TD-DFT calculations were employed. These outline differences between the stibinidene ligands, the transition metals as well as between the charge of the complexes (neutral or anionic).
- Klíčová slova
- TD-DFT, hydrogen-bond, palladium, platinum, stibinidene,
- Publikační typ
- časopisecké články MeSH
A set of graphitic carbon nitride samples was prepared using a straightforward experimental procedure without templates and any subsequent treatments. The materials were studied in-depth using a range of physical and chemical methods such as X-ray diffraction, FTIR spectroscopy, elemental analysis (CHN), nitrogen physisorption, SEM, XPS, TPD CO2. The resulting g-C3N4 was shown to be highly efficient in carboxymethylation of cinnamyl alcohol with dimethyl carbonate yielding up to ca. 82 % of the desired cinnamyl methyl carbonate. In the studied conditions, an increase in the surface N atomic content leads to an increase in selectivity towards the desired carbonate, while a higher surface O content was beneficial for side products. Metal-free graphitic carbon nitride was shown to be one of the most productive (ca. 2 mol/h kgcat) in the investigated reaction among studied heterogeneous catalysts.
- Klíčová slova
- carbonate esters, carboxymethylation, graphitic carbon nitride, heterogeneous catalysis, metal-free catalysts,
- Publikační typ
- časopisecké články MeSH
2,9- and 2,10-diphenylpentacene were synthesized by direct C-H borylation of ketal-protected pentacene, followed by halodeboronation, resolution of the dihalo isomers, Suzuki arylation, cleavage of the ketals and decarbonylation in the solid state. They were studied as main active components in organic field effect transistors (OFETs). Diphenyl substitution of pentacene affects the unit cell dimensions only slightly, preserving a face to edge molecular packing in the first layers of thin films evaporated on SiO2 substrates. Both isomers self-assemble into nanoribbons during the thin film growth upon vapor deposition. The similarity between the surface induced phases of the 2,9-isomer and unsubstituted pentacene leads to similar 4-probe hole mobilities, i. e. 0.13 cm2 V-1 s-1 for the former. Whereas 2,9-disubstitution thus does essentially preserve the thin film characteristics of unsubstituted pentacene, 2,10-disubstitution is detrimental to the molecular ordering in the thin films and therefore to the field effect mobility which is only 0.07 cm2 V-1 s-1. The known strong enhancement of field effect mobility observed upon diphenyl substitution of anthracene can thus not be emulated analogously with pentacene.
- Klíčová slova
- acenes, charge mobility, nanostructures, organic electronics, organic field effect transistors,
- Publikační typ
- časopisecké články MeSH
This work reports a biomimetic synthesis of polyarylated fluorene derivatives. The molecules are formed via intramolecular electrophilic aromatic substitution, resembling a cyclization leading towards the natural selaginpulvilins from selaginellins. The scope of the reaction was investigated, and the products were obtained in 60-95 % yields. Some of the compounds decompose to a stable radical. We investigated the nature and the origin of the radical using experimental methods, including EPR or electrochemical measurements, as well as theoretical methods, such as DFT calculations. Based on our observations, we hypothesize, that phenoxy radicals are formed in the first instance, which however undergo internal rearrangement to thermodynamically more stable carbon-centered radicals. The preliminary data also show the cytotoxic properties of some of the molecules.
- Klíčová slova
- biomimetic synthesis, cytotoxicity, radicals, selaginellacea polyphenols, spin density distribution,
- Publikační typ
- časopisecké články MeSH
In this study, Ru complexes [(η6-p-cymene)RuX(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O))] (3: X=Cl; 4: X=I) were prepared with N-bound 2-pyridonato ligand by thermal base-free MeX elimination from ionic N,N-chelated Ru complexes [(η6-p-cymene)RuX(κ2-L1)](X) (1: X=Cl; 2: X=I; L1={2-[(2,6-iPr2-C6H3)N=CH]-6-(OMe)C5H3N}). The Ru complex 3 was used as O-donor for Lewis (LA) or Brönsted acids. The reactions of 3 with SnCl2, Ph3SnCl, ZnCl2 or HCl provided [(η6-p-cymene)Ru(SnCl3)(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O→SnCl2)] (6), [(η6-p-cymene)RuCl(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O→SnPh3Cl)] (7), and [(η6-p-cymene)RuCl(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(O→)]2(μ-ZnCl2) (8) and [(η6-p-cymene)RuCl(2-{(2,6-iPr2-C6H3)N=CH}-C5H3N-6-(OH)}](Cl) (9). The easy conversion of the 2-pyridonato ligand in 3 to its 2-hydroxypyridine in 9 evoked testing of 3 and 4 as potential catalysts in base-free transfer-hydrogenation of ketones.
- Klíčová slova
- catalysis, coordination chemistry, pyridonato ligands, ruthenium, transfer-hydrogenation,
- Publikační typ
- časopisecké články MeSH
Covalent adducts of flavin cofactors with nucleophiles play an important role in non-canonical function of flavoenzymes as well as in flavin-based catalysis. Herein, the interaction of flavin derivatives including substituted flavins (isoalloxazines), 1,10-ethylene-bridged flavinium salts, and non-substituted alloxazine and deazaflavin with selected nucleophiles was investigated using an experimental and computational approach. Triphenylphosphine or trimethylphosphine, 1-nitroethan-1-ide, and methoxide were selected as representatives of neutral soft, anionic soft, and hard nucleophiles, respectively. The interactions were investigated using UV/Vis and 1 H NMR spectroscopy as well as by DFT calculations. The position of nucleophilic attack estimated using the calculated Gibbs free energy values was found to correspond with the experimental data, favouring the addition of phosphine and 1-nitroethan-1-ide into position N(5) and methoxide into position C(10a) of 1,10-ethylene-bridged flavinium salts. The calculated Gibbs free energy values were found to correlate with the experimental redox potentials of the flavin derivatives tested. These findings can be utilized as valuable tools for the design of artificial flavin-based catalytic systems or investigating the mechanism of flavoenzymes.
- Klíčová slova
- Biomimetic catalysis, Cofactors, Computational chemistry, Electrochemistry, Nucleophiles, Spectroscopy,
- Publikační typ
- časopisecké články MeSH
Galectins, a class of carbohydrate-binding proteins, play a crucial role in various physiological and disease processes. Therefore, the identification of ligands that efficiently bind these proteins could potentially lead to the development of new therapeutic compounds. In this study, we present a method that involves screening synthetic click glycopeptide libraries to identify lectin-binding ligands with low micromolar affinity. Our methodology, initially optimized using Concanavalin A, was subsequently applied to identify binders for the therapeutically relevant galectin 1. Binding affinities were assessed using various methods and showed that the selected glycopeptides exhibited enhanced binding potency to the target lectins compared to the starting sugar moieties. This approach offers an alternative means of discovering galectin-binding ligands as well as other carbohydrate-binding proteins, which are considered important therapeutic targets.
- Klíčová slova
- click chemistry, glycopeptide libraries, lectins, split-and-mix, sugars,
- Publikační typ
- časopisecké články MeSH
