Atomic interface regulation that can efficiently optimize the performance of single‐atom catalysts (SACs) is a worthwhile research topic. The challenge lies in deeply understanding the ...structure–properties correlation based on control of the coordination chemistry of individual atoms. Herein, a new kind of W SACs with oxygen and nitrogen coordination (W‐NO/NC) and a high metal loading over 10 wt% is facilely prepared by introducing an oxygen‐bridged WO4 tetrahedron. The local structure and coordination environment of the W SACs are confirmed by high‐angle annular dark‐field scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, and extended X‐ray absorption fine structure. The catalyst shows excellent selectivity and activity for the electrochemical nitrogen reduction reaction (NRR). Density functional theory calculation reveals that unique electronic structures of the N and O dual‐coordinated W sites optimize the binding energy of the NRR intermediate, resulting in facilitating the electrocatalytic NRR. This work opens an avenue toward exploring the correlation between coordination structure and properties.
A new kind of W single‐atom catalysts (SACs) with N and O dual‐coordination (W‐oxygen and nitrogen coordination NO/NC) is prepared to achieve excellent electrochemical nitrogen reduction reaction (NRR) performance. The unique electronic structures optimize the binding energy of NRR intermediate, resulting in facilitating the selectivity and activity of NRR. This opens an avenue toward exploring the correlation between coordination structure and properties.
Preparation, characterization, and catalytic properties of bimetallic coordination polymer constructed from 2‐aminoterephthalic acid as linker, zinc cations as node, and cis‐dioxo molybdenum units as ...catalytic active sites are reported via two pathways. Molybdenum centers were placed in N,O positions created by condensation reaction of 2‐aminoterephthalic acid with salicylaldehyde while zinc cations coordinated via carboxylic acid groups of linker to achieve infinite chains of metalo‐ligand. The obtained coordination polymer was fully characterized and its catalytic properties in the epoxidation of olefins with tert‐butyl hydroperoxide (TBHP) described. In comparison with previously reported heterogenized molybdenum catalysts, this new coordination polymer exhibited good conversion as well as high selectivity in the epoxidation of olefins. The catalyst is stable under ambient conditions and could be reused as active catalyst for at least five times.
Two paths were used to heterogenize Schiff base molybdenum complex on infinite coordination polymer via coordination‐polymerization. Prepared zinc‐molybdenum based coordination polymer was used as efficient self‐supported catalyst for olefins epoxidation. Cyclooctene shows highest catalytic activity among olefins.
Alzheimer's disease (AD) is associated with the presence of amyloid plaques in the brain mainly comprised of aggregated forms of amyloid-β (Aβ). Molecules radiolabeled with technetium-99m that cross ...the blood-brain barrier (BBB) and selectively bind to Aβ plaques have the potential to assist in the diagnosis of AD using single-photon emission computed tomography imaging. In this work, three new tetradentate ligands of pyridyl, amide, amine and thiol donors, featuring a styrylpyridyl group that is known to interact with amyloid plaques, were prepared. The new ligands formed charge-neutral and lipophilic complexes with the Tc═O
and Re═O
motifs, and two rhenium complexes were characterized by X-ray crystallography. The rhenium(V) complexes interact with synthetic Aβ
and amyloid plaques on human brain tissue. Two of the new ligands were radiolabeled with
Tc using a kit-based approach, and their biodistribution in wild-type mice was evaluated. The presence of amide donors in the tetradentate ligand increased the stability of the respective Tc═O
complexes but reduced brain uptake. While the complexes were able to cross the BBB, the degree of uptake in the brain was not sufficient to justify further investigation of these complexes.
Hypoxic tumours are a major problem for cancer photodynamic therapy. Here, we show that photoredox catalysis can provide an oxygen-independent mechanism of action to combat this problem. We have ...designed a highly oxidative Ir(III) photocatalyst, Ir(ttpy)(pq)ClPF
(1PF
, where 'ttpy' represents 4'-(p-tolyl)-2,2':6',2''-terpyridine and 'pq' represents 3-phenylisoquinoline), which is phototoxic towards both normoxic and hypoxic cancer cells. Complex 1 photocatalytically oxidizes 1,4-dihydronicotinamide adenine dinucleotide (NADH)-an important coenzyme in living cells-generating NAD
radicals with a high turnover frequency in biological media. Moreover, complex 1 and NADH synergistically photoreduce cytochrome c under hypoxia. Density functional theory calculations reveal π stacking in adducts of complex 1 and NADH, facilitating photoinduced single-electron transfer. In cancer cells, complex 1 localizes in mitochondria and disrupts electron transport via NADH photocatalysis. On light irradiation, complex 1 induces NADH depletion, intracellular redox imbalance and immunogenic apoptotic cancer cell death. This photocatalytic redox imbalance strategy offers a new approach for efficient cancer phototherapy.
The pace of progress in biomedical research directly depends on techniques that enable the quantitative interrogation of interactions between proteins and other biopolymers, or with their ...small-molecule ligands. Time-resolved Förster resonance energy transfer (TR-FRET) assay platforms offer high sensitivity and specificity. However, the paucity of accessible and biocompatible luminescent lanthanide complexes, which are essential reagents for TR-FRET-based approaches, and their poor cellular permeability have limited broader adaptation of TR-FRET beyond homogeneous and extracellular assay applications. Here, we report the development of CoraFluors, a new class of macrotricyclic terbium complexes, which are synthetically readily accessible, stable in biological media and exhibit photophysical and physicochemical properties that are desirable for biological studies. We validate the performance of CoraFluors in cell-free systems, identify cell-permeable analogs and demonstrate their utility in the quantitative domain-selective characterization of Keap1 ligands, as well as in isoform-selective target engagement profiling of HDAC1 inhibitors in live cells.
Abstract
The electrochemical conversion of CO
2
to methane provides a means to store intermittent renewable electricity in the form of a carbon-neutral hydrocarbon fuel that benefits from an ...established global distribution network. The stability and selectivity of reported approaches reside below technoeconomic-related requirements. Membrane electrode assembly-based reactors offer a known path to stability; however, highly alkaline conditions on the cathode favour C-C coupling and multi-carbon products. In computational studies herein, we find that copper in a low coordination number favours methane even under highly alkaline conditions. Experimentally, we develop a carbon nanoparticle moderator strategy that confines a copper-complex catalyst when employed in a membrane electrode assembly. In-situ XAS measurements confirm that increased carbon nanoparticle loadings can reduce the metallic copper coordination number. At a copper coordination number of 4.2 we demonstrate a CO
2
-to-methane selectivity of 62%, a methane partial current density of 136 mA cm
−2
, and > 110 hours of stable operation.
A range of fluorescent alkynyl-naphthalimide fluorophores has been synthesized and their photophysical properties examined. The fluorescent ligands are based upon a 4-substituted 1,8-naphthalimide ...core and incorporate structural variations (at the 4-position) to tune the amphiphilic character: chloro (L1), 4-2-(2-aminoethoxy)ethanol (L2), 4-2-(2-methoxyethoxy)ethylamino (L3), piperidine (L4), morpholine (L5), 4-methylpiperidine (L6), and 4-piperidone ethylene ketal (L7) variants. The amino-substituted species (L2-L7) are fluorescent in the visible region at around 517-535 nm through a naphthalimide-localized intramolecular charge transfer (ICT), with appreciable Stokes' shifts of ca. 6500 cm(-1) and lifetimes up to 10.4 ns. Corresponding two-coordinate Au(I) complexes Au(L)(PPh3) were isolated, with X-ray structural studies revealing the expected coordination mode via the alkyne donor. The Au(I) complexes retain the visible fluorescence associated with the coordinated alkynyl-naphthalimide ligand. The ligands and complexes were investigated for their cytotoxicity across a range of cell lines (LOVO, MCF-7, A549, PC3, HEK) and their potential as cell imaging agents for HEK (human embryonic kidney) cells and Spironucleus vortens using confocal fluorescence microscopy. The images reveal that these fluorophores are highly compatible with fluorescence microscopy and show some clear intracellular localization patterns that are dependent upon the specific nature of the naphthalimide substituent.
We report the design, synthesis, and evaluation of a new type of non-precious-metal catalyst made from network polymers. 2,6-Diaminopyridine was selected as a building-block monomer for the formation ...of a nitrogen-rich network polymer that forms self-supporting spherical backbone structures and contains a high density of metal-coordination sites. A Co-/Fe-coordinating pyrolyzed polymer exhibited a high specific oxygen reduction activity with onset and half-wave potentials of 0.87 and 0.76 V vs RHE, respectively, in neutral media. There was no crossover effect of organics on its activity. The power output of a microbial fuel cell equipped with this catalyst on its cathode was more than double the output with a commercial 20 wt % Pt/C catalyst.
Two optically pure chiral binuclear copper(ii) complexes Cu2(μ-Cl)2L2·CH2Cl2 (1) and Cu2L4 (2) based on the natural product rosin derivative N-(5-dehydroabietyl-1,3,4-thiadiazole)-2-substituted ...pyridinecarboxamide (HL) were prepared, fully characterized and their biological activities were evaluated. The circular dichroism (CD), fluorescence spectroscopy, and DNA melting studies indicate that 1 and 2 interact with calf thymus DNA (CT DNA) via intercalation. It can be concluded that 1 and 2 have a strong affinity to bovine serum albumin (BSA) based on the fluorescence and CD spectral evidence. The MTT assay illustrates that the selective cytotoxic activity of 1 is better than that of HL, 2, cisplatin and oxaliplatin. The exposure of 1 to MCF-7 cells resulted in cell cycle arrest in the G1 phase, apoptosis, mitochondrial dysfunction and an elevated ROS level. The western blot analysis results indicate that 1 might induce apoptosis through intrinsic and extrinsic pathways, autophagy and DNA damage in MCF-7 cells. Furthermore, the down-regulated VEGFR2, MMP-2 and MMP-9 expression levels indicate that 1 should have the ability to resist metastasis and angiogenesis. Thus, based on the above described results 1 has high potential value for anticancer applications.
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