Manganese‐Catalysed Transfer Hydrogenation of Quinolines under Mild Conditions

Posted on 27 September 2023 by nXiaoxiao Chu, nGuoren Zhou, nMaofu Pang, nHongwu Zhangn

A PNP pincer manganese complex was applied as catalyst for transfer hydrogenation of quinolines with ammonia borane as hydrogen source. 1,2,3,4-Tetrahydroquinolines were obtained under mild conditions with good to excellent yields. 1,2-Dihydroquinolines were detected by ¹H NMR in the progress and isotopic labelling experiments were performed to determine the destination of ammonia-borane hydrogen atoms.

Abstract

Herein, an efficient methodology for the homogeneous manganese-catalysed transfer hydrogenation of N-heterocycles by using ammonia-borane as a hydrogen source under mild reaction conditions is reported. Good to excellent isolated yields are achieved by applying a PNP manganese pincer complex. In the reaction, 1,2-dihydroquinoline is detected as intermediate by NMR spectra analysis and deuterium labelling experiment. The catalytic reaction likely proceeded by an outer-sphere pathway based on the bifunctional pincer complex.

Diastereoselective Dearomatization of Chalcone‐Based Quinolinium Salts to Assemble Bridged Quinobenzazepine Polycycles

Posted on 27 September 2023 by

Herein, we designed and synthesized a range of multi-functional chalcone-based quinolinium salts and their synthetic application in the rapid and straightforward construction of oxa-bridged quinobenzazepine polycycles was successfully explored.

Abstract

Quinobenzazepines are useful in medicinal chemistry, but their synthesis is very challenging. Herein, we designed and synthesized a range of multi-functional chalcone-based quinolinium salts; their synthetic application in the rapid and straightforward construction of quinobenzazepines was successfully explored. A wide range of oxa-bridged quinobenzazepine polycycles were afforded serendipitously through a dearomative cascade reaction of our newly developed quinolinium salts and acetylacetone. This synthetic strategy features high bond- and ring-forming efficiency and complete regio- and diastereoselective control.

Amine Adsorbents Stability for Post‐Combustion CO2 Capture: Determination and Validation of Laboratory Degradation Rates in a Multi‐staged Fluidized Bed Pilot Plant

Posted on 27 September 2023 by

A robust method to determine degradation rates of an amine functionalized polystyrene adsorbent in a laboratory setup is developed and validated with a continuous multi-staged fluidized bed pilot plant. The very good agreement between experimental 1000-hour laboratory and 2200-hour pilot degradation showcases how small scale experiments can be extrapolated for scale-up and adsorbent screening.

Abstract

Alternative to current liquid amine technologies for post-combustion CO₂ capture, new technologies such as adsorbent-based processes are developed, wherein material lifetime and degradation is important. Herein a robust method to determine degradation rates in a laboratory setup is developed, which was validated with a continuous multi-staged fluidized bed pilot plant designed to capture 1 ton CO₂ per day. An amine functionalized polystyrene adsorbent showed very good agreement between the experimental 1000-hour laboratory degradation rates and 2200 hours of degradation in a pilot plant. This validates how laboratory experiments can be extrapolated for sorbent screening and for scale-up. Resulting, the oxidative degradation in the desorber at high temperatures (120 °C) and low O₂ concentrations (150 ppmv) is 3 times higher compared to the adsorber at low temperatures and high O₂ (56 °C, 7 vol %). Laboratory degradation experiments can hence be used to further optimize process operations to limit degradation or screen for potential new adsorbents.

Diaminocyclopentadienone Ruthenium Complex Catalyzed Alkylation of Indoles and Ketones with Primary Alcohols

Posted on 27 September 2023 by nSteffen Skowaisa, nEdgar Haakn

The borrowing hydrogen approach allows the direct utilization of non-activated alcohols as alkylating agents. A readily available, air and moisture stable ruthenium complex proves to be a particularly effective hydrogen autotransfer catalyst for the alkylation of various indoles or ketones with poorly reactive alcohols.

Abstract

A diaminocyclopentadienone ruthenium complex has proven to be a highly effective catalyst for the alkylation of indoles or ketones with poorly reactive alcohols. The catalyst is readily available, air and moisture stable and exhibits wide functional group tolerance. The environmentally benign procedure follows a borrowing hydrogen mechanism and requires no excess of either component. Various indoles and ketones are selectively monoalkylated in high yield.

A BODIPY‐Based Molecular Rotor in Giant Unilamellar Vesicles: A Case Study by Polarization‐Resolved Time‐Resolved Emission and Transient Absorption Spectroscopy

Posted on 27 September 2023 by

The ellipsoidal geometry of the BODIPY-Ar-chol molecule results in a tri-exponential decay of anisotropy dynamics. The molecule‘s radius along the y-axis is 6.3 Å and fluid volume displaced by rotation along the y-axis is 11983.9 Å³. The largest fluid volume displacement along the y-axis induces the largest rotational relaxation time of 440 ps. Rotational relaxation time along the x and z axes follow accordingly.

Abstract

BODIPY and BODIPY-derived systems are widely applied as fluorophores and as probes for viscosity detection in solvents and biological media. Their orientational and rotational dynamics in biological media are thus of vital mechanistic importance and extensively investigated. In this contribution, polarization-resolved confocal microscopy is used to determine the orientation of an amphiphilic BODIPY-cholesterol derivative in homogeneous giant unilamellar vesicles (GUV) made from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The BODIPY-moiety of the molecule is placed near the polar headgroups, and the cholesterol moiety is embedded in the membrane along the acyl chain of the lipids. The rotational relaxation of fluorophore is conventionally investigated by time-resolved emission anisotropy (TEA); and this method is also used here. However, TEA depends on the emission of the fluorophore and may not be useful to probe rotational dynamics of the non-emissive triplet states. Thus, we employ femtosecond transient absorption anisotropy (TAA), that relies on the absorption of the molecule to complement the studies of the amphiphilic BODIPY in DCM and GUV. The photoinduced anisotropy of the BODIPY molecule in DCM decays tri-exponentially, the decay components (sub-5 ps, 43 ps and 440 ps) of anisotropy are associated with the non-spherical shape of the BODIPY molecule. However, the anisotropy decay in homogenous GUVs follows a biexponential decay; which arises from the wobbling-in-a-cone motion of the non-spherical molecule in the high viscous lipid bilayer media. The observations for the BODIPY-chol molecule in the GUV environment by TAA will extend to the investigation of non-emissive molecules in cellular environment since GUV structure and size resembles the membrane of a biological cell.

Oxygen‐Mediated Surface Photoreactions: Exploring New Pathways for Sustainable Chemistry

Posted on 27 September 2023 by nIvano Alessandri, nIrene Vassalinin

Oxygen-mediated surface photoreactions are an extremely versatile tool for environmental remediation, recycling of critical raw materials and sustainable production of feedstocks. This Concept reviews recent works on this class of reaction, including examples of metal and polymer recovery and recycling from waste, metal-free oxidation of organic molecules and exploitation of persistent radicals for destroying pollutants and disinfection.

Abstract

This Concept analyses and reviews recent works that take advantage of oxygen-mediated surface photoreactions for addressing key issues in the fields of sustainable chemistry, circular production of feedstocks and environmental remediation. Examples of metal and polymer recovery and recycling from waste, metal-free oxidation of organic molecules and exploitation of persistent radicals for destroying pollutants and disinfection are discussed, highlighting common aspects, peculiarities, potential and limitations.

A Platinum(II) Boron‐dipyrromethene Complex for Cellular Imaging and Mitochondria‐targeted Photodynamic Therapy in Red Light

Posted on 27 September 2023 by

Acacplatin-RB, a cisplatin analog having acetylacetone-appended to boron-dipyrromethene (BODIPY) dye, exhibits mitochondrial localization and remarkable apoptotic red-light induced photodynamic therapy (PDT) forming singlet oxygen as reactive oxygen species. Moreover, this complex demonstrated decrease in mitochondrial membrane potential, disruption of microtubules under photoinduced conditions and anti-metastatic properties from wound-healing assay.

Abstract

Cisplatin-derived platinum(II) complexes [Pt(NH₃)₂(pacac)](NO₃) (1, DPP-Pt) and [Pt(NH₃)₂(Acac-RB)](NO₃) (2, Acacplatin-RB), where Hpacac is 1,3-diphenyl-1,3-propanedione and HAcac-RB is a red-light active distyryl-BODIPY-appended acetylacetone ligand, are prepared, characterized and their photodynamic therapy (PDT) activity studied (RB abbreviated for red-light BODIPY). Complex 2 displayed an intense absorption band at λ=652 nm (ϵ=7.3×10⁴ M⁻¹ cm⁻¹) and 601 nm (ϵ=3.1×10⁴ M⁻¹ cm⁻¹) in 1 : 1 DMSO-DPBS (Dulbecco's Phosphate Buffered Saline). Its emission profile includes a broad maximum at ~673 nm (λ_ex=630 nm). The fluorescence quantum yield (Φ_F) of HAcac-RB and 2 are 0.19 and 0.07, respectively. Dichlorodihydrofluorescein diacetate and 1,3-diphenylisobenzofuran assay of complex 2 indicated photogeneration of singlet oxygen (Φ_Δ: 0.36) as reactive oxygen species (ROS). Light irradiation caused only minor extent of ligand release forming chemo-active cisplatin analogue. The complex showed ~70–100 fold enhancement in cytotoxicity on light exposure in A549 lung cancer cells and MDA-MB-231 multidrug resistant breast cancer cells, giving half maximal inhibitory concentration (IC₅₀) of 0.9–1.8 μM. Confocal imaging showed its mitochondrial localization and complex 2 exhibited anti-metastasis properties. Immunostaining of β-tubulin and Annexin V-FITC/propidium iodide staining displayed complex 2 induced photo-selective microtubule rupture and cellular apoptosis, respectively.

Transmission Porosimetry Study on High‐quality Zr‐fum‐MOF Thin Films

Posted on 27 September 2023 by

Zr-fum-MOF thin films of high optical quality were synthesized using the solvothermal direct growth method. The optical properties of the thin films were investigated thoroughly in different gas atmospheres.

Abstract

Crystalline Zr-fum-MOF (MOF-801) thin films of high quality are prepared on glass and silicon substrates by direct growth under solvothermal conditions. The synthesis is described in detail and the influence of different synthesis parameters such as temperature, precursor concentration, and the substrate type on the quality of the coatings is illustrated. Zr-fum-MOF thin films are characterized in terms of crystallinity, porosity, and homogeneity. Dense films of optical quality are obtained. The sorption behavior of the thin films is studied with various adsorptives. It can be easily monitored by measuring the transmission of the films in gas flows of different compositions. This simple transmission measurement at only one wavelength allows a very fast evaluation of the adsorption properties of thin films as compared to traditional sorption methods. The sorption behavior of the thin films is compared with the sorption properties of Zr-fum-MOF powder samples.

Photophysical Properties of Boron‐Based Chromophores as Effective Moieties in TADF Devices: A Computational Study

Posted on 27 September 2023 by nPelin Ulukan, nAntonio Monari, nSaron Catakn

The relationship between molecular structure and photophysical properties of a range of boron-based TADF molecules were investigated to provide a clear approach to the structure-performance relation. Torsion angles, excited state energy alignments, singlet-triplet energy gaps, particle-hole orbital overlap extent and spin orbit coupling for reverse intersystem crossing processes were utilized.

Abstract

Thermally activated delayed fluorescence (TADF) materials have shown great potential in the design of organic metal-free optoelectronic devices and materials and, therefore, are the subject of intense investigations. This contribution presents the effects of various parameters on the photophysical properties of a series of boron-based TADF emitters. These include torsion angle, the changes in the electronic density, energy gap between the first excited singlet (S₁) and the first excited triplet states (T₁), oscillator strength (f) and spin-orbit coupling (SOC). Through a comprehensive structural analysis, we first show the most favorable conformation of the ground state of donor (D) and acceptor (A) moieties that are popular in TADF emitters. Further, the properties of the excited state manifolds are obtained with Tamm-Dancoff Approximation (TDA), thus rationalizing their optical and photophysical properties. Globally, our results settle the basis for the rationalization of the effects of different parameters on reverse intersystem crossing (RISC) probabilities, which is the rate-limiting step for TADF, thus favoring the rational design of novel highly efficient TADF materials with strong triplet exciton harvesting.

Good Practices and Practical Considerations for Research with Perfluoroalkyl Substances

Posted on 27 September 2023 by nChloe M. Taylor, nMichael C. Breadmore, nNathan L. Kilahn

Perfluoroalkyl substances (PFAS) are a class of molecules of increasing awareness and concern. Their unique properties, hazards, and complications are not always obvious, which can impede or convolute analyses, particularly at low concentrations. We have summarised “best practice” approaches for working with PFAS with the aim of enabling chemists to do so with increased confidence and safety.

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a class of hazardous pollutant that are ubiquitous in our modern world. Current research is driven by an increased awareness and concern regarding the safety of PFAS for the general population, while tightening regulations have prompted the need for detection and quantification techniques from a wide range of matrices. PFAS are a group of molecules offering unique behaviours, hazards, and complications that are not obvious or readily apparent from reading the literature. These peculiarities can impede or convolute analyses when not considered in experimental design. Drawing on the knowledge of a range of literature sources, this tutorial review looks to highlight and amalgamate the valuable suggestions and methodologies currently available to enable successful PFAS research in any laboratory.