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On-Demand Nitric Oxide Generation via Thermal Decomposition of N-Trityl Dihydro-1,2-Oxazines
No full textInhaled nitric oxide (iNO) is a promising therapy for a wide variety of pulmonary conditions but is limited by the cost, portability, and safety limitations of the compressed gas cylinders used in conventional iNO delivery systems. On-demand generation of iNO via thermally controlled decomposition of an NO-genic precursor is an attractive alternative to systems based on compressed gas cylinders. However, most NO-releasing materials, which would form the basis of such a system, are designed for in-vivo applications, not gas flow release at elevated temperatures. Novel NO donors with tunable kinetics suited for simple thermal generation are needed to realize such iNO delivery systems. Here we report the development of a patently new class of NO donors based on N-trityl 3,6-dihydro-1,2-oxazines. We show that these molecules release nitric oxide when heated above 90 °C and that their release kinetics can be modified through variation of the substitution pattern on the oxazine ring. Amorphous solid dispersions of these molecules in porous polymers exhibit consistent, thermoresponsive gas flow nitric oxide release. Collectively, this work adds a new class of NO donor to the basis set of known NO-genic molecules and establishes a potential technological basis for a low-power, small-footprint iNO delivery system
Highly Rigid, yet Conformationally Adaptable, Bisporphyrin sp2-Cage Receptors Afford Outstanding Binding Affinities, Chelate Cooperativities, and Substrate Selectivities
No full textIf we aim to develop efficient synthetic models of protein receptors and enzymes, we must understand the relationships of intra- and intermolecular interactions between hosts and guests and how they mutually influence their conformational ener-gy landscape, so as to adapt to each other to maximize binding energies and enhance substrate selectivities. Here, we intro-duce a novel design of cofacial (ZnII)bisporphyrin cages based on dynamic imine bonding, which is synthetically simple, but at the same time highly robust and versatile, affording receptors composed of only sp2-hybridized C and N atoms. The high structural rigidity of these cages renders them ideal hosts for ditopic molecules that can fit into the cavity and bind to both metal centers, leading to association constants as high as 109 M-1 in chloroform. These strong binding affinities are a consequence of the remarkable chelate cooperativities attained, with effective molarity (EM) values reaching record values of up to 103 M. However, we discovered that the cages can still adapt their structure to a more compact version, able to host slightly smaller guests. Such conformational transition has an energy cost, which can be very different depending on the direction of the imine linkages in the cage skeleton, and which results in EM values 2 to 4 orders of magnitude lower. This interplay between cooperativity and conformational adaptability leads to strong and unusual selectivities. Not only these metalloporphyrin receptors can choose to bind preferably a particular guest, as a function of its size, but also the guest can select which host to bind, as a function now of the host conformational rigidity. Such highly cooperative and selective asso-ciations are lost, however, in related flexible receptors where the imine bonds are reduced
Bayesian Illumination: Inference and Quality-Diversity Accelerate Generative Molecular Models
No full textIn recent years, there have been considerable academic and industrial research efforts to develop novel generative models for high-performing, small molecules. Traditional, rules-based algorithms such as genetic algorithms [Jensen, Chem. Sci., 2019, 12, 3567-3572] have, however, been shown to rival deep learning approaches in terms of both efficiency and potency. In previous work, we showed that the addition of a quality-diversity archive to a genetic algorithm resolves stagnation issues and substantially increases search efficiency [Verhellen, Chem. Sci., 2020, 42, 11485-11491]. In this work, we expand on these insights and leverage the availability of bespoke kernels for small molecules [Griffiths, Adv. Neural. Inf. Process. Syst., 2024, 36] to integrate Bayesian optimisation into the quality-diversity process. This novel generative model, which we call Bayesian Illumination, produces a larger diversity of high-performing molecules than standard quality-diversity optimisation methods. In addition, we show that Bayesian Illumination further improves search efficiency com- pared to previous generative models for small molecules, including deep learning approaches, genetic algorithms, and standard quality-diversity methods
Transparent conductive PEDOT–graphene films from large- flake graphite
No full textThe demand for affordable, flexible, transparent, and robust thin film electrodes in organic electronics has highlighted the limitations of indium tin oxide (ITO), which suffers from fragility and high costs. Poly(3,4- ethylenedioxythiophene) (PEDOT), particularly when doped with poly(styrene sulfonate) (PSS), has emerged as a promising alternative due to its mechanical flexibility, electrical conductivity, and environmental stability. However, PSS\u27s insulating nature, hygroscopicity, and acidity present significant drawbacks. This study explores an alternative approach using large-flake graphene, exfoliated through a solvent interface trapping method (SITM), as a dopant for PEDOT. The resulting PEDOT-graphene films exhibit conductivities reaching 1070 S/cm, surpassing those of previously reported PEDOT-based films. The graphene sheets, acting as templates during vapor-phase polymerization (VPP) of PEDOT, enhance the film\u27s conductivity by increasing electron pathways and crystalline regions within PEDOT. Characterization through SEM, TEM, XRD, Raman spectroscopy, XPS, and UV-Vis spectroscopy confirms the structural and electrical integrity of the films. Additionally, these films demonstrate potential applications in sensing technologies, particularly responsive to volatile organic compounds such as triethylamine. This work presents a scalable method for producing high-conductivity, transparent PEDOT- graphene films, offering a viable alternative to ITO in organic electronic applications
A Balance of Unimolecular and Bimolecular Pathways Control the Temperature-Dependent Kinetics of Ozonolysis in Aerosols
No full textTo better understand the key kinetic mechanisms controlling heterogeneous oxidation in organic aerosols, submicron particles composed of an alkene and a saturated carboxylic acid are exposed to ozone in a variable-temperature flow tube reactor. Effective uptake coefficients (γ_eff) are obtained from the multiphase reaction kinetics, which are quantified by Vacuum Ultraviolet Photoionization Aerosol Mass Spectrometry. For aerosols composed of only of alkenes, γ_eff doubles (from 6x10-4 to 1.2x10-3) when the temperature is decreased from 293 to 263 K. Alternatively, for an alkene particle doped with a carboxylic acid, an efficient scavenger of stabilized Criegee Intermediates (sCI), γ_eff is observed to be weakly temperature dependent. A kinetic model, benchmarked to literature data, explains these results as arising from the temperature dependent competition between unimolecular pathways of sCI that promote radical chain cycling and those bimolecular pathways that form stable chain termination products (i.e., ɑ-acyloxyalkyl hydroperoxides). The implication of these results for the kinetics of aerosol aging at low temperatures is discussed
Entropy-driven supramolecular glass processed under ambient heating
No full textGlass is an indispensable material in both industrial manufacturing and everyday life. Its development has spanned from traditional silicate glasses to advanced forms such as polymers, amorphous metals, and organic or hybrid glasses. Herein, a novel benzoguanamine-derived supramolecular glass (BGG) is synthesized through a straightforward process: a commercially available molecule is heated in an ambient environment, which condenses into a series of oligomers and forms a melted and homogenous matter. The high-entropy nature of the liquid intermediate is highly unfavorable to crystallization, as a result, natural cooling allows for curing and leads to the formation of rigid supramolecular glass, which is reminiscent of the traditional procedures of inorganic glass production. The prepared BGG features remarkable optical properties and ease of manipulation and scalability, which renders it an excellent candidate for applications in films and fibers for photovoltaics and photonic waveguides. Furthermore, various energy-transfer hybrids are developed based on the BGG framework, including solid solutions with fluorescent molecules and core-shell nanocomposites integrated with perovskite particles, which showcases its versatility as a platform for creating advanced materials with tailored properties
Transparent, ferroelectric Ca:HfO2 and Sr:HfO2 films grown from chemical solution on ITO-coated glass
No full textThe discovery of ferroelectricity in HfO2 thin films has revived the interest on ferroelectric-based memories. Yet, other applications like transparent micro sensors and actuators are also potentially possible. By using a simple chemical solution method, we achieved the growth of transparent Ca:HfO2 and Sr:HfO2 films on ITO coated glass and reached polarization values of 12 and 6 µC/cm2, respectively, after deposition of top Pt electrodes. The selection of Ca or Sr as doping element brought about large variations in thermal conditions at which ferroelectricity in doped-HfO2 films was achieved. Sr:HfO2 required significantly shorter annealing times than Ca:HfO2 and caused deformation of the glass substrate despite otherwise equal processing conditions. Moreover, although, both Ca and Sr induced the crystallization of hafnia into high symmetry phases, the latter also enhanced the appearance of the monoclinic structure. Interestingly, high resolution transmission microscopy revealed a semi-epitaxial “cube on cube” growth of doped-HfO2 on individual ITO crystals. This predicts that accomplishing fully epitaxial HfO2 films by a chemical solution method should be possible. Technological innovation might come from achieving fully transparent ferroelectric/piezoelectric HfO2-based devices
Easily Accessible and Solution-Stable Ni(0) Precatalysts for High-Throughput Experimentation
No full textWe report the synthesis, characterization, and catalytic applications of N,N’-diaryl diazabutadiene (DAB) Ni(0) complexes stabilized by alkene ligands. These complexes are soluble and stable in several organic solvents, making them ideal candidates for in situ catalyst formation during high-throughput experimentation (HTE). We used HTE to evaluate these Ni(0) precatalysts in a variety of Suzuki and C–N coupling reactions, and they were found to have equal or better performance than the still ‘industry-standard’ Ni(0) source, Ni(COD)2
First Principles Assessment of ZnTe and CdSe as Prospective Tunnel Barriers at the InAs/Al Interface
No full textMajorana zero modes are predicted to emerge in superconductor/semiconductor interfaces, such as Al/InAs. Majorana modes could be utilized for fault tolerant topological qubits. However, their realization is hindered by materials challenges. The coupling between the superconductor and the semiconductor may be too strong for Majorana modes to emerge, due to effective doping of the semiconductor by the metallic contact. This could be mediated by adding a tunnel barrier of controlled thickness. We use density functional theory (DFT) with Hubbard U corrections, whose values are machine-learned via Bayesian optimization (BO) to assess ZnTe and CdSe as prospective tunnel barriers for the InAs/Al interface. The results of DFT+U(BO) for ZnTe are validated by comparison to angle resolved photoemission spectroscopy (ARPES). We then study bilayer interfaces of the three semiconductors with each other and with Al, as well as tri-layer interfaces with a varying number of ZnTe or CdSe layers inserted between InAs and Al. We find that 16 atomic layers of either material completely insulate the InAs from metal induced gap states (MIGS). However, ZnTe and CdSe differ significantly in their band alignment, such that ZnTe forms an effective barrier for electrons, whereas CdSe forms a barrier for holes. Because of Fermi level pinning in the conduction band at the surface, only electron transport is possible in InAs-based devices. Therefore, ZnTe is the better choice. Based on the results of our simulations, we suggest conducting experiments with ZnTe barriers in the thickness range of 6-18 atomic layers
C(sp3)–H Carboxylation via Carbene/Photoredox Cooperative Catalysis
No full textC(sp3)–H bond functionalization is a powerful strategy for the synthesis of organic compounds due their abundance in simple starting materials. Photoredox catalysis has led to a diverse array of enabling C(sp3)–H activation strategies; however, the direct functionalization of C(sp3)–H to carboxylic acid derivatives remains underexplored. Disclosed herein is the development of a cooperative NHC/photoredox-catalyzed C(sp3)–H esterification transformation. This method enables access to benzylic, –heteroatom, and formal β-esterification products in good to excellent yields under mild reaction conditions