Hydrogen Atoms Research Articles

Discrimination of Perfluorinated Arenes/Alkanes by Modulable Polyaromatic Capsules.

Efficient and selective binding of perfluorocarbons (PFCs), comprising only fluorine and carbon atoms, unlike hydrocarbons, remains quite difficult owing to the repulsive nature of fluorine. Here we describe that a cavity modulation strategy enables metal-linked polyaromatic capsules to quantitatively bind PFCs with excellent selectivity. From a mixture of perfluoroarene and the corresponding perfluoroalkane (i.e., perfluoronaphthalene and perfluorodecalin), a Pt(II)-linked capsule exclusively binds the arenes in water at room temperature, via effective D-A-A-D π-stacking interactions. The size-selective binding toward perfluoroarenes (i.e., perfluoronaphthalene and perfluorobenzene) is improved by using the analogous N-doped capsule from 85% to quantitative selectivity. Furthermore, unlike the Pt(II)-capsule, an isostructural Pd(II)-linked capsule displays the unusual length/shape-selective binding of linear/cyclic perfluoroalkanes (i.e., perfluoroheptane and perfluorodecalin) under similar conditions. Recognition of substituted hydrogen atoms on perfluorobiphenyl can also be accomplished using the Pt(II)-capsule. Various PFCs are thus clearly distinguished for the first time by the modulable polyaromatic capsules under ambient aqueous conditions.

Investigating C−D out-of-plane vibrational modes in PAHs as a tool to study interstellar deuterium-containing PAHs

Abstract Previous as well as recent observations by ISO, Spitzer, AKARI, SOFIA, JWST etc. have revealed various characteristics of mid-infrared emission bands between 3−20 $\rm \mu m$. Subsequently, several forms of organics including Polycylic Aromatic Hydrocarbons (PAHs)/PAH-like molecules are proposed as carriers for these bands. Deuterated PAH (PAD) is one such substituted PAH, which is proposed as a potential candidate carrier for weak emission bands at 4.4 and 4.65 $\mu \rm m$, detected towards few astronomical targets and are characteristics of aromatic and aliphatic C−D stretching modes in a PAD molecule, respectively. However, the 4.4 μm band is not widely detected. In order to validate PADs as carriers for mid-infrared emission bands, an additional alternative tool is crucial. If PAHs are deuterated, they should also possess an inherent signature from the C−D out-of-plane (C−D$\rm _{oop}$) vibrations, which are at the longer wavelength side. In this report, features due to C−D$\rm _{oop}$ modes in PAHs bearing a single to multiple deuterium atoms are reported by performing quantum-chemical calculations. This paper reports that some of the C−D$\rm _{oop}$ vibrations appear at the 14 − 19 μm range. Also, the strength of C−D$\rm _{oop}$ modes is not proportional to the D/H ratio in PAHs. In addition, a moderate change in the spectra of deuterated PAHs is observed from that of the undeuterated counterparts, as deuteration would alternate the adjacency class of the C-H bonds and the symmetry of the molecule. We discuss the efficiency and usefulness of these bands to constrain the form of PAHs emitting mid-infrared emission bands.

Channel-resolved photoionization time delay of hydrogen atoms in two-color ultraviolet laser fields

Channel-resolved photoionization time delay of hydrogen atoms in two-color ultraviolet laser fields

Manipulating Molecular Stacking for Semitransparent Organic Photovoltaics Achieving Light Utilization Efficiency >6.

The trade-off between average visible transmittance (AVT) and power conversion efficiency (PCE), governed by the molecular stacking of the donor and acceptor materials in semitransparent organic solar cells (ST-OSCs), significantly constrains improvements in light utilization efficiency (LUE). Here, simultaneous enhancement of AVT and PCE is achieved by meticulously designing host-guest active layers to fine-tune the molecular stacking. A systematic investigation of various host donor and guest material combinations reveals that the donor material (D18) with more electron-deficient hydrogen atoms tends to form C─H···O interactions with the guest material (BTO-BO) that features electron-rich oxygen atoms. Hydrogen bonding interactions between host donor D18 and guest BTO-BO facilitate the transition from mixed J-type and H-type molecular stacking modes of the donor to predominant J-type stacking during crystallization, significantly reducing visible absorption and enhancing hole transport. Additionally, BTO-BO can act as a nucleation agent for the host acceptor BTP-eC9 to increase the crystallinity and absorption coefficient of the active layer, thereby, enhancing near-infrared light absorption. The resultant toluene-processed ST-OSCs with optical modulation exhibit simultaneous improvement in PCE and AVT, delivering record LUEs of 6.02%. Notably, this host-guest active layer demonstrates exceptional compatibility with flexible devices and promising scalability for greenhouse photovoltaic applications.

Polymer Chain Modification via HAT Chemistry and Its Application in Graft Copolymer Synthesis.

Hydrogen atom transfer (HAT) chemistry has emerged as a powerful tool for selective molecular functionalization, with significant applications in the pharmaceutical and agricultural industries. More recently, HAT has been explored in polymer chemistry as a versatile strategy for introducing targeted functional groups onto polymer chains, enabling precise control over properties such as solubility and mechanical strength. This study investigates the use of HAT to synthesize reversible addition-fragmentation chain transfer (RAFT) agents (or chain transfer agents, CTAs) by modifying various substrates, including toluene, ethyl acetate, and dioxane, in the presence of bis(dodecylsulfanylthiocarbonyl) disulfide or bis(3,5-dimethyl-1H-pyrazol-1-ylthiocarbonyl) disulfide. The resulting CTAs were evaluated in both thermal and photoinduced electron transfer (PET)-RAFT polymerization for controlled polymerization of various monomers. This approach was then extended to functionalize polycaprolactone (PCL) and polyvinyl acetate (PVAc), enabling the synthesis of graft copolymers with various vinyl monomers. To promote HAT, a range of photocatalysts, including iron(III) chloride (FeCl3), were investigated, offering advantages over conventional thermal HAT systems. Photocatalysis enables mild and efficient radical generation under light irradiation, providing a cost-effective and environmentally friendly alternative to expensive or toxic metal catalysts.

Radical Chemistry of Tetrazenes: Access to Polymers with Pristine Tetrazenyl Chain Ends and Depolymerization Applications.

We report the first radical reaction of tetrazenes -i. e. functions with four consecutive nitrogen atoms with a linear N-N=N-N chain- that retains the characteristic 4N pattern. Selective hydrogen atom transfer (HAT) in the α-position of the 4N chain enables the free radical polymerization of various polar and non-polar monomers. The tetrazene units play a dual role. Its decomposition generates aminyl radicals that can undergo HAT and lead to initiating C-centered radicals. Contrary to what was previously thought the aminyl radicals never add to the monomers. The polymers obtained feature tetrazene chain ends, which can be harnessed as macro-initiators to further grow the polymer chains. Heating of the former above the ceiling temperature leads to cleavage of the tetrazene function, which enables depolymerization by unzipping of polymethyl methacrylate (PMMA) and polystyrene (PS).

Photoredox Site-Selective C(sp3)-H Alkylation of 1-(o-Iodoaryl)-alkan-1-ones with Activated Alkenes Enabled by Hydrogen Atom Transfer.

A visible-light-mediated photoredox catalysis for β-C(sp3)-H alkylation of 1-(o-iodoaryl)alkan-1-ones with alkenes via 1,5-hydrogen atom transfer and alkene alkylarylation to produce diverse β-alkyl arylalkanones containing a quaternary carbon center is presented. This method is applicable to a wide range of 1-(o-iodoaryl)alkan-1-ones and activated alkenes. Mechanistic studies suggest that the reaction involves a radical process.

Formation of TEMPO Adducts with Hydrogen Atom Transfer: An Alternative Pathway to Versatile Hydrofunctionalizations of Olefins.

A two-step process is developed to access a broad range of hydrofunctionalization of olefins, by combining a cobalt-catalyzed formation of TEMPO adduct from olefins and a photocatalytic nucleophilic addition to generate a new C-C, C-N, C-O, C-F, and C-Cl bond. Nucleophilic fluorination can be achieved with a short reaction time, showing its potential in PET applications. Combining the two steps, net hydrofunctionalization of olefins with a broad range has been achieved.

Upper bounds on the highest phonon frequency and superconducting temperature from fundamental physical constants

Fundamental physical constants govern key effects in high-energy particle physics and astrophysics, including the stability of particles, nuclear reactions, formation and evolution of stars, synthesis of heavy nuclei and emergence of stable molecular structures. Here, we show that fundamental constants also set an upper bound for the frequency of phonons in condensed matter phases, or how rapidly an atom can vibrate in these phases. This bound is in agreement withab initiosimulations of atomic hydrogen and high-temperature hydride superconductors, and implies an upper limit to the superconducting transition temperatureTcin condensed matter. Fundamental constants set this limit to the order of 102-103K. This range is consistent with our calculations ofTcfrom optimal Eliashberg functions. As a corollary, we observe that the very existence of the current research of findingTcat and above 300 K is due to the observed values of fundamental constants. We finally discuss how fundamental constants affect the observability and operation of other effects and phenomena including phase transitions.

Cadmium passivation induced negative differential resistance in cove edge graphene nanoribbon device

Graphene nanoribbons (GNRs) have emerged as promising candidates for nanoelectronic devices due to their unique electronic and transport properties. In this study, we investigate the impact of passivation on cove-edge graphene nanoribbon (CGNR) using both cadmium (Cd) and hydrogen (H) atoms. Through a comprehensive density functional theory (DFT) analysis coupled with non-equilibrium Green’s function (NEGF) simulations, we explore the electronic transport properties and device behavior of these passivated CGNRs. Our results reveal a distinctive semiconductor-to-metal transition in the electronic properties of the Cd-passivated CGNRs. This transition, induced by the interaction between Cd atoms and the GNR edges, leads to a modulation of the bandstructure and a pronounced shift in the conductance characteristics. Interestingly, the Cd-passivated CGNR devices exhibit negative differential resistance (NDR) with remarkably high peak-to-valley current ratios (PVCRs). NDR is a phenomenon critical for high-speed switching, enables efficient signal modulation, making it valuable for nanoscale transistors, memory elements, and oscillators. The highest PVCR is measured to be 53.7 for Cd-CGNR-H which is x10 and x17 times higher than strained graphene nanoribbon and silicene nanoribbon respectively. These findings suggest the promising potential of passivated CGNRs as novel components for high-performance nanoelectronic devices.

Impact of Lewis Acids on the Reactivity of a High-Valent Cu(III) Complex.

Redox-inactive metal ions functioning as Lewis acids (LA) play a significant role in modulating the redox reactivity of metal-oxygen intermediates such as metal-oxo, metal-superoxo, and metal-peroxo species. In photosystem II (PS-II), the redox-inactive metal ion CaII is critical for O2 activation, although its precise function remains unclear. Inspired by nature's use of redox-inactive metal ions, this study aims to characterize complexes of high-valent Cu(III) bound Lewis acids, 2-M (where M = ZnII, EuIII, YbIII, and ScIII), through various spectroscopic techniques, including UV-vis and resonance Raman spectroscopic analyses. These experimental findings are further supported by computational studies. Furthermore, the binding of a redox-active Lewis acid like CeIII was also investigated, where inner-sphere electron transfer between 2 and CeIII is witnessed. Notably, the electron transfer rate between CeIII and 2 is greatly influenced by the binding of other Lewis acids. Additionally, we demonstrated the impact of LA on electron transfer (ET) and hydrogen atom transfer (HAT) reactivity. Our findings show that while the introduction of LA decreases the HAT reaction rate, it conversely leads to enhanced electron transfer reactivity.

The effect of Coulomb potential on phase-of-phase attoclock spectroscopy: hydrogen atom as an example

The effect of Coulomb potential on phase-of-phase attoclock spectroscopy: hydrogen atom as an example

Synthesis of Unnatural Amino Acids via β‐Aminoaldehyde C–H Arylation using HAT‐Metallaphotoredox Catalysis

Unnatural amino acids play a crucial role in advancing protein engineering and drug development. In this study, we present the synthesis of a series of γ aryl‐keto‐α‐amino acids through the direct C–H arylation of readily accessible β‐aminoaldehydes and aryl bromides, promoted by hydrogen atom transfer combined with metallaphotoredox catalysis. This direct and mild methodology provides access to enantiopure L‐ and D‐ amino acids, either N‐protected or unprotected, with broad functional group compatibility, including pyridine heterocycles. These features highlight the potential relevance of this strategy for pharmaceutical synthesis and biotechnological research.

Metal-Free Photoinduced Cascade Cyclization of Alkyne-Tethered N-Alkoxybenzamides

AbstractIn this work, a photoinduced synthesis of isoxazolidine-fused isoquinolin-1-ones and 3,4-dihydro[1,2]oxazino[2,3-b]isoquinolin-10(2H)-one from alkyne-tethered N-alkoxybenzamides is reported. The gram-scaled synthesis and structural elaboration of isoxazolidine-fused isoquinolin-1-ones are also realized. The reaction is promoted by an equimolar amount of tetrabutylammonium chloride, under metal- and catalyst-free conditions. In the reaction, it is believed that the alkyne-tethered N-alkoxybenzamide starting materials serve as photosensitizers, and the photoexcited substrate induces the formation of a chloro radical. The N-radical results from hydrogen atom abstraction by the chloro radical at the N–H bond of the substrates.

A Review of Decontamination of Aspergillus spp. and Aflatoxin Control for Grains and Nuts with Atmospheric Cold Plasma

Aspergillus spp. and their produced aflatoxins are responsible for contaminating 25–30% of the global food supply, including many grains, and nuts which when consumed are detrimental to human and animal health. Despite regulatory frameworks, Aspergillus spp. and aflatoxin contamination is still a global challenge, especially in cereal-based matrices and their derived by-products. The methods for reducing Aspergillus spp. and aflatoxin contamination involve various approaches, including physical, chemical, and biological control strategies. Recently, a novel technology, atmospheric cold plasma (ACP), has emerged which can reduce mold populations and also degrade these toxins. ACP is a non-thermal technology that operates at room temperature and atmospheric pressure. It can reduce mold and toxins from grains and seeds without affecting food quality or leaving any chemical residue. ACP is the conversion of a gas, such as air, into a reactive gas. Specifically, an electrical charge is applied to the “working” gas (air) leading to the breakdown of diatomic oxygen, diatomic nitrogen, and water vapor into a mixture of radicals (e.g., atomic oxygen, atomic nitrogen, atomic hydrogen, hydroxyls), metastable species, and ions (e.g., nitrate, nitrite, peroxynitrate). In a cold plasma process, approximately 5% or less of the working gas is ionized. However, cold plasma treatment can generate over 1000 ppm of reactive gas species (RGS). The final result is a range of bactericidal and fungicidal molecules such as ozone, peroxides, nitrates, and many others. This review provides an overview of the mechanisms and chemistry of ACP and its application in inactivating Aspergillus spp. and degrading aflatoxins, serving as a novel treatment to enhance the safety and quality of grains and nuts. The final section of the review discusses the commercialization status of ACP treatment.

Mannich Bases: Promising Scaffolds for the Treatment of Infectious Diseases.

Mannich bases, synthesized through the reaction of an aldehyde, a primary or secondary amine, and a compound bearing an acidic hydrogen atom, represent a versatile class of scaffolds in medicinal chemistry. This review explores their broad spectrum of biological activities, emphasizing their potential in combating infectious diseases. With demonstrated efficacy against bacteria, fungi, and parasites, Mannich bases stand out as promising candidates for the development of novel therapeutic agents. Their versatility arises from the ability of their electronic, steric, and conformational parameters to modulate receptor interactions, significantly expanding their applicability in drug design. The review provides an in-depth analysis of the structure-activity relationship (SAR) of Mannich bases, highlighting how specific structural modifications enhance their biological activity. Additionally, it examines the lipophilic properties of these compounds, offering key insights into their influence on pharmacokinetics and pharmacodynamics. This understanding is essential for optimizing the development of novel therapeutics, particularly for addressing challenging infectious diseases. By integrating these aspects, this review underscores the pivotal role of Mannich bases in overcoming current challenges in drug resistance and shaping the future of drug discovery and development.

Gauge-invariant description of a Dirac electron moving in a noncommutative gauge-field background

Abstract We provide a gauge invariant description of the quantum dynamics of an electron in a constant noncommutative (NC) gauge field background using the Dirac equation in an NC plane. We show that the physical force imparted on the electron is the standard Lorentz force but with modified NC magnetic fields that pick up two different first order corrections in the relativistic and non-relativistic (NR) domains. Taking NR limit of our Dira equation we show that noncommutativity affects the cyclotron frequency but leaves the Hall conductivity and cyclotron motion trajectory unaffected to first order in the NC parameter. The hyperfine splitting of Hydrogen atom (H-atom) spectrum also shows a first order correction.

Looking at the Distant Universe with the MeerKAT Array: The H i Mass Function in the Local Universe

Abstract We present measurements of the neutral atomic hydrogen (H i) mass function (HiMF) and cosmic H i density (ΩH I) at 0 ≤ z ≤ 0.088 from the Looking at the Distant Universe with MeerKAT Array (LADUMA) survey. Using LADUMA Data Release 1 (DR1), we analyze the HiMF via a new “recovery matrix” method that we benchmark against a more traditional modified maximum likelihood (MML) method. Our analysis, which implements a forward modeling approach, corrects for survey incompleteness and uses extensive synthetic source injections to ensure robust estimates of the HiMF parameters and their associated uncertainties. This new method tracks the recovery of sources in mass bins different from those in which they were injected and incorporates a Poisson likelihood in the forward modeling process, allowing it to correctly handle uncertainties in bins with few or no detections. The application of our analysis to a high-purity subsample of the LADUMA DR1 spectral line catalog in turn mitigates any possible biases that could result from the inconsistent treatment of synthetic and real sources. For the surveyed redshift range, the recovered Schechter function normalization, low-mass slope, and “knee” mass are ϕ * = 3.5 6 − 1.92 + 0.97 × 1 0 − 3 Mpc−3 dex−1, α = − 1.1 8 − 0.19 + 0.08 , and log ( M * / M ⊙ ) = 10.0 1 − 0.12 + 0.31 , respectively, which together imply a comoving cosmic H i density of Ω H I = 3.0 9 − 0.47 + 0.65 × 1 0 − 4 . Our results show consistency between recovery matrix and MML methods and with previous low-redshift studies, giving confidence that the cosmic volume probed by LADUMA, even at low redshifts, is not an outlier in terms of its H i content.

In situ Doping Coupling With Vacancy Regulation Induced Strong Metal‐Support Interaction in Ni/CaTiO3 to Boost Supercharged Photothermal CO2 Methanation

AbstractThe “Solar Sabatier” reaction has emerged as a promising sustainable method for the CO2 hydrogenation. The development of advanced metal‐support catalysts based on Strong Metal‐Support Interaction (SMSI) offers significant advantages in the activation of CO2 and the regulation of selectivity. Herein, a novel composite Ni/CaTiO3 catalyst consisting of Ni and Ni‐doped CaTiO3 is synthesized and utilized in the CO2 methanation. A noteworthy finding is that the incorporation of Ni into the CaTiO3 matrix is instrumental in the formation of oxygen vacancies and the establishment of SMSI between Ni and CaTiO3. The enhanced SMSI resulting from the surface‐doped Ni atoms not only facilitated effective interface contact between metallic Ni and the CaTiO3 surface but also significantly improved the migration efficiency of hydrogen atoms reduced the reaction barrier for CO2 methanation and optimized the rate‐limiting step, all of which are advantageous for the CO2 methanation. Consequently, the optimized catalysts exhibited extraordinary performance, achieving a CO2 conversion rate of 87.77%, CH4 generation rate of 3.12 mol gNi−1 h−1, and ≈100% CH4 selectivity under ambient pressure conditions. This investigation lays the groundwork for the design of highly active “Solar Sabatier” catalysts and offers a novel understanding of the mechanisms underlying effective SMSI.

Ion-Pair Hydrogen Atom Transfer Catalysis Enables Cr-Catalyzed Allylation of Ketones Using Hydrocarbon Alkenes.

We report a catalytic allylation of ketones using simple hydrocarbon alkenes, enabled by a synergistic system comprising chromocene and photo-activatable ion-pair hydrogen atom transfer (IP-HAT) catalysts derived from a thiophosphoryl imide and N-heteroaromatics. This catalyst system generates highly nucleophilic, electron-rich allylchromium(III) species directly from unactivated alkenes, demonstrating broad applicability to various ketones, including aromatic, aliphatic, and multifunctional ketones. The reaction proceeds under mild conditions with high functional group tolerance. The modular design of the IP-HAT catalysts allows precise tuning of redox potential and HAT activity, with the enhanced reduction potential of the reduced N-heteroaromatics catalyst playing a pivotal role in efficiently regenerating the electron-rich chromocene(II) catalyst.