Triplet Reaction Research Articles

Quantitative measurements of reactive oxygen species partitioning in electron transfer flavoenzyme magnetic field sensing.

Biological magnetic field sensing that gives rise to physiological responses is of considerable importance in quantum biology. The radical pair mechanism (RPM) is a fundamental quantum process that can explain some of the observed biological magnetic effects. In magnetically sensitive radical pair (RP) reactions, coherent spin dynamics between singlet and triplet pairs are modulated by weak magnetic fields. The resulting singlet and triplet reaction products lead to distinct biological signaling channels and cellular outcomes. A prevalent RP in biology is between flavin semiquinone and superoxide (O2 •-) in the biological activation of molecular oxygen. This RP can result in a partitioning of reactive oxygen species (ROS) products to form either O2 •- or hydrogen peroxide (H2O2). Here, we examine magnetic sensing of recombinant human electron transfer flavoenzyme (ETF) reoxidation by selectively measuring O2 •- and H2O2 product distributions. ROS partitioning was observed between two static magnetic fields at 20nT and 50μT, with a 13% decrease in H2O2 singlet products and a 10% increase in O2 •- triplet products relative to 50µT. RPM product yields were calculated for a realistic flavin/superoxide RP across the range of static magnetic fields, in agreement with experimental results. For a triplet born RP, the RPM also predicts about three times more O2 •- than H2O2, with experimental results exhibiting about four time more O2 •- produced by ETF. The method presented here illustrates the potential of a novel magnetic flavoprotein biological sensor that is directly linked to mitochondria bioenergetics and can be used as a target to study cell physiology.

Photochemistry of Riboflavin: The Primary Transients

Abstract: Primary photoreactions of riboflavin (Rf) are considered. The goal was to present data on the transients formed under photoexcitation of Rf: excited singlet and triplet states, triplet reactions with the formation of Rf neutral free radicals, and a radical anion. The absorption spectra of transients are presented, as are the rate constants of their decay. Special attention is devoted to Rf in water (aerobic and anaerobic reactions).

Substituent influence of heteroatom on the novel remote N-heterocyclic silylenes (RNHSis) using density functional theory

In this work, we have compared and contrasted the stability, polarity, polarizability, frequency, band gap, charge distribution, and global reactivity of singlet (s) and triplet (t) states of the fused benzo-4-sila-1,4-dihydropyridine-4,4-diyl as the reference structure (1-s and 1-t) as well as the fused pyrrole congeners (2x-s, and 2x-t, x = NH, PH, AsH, O, S, and Se), using density-functional theory (DFT). According to frequency data, all singlet and triplet remote N-heterocyclic silylene (RNHSi) structures appear as minimum displaying a positive force constant. Every singlet silylene as ground state exhibits more stability than its corresponding triplet congener. Consistent with Hoffmannʼs findings, the fusion of one pyrrole ring with different heteroatoms stabilizes the corresponding RNHSi more than the fusion of one benzene ring. In going from 1-s to 2x-s species and substituting of NH, PH, AsH, O, S, and Se groups, higher singlet–triplet energy difference (ΔE s-t = E t – E s) and the higher band gap is found for 2NH-s and 2 O-s structures. Interestingly, the higher thermodynamic and kinetic stability of the optimized RNHSis than the synthesized Kiraʼs silylene makes them worthy of synthetic exploration. According to the distributed charge and FMO (the frontier molecular orbital) shapes, the more negative region is localized on pyridineʼs nitrogen and the less negative region is confined over pyrroleʼs nitrogen, while the positive charge is distributed on silylenic center. This phenomenon is inconsistent with the expected canonical forms for RNHSis.

Excited-State Intramolecular Proton Transfer in Salicylidene-α-Hydroxy Carboxylate Derivatives: Direct Detection of the Triplet Excited State of the cis-Keto Tautomer.

Excited-state intramolecular hydrogen transfer on the triplet surface of salicylideneaniline derivatives has received much less attention than the corresponding ultrafast process on the singlet surface. To enhance the understanding of this triplet reactivity, the photochemical properties of a series of salicylidene-α-hydroxy acid salts with different substituents on the phenol moiety (1-3) were characterized. UV/vis absorption and phosphorescence measurements in ethanol revealed that 1-3 exist as both enol and keto tautomers, with the enol form being predominant. Irradiation of 1 at 310 nm in ethanol glass (77 K) yielded an absorption band with a λmax at ∼405 nm, which was assigned to the trans-keto tautomer (trans-1K). In contrast, laser flash photolysis of 1-3 in methanol or acetonitrile resulted in a transient absorption with λmax at 440-460 nm. This transient, which decayed on the microsecond timescale and was significantly shorter lived in methanol than in acetonitrile, was assigned to the triplet excited state (T1) of the cis-keto tautomer (cis-1K-3K) and residual absorption of trans-1K-3K by comparison with TD-DFT calculations. The assignment of the T1 of cis-1K was further supported by quenching studies with anthracene and 2,5-dimethyl-2,4-hexadiene. Laser flash photolysis of 1 in the temperature range of 173-293 K gave an activation barrier of 6.7 kcal/mol for the decay of the T1 of cis-1K. In contrast, the calculated activation barrier for cis-1K to undergo a 1,5-H atom shift to reform 1 was smaller, indicating that intersystem crossing of the T1 of cis-1K is the rate-determining step in the regeneration of 1.

A theoretical evaluation for new fused remote N‐heterocyclic silylenes (RNHSis) using density functional theory

AbstractIn this research, we compare and contrast the stability, polarity, polarizability, band gap, and global reactivity of singlet (s) and triplet (t) fused benzene N‐heterocyclic silylene (1‐s and 1‐t) along with five numbered congeners (2x‐s, and 2x‐t, x = CH2, SiH2, GeH2, NH, PH, AsH, O, S, and Se) at DFT (density functional theory). All singlet and triplet remote N‐heterocyclic silylenes (RNHSis) appear as minima showing positive force constant. Every singlet RNHSi emerges as ground state and exhibits more stability than its corresponding triplet RNHSi. In going from 1‐s to 2x‐s species, the thermodynamic and kinetic stability is increased, so that higher ΔEs‐t (= Et − Es) and higher band gap or ΔEHOMO–LUMO (=ELUMO − EHOMO) is considered for 2CH2‐s, 2NH‐s, and 2O‐s structures. In going from second row to forth row of every group in the periodic table, electronegativity of heteroatoms have pronounced effect on the stability, polarity, polarizability, and band gap of 2x‐s species. These silylenes show more stability than the synthesized silylene by Kira. Every 2x‐t silylene shows higher nucleophilicity (about 1.6 times) than its corresponding 2x‐s analogous. Every singlet RNHSi reveals lower nucleophilicity (N), higher electrophilicity (ω), chemical potential (μ), and global hardness (η) than its triplet congener. Furthermore, 2x‐s silylenes benefit from stabilization effect of two heteroatoms synchronously in the fused five‐membered ring via mesomeric effect and π donation from the lone pairs of heteroatom to the formally vacant 3p orbital of the silylenic center. Hence, we predict higher stability as well as lower global reactivity of RNHSis than Kira's silylene will make them creditable for the synthetic research.

Arsenate Removal from the Groundwater Employing Maghemite Nanoparticles

An investigation of the potential of γ-Fe2O3 (maghemite) nanoparticles (MNPs) to remove AsV from groundwater is reported. The MNPs were synthesized using a modified co-precipitation method via refluxing. The morphological and surface characteristics of MNPs were analyzed using XRD, FTIR, SEM, TEM, and Zetasizer techniques. Their AsV removal potential was explored in synthetic water representing the elemental composition equivalent to arsenic-contaminated groundwater of the Ballia district, Uttar Pradesh, India. The arsenic concentration in the samples collected from the study area was observed to be much more than the provisional WHO guideline value for drinking water (10 µg L−1). An orthogonal array L27 (313) of the Taguchi design of experimental methodology was employed to design the experiments and optimization of AsV removal. The ANN tool was trained to evaluate Taguchi’s outcomes using MATLAB. The percentage of ionic species distribution and surface complexation modeling was performed using Visual MINTEQ. The study explored the effects of pH, temperature, contact time, adsorbent dose, total dissolved solids, and shaking speed on the removal process. The adsorption was found to occur through electrostatic interactions. The inter-parametric analysis demonstrated the involvement of secondary sites affecting the adsorption. The charge distribution multi-sites complexation (CD-MUSIC) model and 2pk-Three-Plane-Model (TPM) indicated the involvement of the reactivity of singlet (FeOH−0.5) and triplet (Fe3O−0.5) species in the examined pH range. The developed nanoparticles are observed to be efficient in AsV removal. This information could benefit field-scale arsenic removal units.

Theoretical Exploration of Energy Transfer and Single Electron Transfer Mechanisms to Understand the Generation of Triplet Nitrene and the C(sp3)-H Amidation with Photocatalysts.

Mechanistic explorations and kinetic evaluations were performed based on electronic structure calculations at the CASPT2//CASSCF level of theory, the Fermi's golden rule combined with the Dexter model, and the Marcus theory to unveil the key factors regulating the processes of photocatalytic C(sp3)-H amidation starting from the newly emerged nitrene precursor of hydroxamates. The highly reactive nitrene was found to be generated efficiently via a triplet-triplet energy transfer process and to be benefited from the advantages of hydroxamates with long-range charge-transfer (CT) excitation from the N-centered lone pair to the 3,5-bis(trifluoromethyl)benzoyl group. The properties of the metal-to-ligand charge-transfer (MLCT) state of photocatalysts, the functionalization of chemical moieties for substrates involved in the charge-transfer (CT) excitation, such as the electron-withdrawing trifluoromethyl group, and the energetic levels of singlet and triplet reaction pathways may regulate the reaction yield of C(sp3)-H amidation. Kinetic evaluations show that the triplet-triplet energy transfer is the main driving force of the reaction rather than the single electron transfer process. The effects of electronic coupling, molecular rigidity, and excitation energies on the energy transfer efficiency were further discussed. Finally, we investigated the inverted behavior of single-electron transfer, which is correlated unfavorably to the catalytic efficiency and amidation reaction. All theoretical explorations allow us to better understand the generation of nitrene with visible-light photocatalysts, to expand highly efficient substrate sources, and to broaden our scope of available photosensitizers for various cross-coupling reactions and the construction of N-heterocycles.

Enhancive and inhibitory effects of copper complexation on triplet dissolved black carbon-sensitized photodegradation of organic micropollutants

Excited-triplet dissolved black carbon (DBC) was deemed as a significant reactive intermediate in the phototransformation of environmental micropollutants, but the impacts of concomitant metal ions on photochemical behavior of excited-triplet DBC (3DBC*) are poorly understood. Here, the photolytic kinetics of sulfadiazine and carbamazepine induced by 3DBC* involving Cu2+ was explored. The presence of Cu2+ reduced the 3DBC*-induced photodegradation rate of sulfadiazine; whereas for carbamazepine, Cu2+ enhanced 3DBC*-induced photodegradation. Cu(II)-DBC complex was formed due to the decreasing fluorescence intensities of DBC in the presence of Cu2+. Cu2+ complexation caused the decrease of 3DBC* steady-state concentrations, which markedly reduced 3DBC*-induced photodegradation rate of sulfadiazine due to its high triplet reactivity. Kinetic model showed that 3DBC* quenching rate by Cu2+ was 7.98 × 109 M−1 s−1. Cu2+ complexation can also enhance the electron transfer ability, thereby producing more ∙OH in Cu(II)-DBC complex, which explains the promoting effect of Cu2+ complexation on carbamazepine photodegradation in view of its low triplet reaction rate. These indicate that 3DBC* reactivity differences of organic micropollutants may explain their photodegradation kinetics differences in DBC system with/without Cu2+, which was supported by the linearized relationship between the photodegradation rate ratios of ten micropollutants with/without Cu2+ and their triplet reaction activity.

Estimating structure, stability, and electronic properties on halogenated derivatives of 2-germabicyclo[1.1.1.]pentane-2-ylidenes at density functional theory.

In this computational survey, substituent effects of group 17 on the stability (singlet-triplet energy gaps, ΔEs-t) and reactivity of singlet (s) and triplet (t) forms of 2-germabicyclo[1.1.1.]pentane-2-ylidenes are considered by using B3LYP/6-311 + + G**, B3LYP/aug-cc-pvtz, and B3LYP/def2-TZVP level of theories. In all germylene structures, singlets appear more stable than their corresponding triplet congeners, revealing a singlet ground state and the order of stability appears to be 1,3,4,4,5,5-hexachloro-2-germabicyclo[1.1.1.]pentane-2-ylidenes (3) > 1,3,4,4,5,5-hexabromo-2-germabicyclo[1.1.1.]pentane-2-ylidenes (4) > 1,3,4,4,5,5-hexafluoro-2-germabicyclo[1.1.1.]pentane-2-ylidenes (2) > 1,3,4,4,5,5-hexaiodo-2-germabicyclo[1.1.1.]pentane-2-ylidenes (5) > 2-germabicyclo[1.1.1.]pentane-2-ylidenes (1), at the three levels of theory. The positive and negative effects on germylene stability are LP(F, Cl, Br, and I) → LP*G̈e and σ(C-Ge) → σ*(C-F, Cl, Br, and I) interactions, respectively. The results of our calculations show that every singlet germylene with high LP(F, Cl, Br, and I) → LP*G̈e interactions has higher electrophilicity. Also, in going from the most electronegative F to the least electronegative I, the nucleophilicity index (N) for germylene increases. Finally, this survey introduces that germylene 4s with rather high band gap (ΔEHOMO-LUMO = 97.19kcal/mol), nucleophilicity (2.20eV), and stability (ΔEs-t = 76.95kcal/mol) has high proton affinity (171.55kcal/mol) that can be applied as multidentate ligands and it is hoped that this will prompt experimental attention toward its.

The noncovalent interaction between water and the 3P ground state of the oxygen atom*

ABSTRACT The reaction between two OH radicals has been studied in the context of combustion chemistry, atmospheric chemistry, and astrochemistry. The global minimum on the triplet reaction surface is the van der Waals complex between water and O( 3 P) atom. We optimised the geometry of the system using ab initio methods up to CCSDT/aug-cc-pVQZ. We use the focal point approach to determine an accurate dissociation energy of 1.35 kcal mol − 1 for the complex dissociating into water and O( 3 P). We also predict the anharmonic vibrational frequencies of the complex in anticipation of future experiments aimed at detecting this system.

Dual roles of Cu2+ complexation with dissolved organic matter on the photodegradation of trace organic pollutants: Triplet- and [rad]OH-induced reactions

The triplet excited state of dissolved organic matter (3DOM⁎) is highly effective in the photodegradation of a broad spectrum of trace organic pollutants (TOPs), and its photoactivity is affected by concomitant metal ions in surface waters. However, the impact of environmental metal ions on the 3DOM⁎-induced photodegradation of TOPs has not been systemically explored. Herein, we investigated the effect of environmental Cu2+ on the 3DOM⁎-induced photodegradation kinetics of 16 TOPs. A fluorescence quenching experiment showed that a Cu(II)-DOM complex was formed. For the TOPs with stronger electron-donating groups (triplet-labile moieties, e.g., phenols and anilines), Cu2+ complexation notably inhibited 3DOM⁎-induced photodegradation. This may be ascribed to the decrease of 3DOM⁎ steady-state concentration because Cu2+ complexation reduces its formation rates and enhances scavenging rates tested by sorbic acid isomerization experiment. Meanwhile, it was found that Cu2+ complexation facilitated the photolysis of refractory TOPs (lower triplet reactivity) because of enhanced electron transfer between DOM and Cu(II), causing photoinduced OH formation. These findings implied that 3DOM⁎ reactivity differences in TOPs could affect the photodegradation rates in the complex system, which was confirmed via a linear correlation of photodegradation rate ratios for 16 TOPs induced by 3DOM⁎ in the presence/absence of Cu2+ with their 3DOM⁎ reactivity. These findings helped to improve our understanding of the photochemical reactivity of 3DOM⁎ in natural waters, especially the effects of environmentally concomitant metal ions.

The effects of halogen substituents on structure, stability, and electronic properties of bicyclo[1.1.1]pentanylene at density functional theory

AbstractIn a quest to identify novel bicyclic carbenes, the effects of halogen substituents on the stability and reactivity of singlet (s) and triplet (t) forms of carbenes with one, two, and three carbenic centers (1‐15) are compared and contrasted, at B3LYP/6‐311++G** level of theory. All carbene scrutinized turn out as minima for showing no negative force constant on their energy surfaces. The highest stability (ΔEs‐t) and band gap (ΔEHOMO–LUMO) belongs to carbene 11 (37.36 and 133.45 kcal/mol, respectively) with three carbenic centers. Such higher stabilization attributed to three coordinate covalent bonds with their carbenic centers. The nucleophilicity (N) for each series (1‐5, 6‐10, and 11‐15) appears inverse correlation with our results of chemical potential (μ) values. Also, the N of the carbenic center is decreased due to the higher electronegativity of substituted halogens. In addition, the electrostatic potential (ESP) maps qualitatively confirm the relative N for our bicyclic carbenes.The aim of the present work was to assess the effects of halogen substituents on the stability (ΔEs‐t), ΔΕHOMO–LUMO, N, electrophilicity (ω), and proton affinity (ΔEPA). Finally, our investigation introduces carbene 1s with high stability (ΔEs‐t = 30.38 kcal/mol), N (3.438 eV), and negative ΔEPA (−244.94 kcal/mol) that can be applied as accumulated multidentate ligands.

A New Pathway for Intersystem Crossing: Unexpected Products in the O(3P) + Cyclopentene Reaction.

We investigated the reaction of O(3P) with cyclopentene at 4 Torr and 298 K using time-resolved multiplexed photoionization mass spectrometry, where O(3P) radicals were generated by 351 nm photolysis of NO2 and reacted with excess cyclopentene in He under pseudo-first-order conditions. The resulting products were sampled, ionized, and detected by tunable synchrotron vacuum ultraviolet radiation and an orthogonal acceleration time-of-flight mass spectrometer. This technique enabled measurement of both mass spectra and photoionization spectra as functions of time following the initiation of the reaction. We observe propylketene (41%), acrolein + ethene (37%), 1-butene + CO (19%), and cyclopentene oxide (3%), of which the propylketene pathway was previously unidentified experimentally and theoretically. The automatically explored reactive potential energy landscape at the CCSD(T)-F12a/cc-pVTZ//ωB97X-D/6-311++G(d,p) level and the related master equation calculations predict that cyclopentene oxide is formed on the singlet potential energy surface, whereas propylketene is first formed on the triplet surface. These calculations provide evidence that significant intersystem crossing can happen in this reaction not only around the geometry of the initial triplet adduct but also around that of triplet propylketene. The formation of 1-butene + CO is initiated on the triplet surface, with bond cleavage and hydrogen transfer occurring during intersystem crossing to the singlet surface. At present, we are unable to explain the mechanistic origins of the acrolein + ethene channel, and we thus refrain from assigning singlet or triplet reactivity to this channel. Overall, at least 60% of the products result from triplet reactivity. We propose that the reactivity of cyclic alkenes with O(3P) is influenced by their greater effective degree of unsaturation compared with acyclic alkenes. This work also suggests that searches for minimum-energy crossing points that connect triplet surfaces to singlet surfaces should extend beyond the initial adducts.

Investigation of fused remote N-heterocyclic silylenes (frNHSis), at DFT.

We compared and contrasted the ΔΕs-t, band gap (ΔΕHOMO-LUMO), aromaticity, charge distribution, and reactivity of singlet (s) and triplet (t) benzopyridine-4-ylidene as the fused remote N-heterocyclic carbene (frNHC) and frNHSis with different fused aromatic rings, at (U)B3LYP/AUG-cc-pVTZ and (U)M06-2X/AUG-cc-pVTZ levels of theory. In this investigation, we found (1) all s and t divalent states appear as minimum structures, for having no negative force constant. Nonetheless, only singlets present more thermodynamic stability than their triplet analogous; (2) the trend of ΔΕs-t in kcal/mol is ortho-pyrrole (52.94) > ortho-furan (51.84) > ortho-thiophene (50.38) > para-furan (49.36) > para-pyrrole (49.00) > para-phosphole (48.67) ≥ para-thiophene (48.64) > benzene (44.33) > ortho-phosphole frNHSi (27.50), while ΔΕs-t of frNHC is 15.65kcal/mol; (3) apart from phosphole frNHSis, the order of ΔΕs-t in a "ortho position or zigzag array" about 1.8-4.0kcal/mol is more than that of in a "para position or chair array"; (4) the highest ΔΕHOMO-LUMO is demonstrated by ortho-pyrrole frNHSi (95.65kcal/mol) while the lowest ΔΕHOMO-LUMO is verified by the reference frNHC (63.44kcal/mol); (5) in contradiction of frNHC, all singlet frNHSis reveal higher band gap and lower global reactivity than their triplet congeners; (6) charge distribution along with MEP maps indicate differentially electronic cloud in middle of rings frNHSis vs. frNHC; (7) we anticipate higher nucleophilicity and lower electrophilicity of triplet frNHSis than singlet congeners, will make them worthy of synthetic surveys.

Photocycloadditions of Arenes Derived from Lignin.

Intramolecular photocycloaddition reactions of 3,4-alkoxybenzonitriles derived from vanillin with alkenes have been investigated. In contrast to previous reports on photochemical reactions with these compounds, mainly [2 + 3] cycloaddition has been observed. A competing [2 + 2] photocycloaddition plays a minor role. Most probably, these additions occur at the singlet state S1. In the case of a triplet reaction, a different regioselectivity of the [2 + 2] cycloaddition would be observed. Linear and angular [2 + 3] cycloadducts are formed as major products. The first isomer is transformed in the second one by a photochemical vinyl-cyclopropane rearrangement, which increases the selectivity of the reaction. The influence of the substitution pattern on the reactivity and the selectivity has also been investigated.

Structure-Dependent Electron Transfer Rates for Dihydrophenazine, Phenoxazine, and Phenothiazine Photoredox Catalysts Employed in Atom Transfer Radical Polymerization.

Organic photocatalysts (PCs) are gaining popularity in applications of photoredox catalysis, but few studies have explored their modus operandi. We report a detailed mechanistic investigation of the electron transfer activation step of organocatalyzed atom transfer radical polymerization (O-ATRP) involving electronically excited organic PCs and a radical initiator, methyl 2-bromopropionate (MBP). This study compares nine N-aryl modified PCs possessing dihydrophenazine, phenoxazine, or phenothiazine core chromophores. Transient electronic and vibrational absorption spectroscopies over subpicosecond to nanosecond and microsecond time intervals, respectively, track spectroscopic signatures of both the reactants and products of photoinduced electron transfer in N,N-dimethylformamide, dichloromethane, and toluene solutions. The rate coefficients for electron transfer exhibit a range of values up to ∼1010 M-1 s-1 influenced systematically by the PC structures. These rate coefficients are an order of magnitude smaller for catalysts with charge transfer character in their first excited singlet (S1) or triplet (T1) states than for photocatalysts with locally excited character. The latter species show nearly diffusion-limited rate coefficients for the electron transfer to MBP. The derived kinetic parameters are used to model the contributions to electron transfer from the S1 state of each PC for different concentrations of MBP. Comparisons of singlet and triplet reactivity for one of the phenoxazine PCs reveal that the rate coefficient kET(T1) = (2.7 ± 0.3) × 107 M-1 s-1 for electron transfer from the T1 state is 2 orders of magnitude lower than that from the S1 state, kET(S1) = (2.6 ± 0.4) × 109 M-1 s-1. The trends in bimolecular electron transfer rate coefficients are accounted for using a modified Marcus theory for dissociative electron transfer.

Non-isothermal crystallization kinetics of Ge-Cu-Te thin films for phase-change memory

We investigated the crystallization kinetics of Ge-Cu-Te ternary system phase-change thin films using non-isothermal differential scanning calorimetry and estimated the kinetic triplet (activation energy, pre-exponential factor, and reaction model) by the combined application of isoconversional and model-fitting approaches at different heating rates over a range of 10–40 K/min for GeCu2Te2 thin films. The results indicate a multi-step crystallization process where the activation energy of crystallization is not constant but decreases via three recognizable stages with crystallization fraction α. The local Avrami exponents suggest that two crystallization mechanisms containing three-dimensional growth with increasing nucleation rates in the range of crystallization fraction α ≤ 0.4 and three- and two-dimensional growths at a decreasing nucleation rate over the wide range of α > 0.4 are responsible for the whole crystallization process. Furthermore, the reaction model displays dependence on the heating rates for the GeCu2Te2 thin films, where heating rates of 10–30 K/min drive a second-order reaction while a three-halve order reaction occurs for a heating rate of 40 K/min, which is different from the second-order reaction for the GeCu2Te3 thin films. Also, both GeCu2Te2 and GeCu2Te3 thin films provide better data retention capability than the Ge2Sb2Te5 thin films without sacrificing the crystallization time. The results indicate that Ge-Cu-Te ternary system thin films have great potentiality in phase-change memory applications.

Kinetics and Mass Yields of Aqueous Secondary Organic Aerosol from Highly Substituted Phenols Reacting with a Triplet Excited State.

Biomass burning emits large amounts of phenols, which can partition into cloud/fog drops and aerosol liquid water (ALW) and react to form aqueous secondary organic aerosol (aqSOA). Triplet excited states of organic compounds (3C*) are likely oxidants, but there are no rate constants with highly substituted phenols that have high Henry's law constants (KH) and are likely important in ALW. To address this gap, we investigated the kinetics of six highly substituted phenols with the triplet excited state of 3,4-dimethoxybenzaldehyde. Second-order rate constants at pH 2 are all fast, (2.6-4.6) × 109 M-1 s-1, while values at pH 5 are 2-5 times smaller. Rate constants are reasonably described by a quantitative structure-activity relationship with phenol oxidation potentials, allowing rate constants of other phenols to be predicted. Triplet-phenol kinetics are unaffected by ammonium sulfate, sodium chloride, galactose (a biomass-burning sugar), or Fe(III). In contrast, ammonium nitrate increases the rate of phenol loss by making hydroxyl radicals, while Cu(II) inhibits phenol decay. Mass yields of aqueous SOA from triplet reactions are large and range from 59 to 99%. Calculations using our data along with previous oxidant measurements indicate that phenols with high KH can be an important source of aqSOA in ALW, with 3C* typically the dominant oxidant.

Substituent Effect On Structure, Stability, and Electronic Properties of the Novel Bicyclic Silylenes at DFT

The density functional theory (DFT) calculations are carried out to assay the effects of nitrogen atoms on the stability and reactivity of singlet (s) and triplet (t) forms of novel silylenes with one, two, and three silylene centers (1s-18s and 1t-18t, receptively) at B3LYP/6-311 + + G** level of theory. Every one of the 36 silylenes scrutinized appears as minimum on its energy surface, for showing no negative force constant. All of our silylenes have singlets ground state and the highest stability belongs to silylene 2 (ΔEs−t = 44.71.95 kcal/mol). This clearly demonstrates the effect of intermolecular interactions ( $$\sigma$$ (C(E and G)−H(exo))→LP*Si). The aim of the present work was to consider the influence of nitrogen substituents on the stability (ΔEs−t), band gap (ΔEHOMO−LUMO), nucleophilicity (N), electrophilicity (ω), and isodesmic reactions. Finally, our investigation offers new insights into the chemistry of novel bicyclic silylenes that can be applied as cumulated multi-dentate ligands. We have compared and contrasted the substituent effects on the stability and reactivity of singlet (s) and triplet (t) forms of novel silylenes with one, two, and three silylene centers (1s-18s and 1t-18t, receptively) at B3LYP/6-311 + + G** level of theory. All novel silylenes show singlet ground state and the highest stability belongs to silylene 2 (ΔEs−t = 44.71.95 kcal/mol). This stability can be related to its intermolecular interactions. The nonbonding electrons at the nitrogens (E or G) of silylenes 3s, 5s, 6s, 7s, 8s, 9s, 11s, 14s and 15s appear to have a tendency to interact with the empty p orbital of the silylene center and form a σ-bond.

Genetic etiologic analysis in 74 Chinese Han women with idiopathic premature ovarian insufficiency by combined molecular genetic testing.

To identify the disease-causing genes of Chinese Han women with idiopathic premature ovarian insufficiency (POI). Seventy-four Chinese Han women with idiopathic POI were collected to analyze the genetic etiology. Triplet repeat-primed polymerase chain reaction (TP-PCR) was performed to screen the FMR1 (CGG)n premutation, and then 60 POI-related genes were sequenced by targeted next-generation sequencing (NGS) in POI patients with normal FMR1. A total of one patient (1/74) with FMR1 premutation was identified. Targeted NGS revealed that 15.07% (11/73) patients had pathogenic or likely pathogenic variants of Mendelian genes (FOXL2, EIF2B2, CYP17A1, CLPP, MCM9, GDF9, MSH5, ERCC6, POLG). Ten novel variants in six Mendelian genes were identified, such as CLPP c.355A>C (p.I119L) and c.688A>C (p.M230L), MCM9 c.1157C>T (p.T386M) and c.1291A>G (p.M431V), GDF9 c. 238C>T (p.Q80X), MSH5 c.604G>C (p.G202R) and c.2063T>C (p.I688T), ERCC6 c.C1769C>T (p.P590L), POLG c.2832G>C (p.E944D), and c.2821A>G (p.I941V). This study suggested targeted NGS was an efficient etiologic test for idiopathic POI patients without FMR1 premutation and enriched the variant spectrum of POI-related genes.