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Electron detachment dissociation (EDD), recently introduced by Zubarev and co-workers for the dissociation of multiply charged biomolecular anions via a radical ion intermediate, has been shown to be analogous to electron capture dissociation (ECD) in several respects, including more random peptide fragmentation and retention of labile posttranslational modifications. We have previously demonstrated unique fragmentation behavior in ECD compared to vibrational excitation for oligodeoxynucleotide cations. However, that approach is limited by the poor sensitivity for oligonucleotide ionization in positive ion mode. Here, we show implementation of EDD on a commercial Fourier transform ion cyclotron resonance mass spectrometer utilizing two different configurations: a heated filament electron source and an indirectly heated hollow dispenser cathode electron source. The dispenser cathode configuration provides higher EDD efficiency and additional fragmentation channels for hexamer oligodeoxynucleotides. As in ECD, even-electron d/w ion series dominate the spectra, but we also detect numerous a/z (both even-electron and radical species), (a/z - B), c/x, (c/x - B), and (d/w - B) ions with minimal nucleobase loss from the precursor ions. In contrast to previous high-energy collision-activated dissociation (CAD) and ion trap CAD of radical oligonucleotide anions, we only observe minimum sugar cross-ring cleavage, possibly due to the short time scale of EDD, which limits secondary fragmentation. Thus, EDD provides fragmentation similar to ECD for oligodeoxynucleotides but at enhanced sensitivity. Finally, we show that noncovalent bonding in a DNA duplex can be preserved following EDD, illustrating another analogy with ECD. We believe the latter finding implies EDD has promise for characterization of nucleic acid structure and folding.

A study was conducted to analyze the synthesis of a C2-symmetric bistetrahydrofuran core of acetogenins by double intramolecular S(sub N') O-cyclization reactions. Sharpless asymmetric dihydroxylation was utilized to carry out the analysis. Results indicated that novel terminal double bonds can be utilized as functional groups for the stepwise elaboration to secondary hydroxyl derivatives.

Long-standing challenges to simultaneouslyaccomplish crystal-likeelectrical transport and glass-like thermal transport in materialshinder the development of thermoelectric energy conversion technologies.We show that the unusual combination of these transport propertiescan be realized in electron-poor II–V semiconductor CdSb. Anisotropicmulticenter bonding in CdSb is essential to both electrical and thermaltransport. The electron-deficiency-sharing multicenter interactionslead to low overall ionicity and hence relatively high carrier weightedmobility and power factor. The bond anisotropy causes large latticeanharmonicity, which coupled with low cutoff frequency of the longitudinalacoustic branch and low sound velocity, gives rise to intrinsicallylow lattice thermal conductivity, approaching the glass-limit at elevatedtemperatures. A maximum thermoelectric figure of merit ZTof ∼1.3 at 560 K and an average ZTof 1.0between 300 K and 600 K are achieved for the 0.5 at. % Ag-doped sample,which makes CdSb an attractive candidate for low-intermediate temperatureor multistage power generations. Our study advocates the search forhigh efficiency thermoelectric materials in compounds with anisotropictwo- and multicenter bonding. [ABSTRACT FROM AUTHOR]

The putative structure of cytotoxic diterpenoid (-)-sclerophytin A and of the authentic natural sclerophytins A and B was synthesized.

With the development of new synthesis procedures, an ever increasing number of chemical modifications can now be incorporated into synthetic oligonucleotides, representing new challenges for analytical chemists to efficiently identify and characterize such molecules. While conventional mass spectrometry (MS) has proven to be a powerful tool to study nucleic acids, new and improved methods and software are now needed to address this emerging challenge. In this report, we describe a simple yet powerful program that affords great flexibility in the calculation of theoretical masses for conventional as well as modified oligonucleotide molecules. This easy to use program can accept input oligonucleotide sequences and then calculate the theoretical mass values for full length products, process impurities, potential metabolites, and gas phase fragments. We intentionally designed this software so that modified nucleotide residues can be incorporated into oligonucleotide sequences, and corresponding mass values can be rapidly calculated. To test the utility of this program, two oligonucleotides that contain a large number of chemical modifications were synthesized. We have analyzed these samples using a Q-TOF mass spectrometer and compared the calculated masses to the observed ones. We found that all of the data matched very well with less than 30 ppm mass errors, well within the expectation for our instrument operated in its current mode. These data confirmed the validity of calculations performed with this new software. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We have recently demonstrated that both electron capture dissociation (ECD) and electron detachment dissociation (EDD) can provide complementary sequence-specific cleavage of DNA compared with collision activated dissociation (CAD) and infrared multiphoton dissociation (IRMPD). However, EDD is preferred because of more extensive fragmentation at higher sensitivity (due to its negative ion mode operation). Here, we extend the radical ion chemistry of these two gas-phase ion-electron reaction techniques to the characterization of RNA. Compared with DNA, rather limited information is currently available on the gas-phase fragmentation of RNA. We found that the ECD fragmentation patterns of the oligoribonucleotides A6, C6, and CGGGGC are nucleobase dependent, suggesting that cleavage proceeds following electron capture at the nucleobases. Only limited backbone cleavage was observed in ECD. EDD, on the other hand, provided complete sequence coverage for the RNAs A6, C6, G6, U6, CGGGGC, and GCAUAC. The EDD fragmentation patterns were different from those observed with CAD and IRMPD in that the dominant product ions correspond to d- and w-type ions rather than c- and y-type ions. The minimum differences between oligoribonucleotides suggest that EDD proceeds following direct electron detachment from the phosphate backbone. [Copyright &y& Elsevier]

Metalo hydrogen-bonded organic frameworks (MHOFs) have received growing interest in designing crystalline functional materials. However, reports on bifunctional MHOFs showing magnetic and proton-conductive properties are extremely limited and their design is challenging. Herein, we investigated the magnetic and proton-conductive properties of two sulfonated CoHOF and MnHOF , {M(H 2 O) 2 (abs) 2 } n (M = Co 2+ and Mn 2+ , Habs = 4-aminoazobenzene-4'-sulfonic anion), constructed by coordination chains. The supramolecular frameworks sustained by H bonds between -SO 3 - and coordinated water show directional ladder-type H bonds with hydrophilic nanochannels, leading to high proton conduction with exceptionally high conductivity around 10 -2 S cm -1 at 100 °C under 97% relative humidity. In particular, the maximum σ value of CoHOF , 2.11 × 10 -2 S cm -1 , recorded the highest value among the reported proton-conducting materials showing slow magnetic relaxation. Meanwhile, the molecular structure of organosulfonate enables the magnetic isolation of high-spin Co 2+ and Mn 2+ centers in the frameworks. Magnetic measurements indicated that the MHOFs show field-induced single-ion magnet (SIM) properties, making these compounds rare magnetic-proton-conductive MHOFs. The work provides not only two unique MHOFs with SIM behavior and high proton conduction performance but also avenues for designing stable bifunctional MHOFs via a coordination chain approach.

Extending a selected cyanometalate block into a higher dimensional framework continues to present intriguing challenges in the fields of chemistry and material science. Here, we prepared two rope-like chain compounds of {[(Tp* Me )Fe(CN) 3 ] 2 Cu 2 X 2 (L)}·sol ( 1 , X = Cl, L = (MeCN) 0.5 (H 2 O/MeOH) 0.5 , sol = 2MeCN·1.5H 2 O; 2 , X = Br, L = MeOH, sol = 2MeCN·0.75H 2 O; Tp* Me = tris(3, 4, 5-trimethylpyrazole)borate) in which the cyanide-bridged trigonal-bipyramidal [Fe 2 Cu 3 ] subunits were linked with the adjacent ones via two vertex Cu(II) centers, providing a new cyanometallate chain archetype. Direct current magnetic study revealed the presence of ferromagnetic couplings between Fe(III) and Cu(II) ions and uniaxial anisotropy due to a favorable alignment of the anisotropic tricyanoiron(III) units. Moreover, compound 1 exhibits single-chain magnet behavior with an appreciable energy barrier of 72 K, while 2 behaves as a metamagnet, likely caused by the subtle changes in the interchain interactions.

Thermoelectric (TE) materials can directly convert heat to electricity and vice versa and have broad application potential for solid-state power generation and refrigeration. Over the past few decades, efforts have been made to develop new TE materials with high performance. However, traditional experiments and simulations are expensive and time-consuming, limiting the development of new materials. Machine learning (ML) has been increasingly applied to study TE materials in recent years. This paper reviews the recent progress in ML-based TE material research. The application of ML in predicting and optimizing the properties of TE materials, including electrical and thermal transport properties and optimization of functional materials with targeted TE properties, is reviewed. Finally, future research directions are discussed.

The incorporation of two different cyanide building blocks of [(Tp R )Fe III (CN) 3 ] - and [Au I (CN) 2 ] - into one molecule afforded a novel hexanuclear [Fe III 2 Fe II 2 Au I 2 ] complex ( 1·2Et 2 O ), in which the cyanide-bridged [Fe III 2 Fe II 2 ] square was further grafted by two [Au I (CN) 2 ] - fragments as long arms in syn orientations. Complex 1·2Et 2 O undergoes a gradual spin crossover (SCO) ffrom low-spin (LS) to high-spin (HS) state for the Fe(II) centers upon desolvation. Remarkably, its desolvated phase ( 1 ) exhibits a reversible but atypical two-step (sharp-gradual) SCO behavior with considerable hysteresis (21 K). Variable-temperature single-crystal X-ray structural studies reveal that the hysteretic spin transition takes place synchronously with the concerted displacive motions of the molecules, representing another rare example including multistep and hysteretic spin transitions due to the synergetic SCO and structural phase transition.

Low melting point eutectic systems, such as the eutectic gallium-indium (EGaIn) alloy, offer great potential in the domain of nanometallurgy; however, many of their interfacial behaviors remain to be explored. Here, a compositional change of EGaIn nanoalloys triggered by polydopamine (PDA) coating is demonstrated. Incorporating PDA on the surface of EGaIn nanoalloys renders core-shell nanostructures that accompany Ga-In phase separation within the nanoalloys. The PDA shell keeps depleting the Ga 3+ from the EGaIn nanoalloys when the synthesis proceeds, leading to a Ga 3+ -coordinated PDA coating and a smaller nanoalloy. During this process, the eutectic nanoalloys turn into non-eutectic systems that ultimately result in the solidification of In when Ga is fully depleted. The reaction of Ga 3+ -coordinated PDA-coated nanoalloys with nitrogen dioxide gas is presented as an example for demonstrating the functionality of such hybrid composites. The concept of phase-separating systems, with polymeric reservoirs, may lead to tailored materials and can be explored on a variety of post-transition metals.

The successful introduction of azide ions as secondary bridges into the Fe III -Ni II cyanide system afforded two clusters and one unique 4(3),2-ribbon chain: [(bpzpy) 2 Ni 2 (μ 2 -1,1-N 3 ) 2 {(pzTp)Fe(CN) 3 } 2 ]·3H 2 O [ 1 ; bpzpy = 2,6-bis(pyrazol-1-yl)pyridine, and pzTp = tetrakis(pyrazolyl)borate], [(L1) 2 Ni 4 (μ 3 -1,1,1-OCH 3 ) 2 (μ 2 -1,1-N 3 ) 2 (H 2 O) 2 {(Tp)Fe(CN) 3 } 2 ]·2CH 3 OH·H 2 O [ 2 ; Tp = hydrotris(pyrazolyl)borate, and HL1 = 2,6-bis{(2-hydroxypropylimino)methyl}-4-methylphenol], and [(L2) 2 Ni 3 (μ 2 -1,1-N 3 ) 4 {(pzTp)Fe(CN) 3 } 2 ] n ( 3 ; L2 = 2-{[phenyl(pyridin-2-yl)methylene]amino}ethan-1-amine). Both 1 and 2 feature the centrosymmetric {Fe III -Ni II 2 -Fe III } and {Fe III -Ni II 4 -Fe III } rodlike structures in which the two peripheral [(Tp R )Fe(CN) 3 ] - anions act as monodentate ligands via one cyanide group to link the central azide-bridged [Ni 2 ] and [Ni 4 ] subunit, respectively, while 3 displays an extended structure of the double-zigzag (4,2-ribbon) chain in which the double end-on azide-bridged trinuclear [Ni 3 ] subunits serve as the 4-connected nodes. Magnetic study revealed that intramolecular ferromagnetic coupling is dominated by the azide or cyanide bridges in all of the complexes. Remarkably, complex 1 behaves as a single-molecule magnet with an effective energy barrier of 16.5 cm -1 at zero dc field, while complex 3 exhibits metamagnetism with a hidden spin canting property below 12 K.

AgSbSe 2 is a typical member of cubic I-V-VI 2 semiconductors, which are known for their extremely low lattice thermal conductivity (κ l ). However, the low electrical conductivity of AgSbSe 2 , below ∼10 S cm -1 at room temperature, has hindered its thermoelectric performance. In this work, single-phase AgSbSe 2 bulk samples with much higher electrical conductivity were synthesized via self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) for the first time. Pb doping through the nonequilibrium process further increases the electrical conductivity to >100 S cm -1 . Furthermore, continuously increased effective mass m d * can be achieved upon Pb doping because of the multiple degenerate valence bands of AgSbSe 2 and the energy-filtering effect induced by in situ -formed nanodots. The simultaneous enhancement of both the electrical conductivity and Seebeck coefficient contributes to an unprecedentedly high average power factor of 6.75 μW cm -1 K -2 . Meanwhile, the introduced dense grain boundaries and point defects enhance the phonon scattering and consequently suppress κ l , yielding a high ZT value of 1.2 at 723 K in AgSb 0.94 Pb 0.06 Se 2 . This study opens a new avenue for rapid, low-cost, large-scale production of AgSbSe 2 -based materials and demonstrates that Pb-doped AgSbSe 2 prepared via the SHS-SPS method is a promising candidate for thermoelectric applications.

In this work, we report a series of Cu 3 R Te 3 ( R = Y, Sm, and Dy) ternary compounds with a trigonal structure ( R 3̅) as a family of new thermoelectric materials. First-principles calculations show that Cu 3 R Te 3 ( R = Y, Sm, and Dy) compounds are semiconductors with similar band structures and moderate band gaps (0.69-0.82 eV). The synthesized polycrystalline Cu 3 R Te 3 ( R = Y, Sm, and Dy) compounds possess moderate carrier concentrations (0.8-2.2 × 10 20 cm -3 ) and density-of-state effective masses (around 1.1 m e ), yielding decent electrical transport performance. Furthermore, intrinsically low lattice thermal conductivities, below 1 W m -1 K -1 at 300-900 K, originating from the heavy average atomic masses and large number of atoms in the unit cell, are observed for Cu 3 R Te 3 ( R = Y, Sm, and Dy). Finally, Cu 3 DyTe 3 demonstrates a peak dimensionless figure of merit of 0.9 at 900 K, which is among the highest reported for the Cu/Ag-based tellurides.

There is a strong demand for developing tunable and facile routes for synthesizing gas-sensitive semiconducting compounds. The concept of synthesizing micro- and nanoparticles of metallic compounds in a tunable process, which relies on liquid metals, is presented here. This is a liquid-based ultrasonication procedure within which additional metallic elements (In, Sn, and Zn) are incorporated into liquid Ga that is sonicated in a secondary solvent. We investigate liquid metal sonication in dimethyl sulfoxide (DMSO) and water to show their impact on the size, morphology, and crystal structure of the particulated products. The synthesized materials are annealed to investigate their responses to model reducing (H 2 ) and oxidizing (NO 2 ) gas species. The preparation process in DMSO gives rise to predominantly monoclinic Ga 2 O 3 crystals which are favorable for gas sensing, while the emergence of rhombohedral Ga 2 O 3 phases from the water sonication process led to inactive samples. The ease of tunability without hazardous precursors during the synthesis procedure is demonstrated. The route presented here can be uniquely employed for designing and engineering on-demand functional materials for sensing applications.

β-FeSi 2 has long been investigated as a promising thermoelectric (TE) material working at high temperatures due to its combining features of environmental friendliness, good thermal stability, and strong oxidation resistance. However, the real application of β-FeSi 2 is still limited by its low TE figure of merit ( zT ). In this study, nearly doubled zT in p-type β-FeSi 2 has been achieved via synergistically optimizing electrical and thermal transports. Based on the first-principles calculations, Al with shallow acceptor transition level and high carrier donation efficiency is chosen to dope β-FeSi 2 . Significantly improved electrical transport, particularly in the low temperature range, has been obtained in the Al-doped β-FeSi 2 system. The power factor for FeSi 1.96 Al 0.04 at 300 K is even higher than that of p-type β-FeSi 2 -based compounds reported previously at high temperatures. By alloying β-FeSi 2 with Os at the Fe sites, we further lower the lattice thermal conductivity. Fe 0.80 Os 0.20 Si 1.96 Al 0.04 possesses the lowest lattice thermal conductivity among the β-FeSi 2 compounds prepared by the equilibrium method. Finally, a record-high zT value of 0.35 is obtained for p-type Fe 0.80 Os 0.20 Si 1.96 Al 0.04 . This study is expected to accelerate the application of β-FeSi 2 .