Selenium Atoms Research Articles

Peroxynitrite Sensing Using Electrode Interfaces Decorated with Grafted Diaryl Selenides

Peroxynitrite is a highly reactive species that is known to cause damage to cells, and it is challenging to measure its concentration accurately. Electrochemical methods for detecting peroxynitrite are limited, and there is ongoing research to develop effective electrochemical probes or catalytic materials that can serve as interfaces for efficient detection of peroxynitrite. In our previous work we developed and characterized a thin film material based on 4,4’ diaminodiphenyl selenide grafted onto glassy carbon electrodes to create a functional interface for peroxynitrite detection. This selenide-based peroxynitrite sensors demonstrated remarkable sensitivity and a low limit of detection, and we postulated an electrocatalytic catalytic mechanism whereby the grafted selenide moieties act as electroactive mediators that ultimately lead to the catalytic oxidation of peroxynitrite. The positive charge developed on the selenium atom of the diarylselenide upon electrochemical oxidation is crucial for a such electrocatalytic mechanism. To test the validity of the postulated mechanism, we designed other other diarylselenides with different functional groups in the para position of the selenium atom. In this study, we decorated electrodes with diarylselenide moieties bearing various functional groups in the para position of the selenium atom of the diaryl selenide (See Scheme1; R=-H, -OMe, -CF3).We show that the electron-withdrawing -CF3 group significantly improves the sensitivity of the corresponding electrode towards PON. The opposite is observed with the methoxy group, which almost abolishes the mediated electrocatalytic oxidation of PON. We will present the results and analyze these findings in light of the electron-donating or withdrawing ability of the substituents placed in the para position from the selenium atom in the context of the postulated electrocatalytic mechanism mediated by the selenide moiety.

Efficient Regioselective Synthesis of Novel Ensembles of Organylselanyl-Functionalized Divinyl Sulfides and 1,3-Thiaselenoles under Phase Transfer Catalysis Conditions

Efficient regioselective synthesis of novel ensembles of organylselanyl-functionalized 1,3-thiaselenoles and divinyl sulfides in high yields under phase transfer catalysis conditions was developed. The methodology is based on the generation of sodium [(Z)-2-(vinylsulfanyl)ethenyl]selenolate and 1,3-thiaselenol-2-ylmethylselenolate, which were involved in a nucleophilic addition reaction with activated alkenes such as acrylonitrile, acrylamide, methyl vinyl ketone, methyl, and ethyl acrylates. In the case of methyl vinyl ketone, the reaction was accompanied by the hydrogenation of the carbonyl group. Methylene chloride was involved in the nucleophilic substitution reaction with sodium [(Z)-2-(vinylsulfanyl)ethenyl]selenolate and 1,3-thiaselenol-2-ylmethylselenolate to afford new polyunsaturated compounds with several sulfur and selenium atoms.

Recent Advances in Design and Synthesis of 1,3-Thiaselenolane and 1,3-Thiaselenole Derivatives

Recent advances in the design and synthesis of five-membered heterocycles containing both sulfur and selenium atoms—1,3-thiaselenolane and 1,3-thiaselenole derivatives—are discussed in this review. These heterocyclic systems are of interest as intermediates for organic synthesis and compounds that can exhibit various useful properties, including biological activity and electrical conductivity. The main focus of the review is on the works of the last 20 years that make use of catalytic reactions. Synthetic methods for the preparation of structurally related 1,4,5,8-diselenadithiafulvalenes based on catalytic cross-coupling reactions are also presented. To date, the design and synthesis of 1,3-thiaselenolane and 1,3-thiaselenole derivatives have not been discussed in a separate review.

Organoselenium compounds. Chemistry and applications in organic synthesis.

Selenium, originally described as a toxin, turns out to be a crucial trace element for life that appears as selenocysteine and its dimer, selenocystine. From the point of view of drug developments, selenium-containing drugs are isosteres of sulfur and oxygen with the advantage that the presence of the selenium atom confers antioxidant properties and high lipophilicity, which would increase cell membrane permeation leading to better oral bioavailability. In this article we have focused on the relevant features of the selenium atom, above all, the corresponding synthetic approaches to access a variety of organoselenium molecules along with the proposed reaction mechanisms. The preparation and biological properties of selenosugars, including selenoglycosides, selenonucleosides, selenopeptides, and other selenium-containing compounds will be treated. We have attempted to condense the most important aspects and interesting examples of the chemistry of selenium into a single article.

Influence of S-content ratios on the defect properties of Sb2(Sx, Se1–x)3 thin-film solar cells

Sb2(S, Se)3 has widely emerged as an absorber material for solar cells because of its favourable optical properties and abundant raw materials. Although the Sb2(S, Se)3 film comprises simple binary elements and has a lesser complex phase than that of quaternary copper indium gallium selenide, the distribution of atoms within its structure significantly affects its performance. More specifically, this effect is attributed to three non-equivalent positions of selenium or sulphur atoms and two non-equivalent positions of antimony atoms inside its unique quasi-one-dimensional asymmetric structure. Consequently, the composition ratios inside Sb2(Sx, Se1–x)3 significantly impact the film's properties, especially the defect properties. The underlying origins of this effect remain elusive. Along these lines, in this work, defect measurements of the Sb2(Sx, Se1–x)3 solar cells with different S-content ratios were conducted using deep-level transient spectroscopy and then discussed in detail. The analysis confirmed that deep-level defects were always present, and their lower density favoured the device's performance. Moreover, the solar cells consisting of Sb2(Sx, Se1–x)3 thin films with 0.3 S-content ratios exhibit better conversion efficiency with lower deep-level defects density and capture cross-section.

Tetra-μ3-selen-ido-1:2:3κ3Se;1:2:4κ3Se;1:3:4κ3Se;2:3:4κ3Se-tetrakis-[(η5-methyl-cyclo-penta-dien-yl)molybdenum(III)](6 Mo-Mo).

The title cluster compound, [Mo4(η5-C5H4Me)4(μ3-Se)4], was synthesized from the reaction of [Mo(η5-C5H4Me)(CO)3]2 with grey selenium in refluxing xylene solution under a nitro-gen atmosphere. The complete cluster is generated by a crystallographic twofold axis and contains an Mo4Se4 cubane-like core surrounded by four η5-methylcyclo-pentadienyl ligands. In the core, the four molybdenum atoms are connected to each other to form a tetra-hedron, with a selenium atom capping each face. The Mo-Mo bond lengths vary from 2.9857 (5) to 3.0083 (3) Å and the Mo-Se separations range from 2.4633 (4) to 2.4693 (5) Å.

Strain Anisotropy Driven Spontaneous Formation of Nanoscrolls from 2D Janus Layers

Abstract2D Janus transition metal dichalcogenides (TMDs) have attracted attention due to their emergent properties arising from broken mirror symmetry and self‐driven polarization fields. While it has been proposed that their vdW superlattices hold the key to achieving superior properties in piezoelectricity and photovoltaic, available synthesis has ultimately limited their realization. Here, the first packed vdW nanoscrolls made from Janus TMDs through a simple one‐drop solution technique are reported. The results, including ab initio simulations, show that the Bohr radius difference between the top sulfur and the bottom selenium atoms within Janus (M = Mo, W) results in a permanent compressive surface strain that acts as a nanoscroll formation catalyst after small liquid interaction. Unlike classical 2D layers, the surface strain in Janus TMDs can be engineered from compressive to tensile by placing larger Bohr radius atoms on top (to yield inverted C scrolls. Detailed microscopy studies offer the first insights into their morphology and readily formed Moiré lattices. In contrast, spectroscopy and FETs studies establish their excitonic and device properties and highlight significant differences compared to 2D flat Janus TMDs. These results introduce the first polar Janus TMD nanoscrolls and introduce inherent strain‐driven scrolling dynamics as a catalyst to create superlattices.

Single selenium atom to control nucleic acid conformation and large crystal growth

Single selenium atom to control nucleic acid conformation and large crystal growth

Crystal structure of selenium-substituted acetylacetonates of boron difluoride

The molecular and crystal structure of boron difluoride acetylacetonates containing selenophenyl (1), diselenide (2) and selenocyanate groups (3) at the central carbon atom (γ) has been determined. As a result of comparing the structure of selenium- and sulfur-substituted complexes, it is shown that the replacement of a sulfur atom with a selenium atom practically does not change the relative position of substituents and chelate cycles, as well as the values of the main angles. The packing of complexes 2 and 3 in crystals repeats the packing of sulfur-containing analogues. For phenyl-substituted selenide and sulfide, the crystals are not isostructural. In the diselenide complex 2 molecules crystallize in pairs with one chelate cycle of each molecule participating in pair formation. The pairs are linked by an interaction similar to the stacking interaction. The second chelate cycle of each molecule in the pair does not participate in intermolecular interactions. In the acetylacetonate complexes studied, the chelate rings are not planar. These cycles have a “boat” conformation. The magnitude of bending of the cycle is determined by intermolecular interactions.

Green Organoselenium Chemistry: Selective Syntheses of New 1,4-Thiaselenine Derivatives Based on Reactions of Thiaselenole Reagent with Alcohols and Water

Environmentally friendly synthetic methods were developed for the selective preparation of new 2,3-dihydro-1,4-thiaselenine derivatives in high yields based on the reactions of 2-bromomethyl-1,3-thiaselenole with alcohols and water at room temperature. The reaction of 2-bromomethyl-1,3-thiaselenole with alcohols was accompanied by a rearrangement with ring extension, leading to six-membered heterocyclic compounds, a new family of 2-organyloxy-2,3-dihydro-1,4-thiaselenines, in 80–96% yields. The remarkable cascade reactions of 2-bromomethyl-1,3-thiaselenole with water afforded 2,3-dihydro-1,4-thiaselenines functionalized with the (Z)-S-CH=CH-Se fragment and one or two highly reactive aldehyde groups. The latter aldehydes were functionalized by the reactions with alcohols and glycols to give new polyfunctionalized compounds, containing two double bonds, two sulfur atoms, two selenium atoms, and two or four oxygen atoms, in high yields.

Trichalcogenasupersumanenes and its concave-convex supramolecular assembly with fullerenes

Synthesis of buckybowls have stayed highly challenging due to the large structural strain caused by curved π surface. In this paper, we report the synthesis and properties of two trichalcogenasupersumanenes which three chalcogen (sulfur or selenium) atoms and three methylene groups bridge at the bay regions of hexa-peri-hexabenzocoronene. These trichalcogenasupersumanenes are synthesized quickly in three steps using an Aldol cyclotrimerization, a Scholl oxidative cyclization, and a Stille type reaction. X-ray crystallography analysis reveals that they encompass bowl diameters of 11.06 Å and 11.35 Å and bowl depths of 2.29 Å and 2.16 Å for the trithiasupersumanene and triselenosupersumanene, respectively. Furthermore, trithiasupersumanene derivative with methyl chains can form host-guest complexes with C60 or C70, which are driven by concave-convex π ⋯ π interactions and multiple C–H ⋯ π interactions between bowl and fullerenes.

Morphological Effects on the Performance of Broadband Organic Photomultiplication Photodetectors Containing Selenium Substituted Non‐Fullerene Acceptors

AbstractOrganic photodetectors (OPDs) with spectral response extending from ultraviolet to near‐infrared domains are of great interest for many applications. Morphological impact on the performance of photomultiplication (PM)‐type OPDs, however, is still rarely investigated so far. Herein, a non‐fullerene acceptor, Y6‐Se‐HD, is synthesized, in which heavier selenium atoms substitute the sulfur atoms in the core of Y6, and used for fabricating PM‐OPDs. The resulting devices exhibit remarkable PM effects in a very broadband spectral range covering from 320 to 1090 nm. A maximum EQE value of ≈6500% at 860 nm is achieved at a low bias of −1.0 V. As compared with the device prepared with Y6 molecules, the Y6‐Se‐HD OPDs exhibited much enhanced performance. From the morphological analysis, we infer that Y6‐Se‐HD almost covers the entire active layer and avoids the direct contact of the hole‐trapping donor polymers with the Ag electrode, thereby resulting in stronger charge trapping and preventing possible charge recombination and/or quenching. Furthermore, finer phase separation between the donor and acceptor molecules also facilitates hole trapping and strengthens the PM effects. This research highlights the importance of morphological effects on the PM‐OPDs and demonstrates one approach for controlling the device morphology.

THE CRYSTAL STRUCTURE OF La3Pb0.1Ga1.6Se7 AND Pr3Pb0.1Ga1.6Se7 COMPOUNDS

Samples of the stoichiometric composition La3Pb0.1Ga1.6Sе7 and Pr3Pb0.1Ga1.6Sе7, weighing 0.8 gram each, were prepared by fusing components of semiconductor purity in vacuumed quartz containers to a residual pressure of 10-2 Pa. The synthesis was carried out in a muffle furnace with software control of MP-30 technological processes. The maximum temperature of synthesis is 1100°C, homogenizing annealing lasted 240 hours at temperature of 500°C.
 The diffraction patterns for X-ray phase analysis were recorded at a DRON 4-13 diffractometer for 2Q range of 10-100° (CuKα radiation, scan step 0.02°, 20 s exposure in each point). Data processing and the determination of the crystal structure utilized WinCSD software package. Visualization of the crystal structure, stacking and coordination polyhedra was performed using the VESTA program.
 The crystal structure of the selenides La3Pb0.1Ga1.6Sе7 and Pr3Pb0.1Ga1.6Sе7 was studied by the X-ray powder diffraction method and its belonging to the hexagonal crystal system was established (space group P63). The refinement of atom coordinates and isotropic temperature displacement parameters in this model yielded satisfactory values of fit factors. Analysis of hkl reflex indices and their intensity indicates that the structural of La(Pr)3Pb0.1Ga1.6Sе7 compounds belong to the structural type La3CuSiS7 (space group P63; a = 1.028 nm, c = 0.575 nm)
 Crystal structure of selenides La3Pb0.1Ga1.6Se7 (a = 1.05595(4) nm, c = 0.63868(3) nm, RI = 0.0983, Rp = 0.1672) and Pr3Pb0.1Ga1.6Se7 (a = 1.03727(6) nm, c = 0.63772(5) nm, RI = 0.0868, Rp = 0.2286) was studied by X-ray powder method. It was established that the structure of the synthesized selenides belongs to the structural type La3CuSiS7 (SG P63; PS hP24). In their structure, R = La(Pr) atoms are localized in site 6c and, together with selenium atoms, form trigonal prisms with one additional atom [R 1Se13Se23Se3]. Atoms of statistical mixtures M1 (0.64 Ga + 0.09 Pb) and M2 (0.58 Ga + 0.11 Pb), concentrated in site 2a, form octahedra [M1 6Se2] and [M2 6Se2]. These octahedra are interconnected by faces and form columns in the direction of the c axis. The Ga (site 2b) atoms are surrounded by four selenium atoms. The formed tetrahedra are oriented in the direction of the c axis and are isolated from each other. Gallium-containing selenides La3Pb0.1Ga1.6Sе7 and Pr3Pb0.1Ga1.6Sе7 based on lanthanum and praseodymium are promising chalcogenides based on which materials for nonlinear optics and thermoelectricity can be created.
 Keywords: rare-earth metals; chalcogenide; crystal structure; X-ray powder diffraction.

Enhancing Photovoltaic Performance of Ladder‐Type Heteroarene‐Based Electron Acceptors by Modulating Molecular Packing†

Comprehensive SummaryThe development of novel building blocks with sp3‐hybridized‐carbon‐free conjugated skeletons is important to further advance and enrich nonfullerene acceptors (NFAs), but this remains a challenge due to the lack of strategies to effectively modulate the aggregation behavior of resulting NFAs. Herein, two novel nitrogen‐bridged octacyclic ladder‐type heteroarenes end‐capped with thiophene rings (BTPS) or selenophene rings (BTPSe) are designed and synthesized as the donor cores for constructing NFAs (MQX‐2 and MQX‐4). It is found that replacing the sulfur atoms (MQX‐2) at the outer positions of the heteroarene core with selenium atoms (MQX‐4) can effectively modulate the molecular packing mode of the NFAs. The incorporation of selenium atoms induces stronger O···Se noncovalent interaction than O···S, thus promoting the formation of mixed H/J‐type aggregates in MQX‐4. Benefiting from more electron hopping channels, MQX‐4 exhibits higher electron transport (more than 1‐fold enhancement) and photovoltaic properties compared to MQX‐2, which forms only H‐type aggregates.

Spin transport properties of T-phase VSe2 2D materials based on eight-atom-ring line defects

Defects play a crucial role in modulating the properties of solid-state materials by inducing localized states that often benefit magnetic moments. Recently, direct experimental observations have shown the appearance of bunches of eight-atom-ring line defects in the T-phase VSe2 monolayer, a remarkable room-temperature two-dimensional magnetic metal. Using first-principles calculations, we have found that these line defects could enhance the magnetic moments, and half-metallicity (nearly 100% spin polarization) can be achieved in the structure with the densest defects. Furthermore, our analysis of the partial charge density distribution shows that a closer inter-defect distance between the d-states of vanadium atoms and p-states of selenium atoms increases the penalty of electrons occupying the spin-minority states. Moreover, we have discovered the high conductivity channel exhibits negative differential resistance characteristics within a bias range of 0.2 to 0.4 V (–0.4 to –0.2 V). Our findings broaden the scope of the applications of two-dimensional materials in spintronics and provide some theoretical guidance for the design of high-performance spintronic devices.

Effects of heavy bromine doping on the thermoelectric performance and dynamic stability of SnSe2 polycrystals

SnSe2 is a material with a layered crystal structure, which is abundant in the Earth's crust and is non-toxic. It exhibits anisotropic thermoelectric properties due to the anisotropy between its interlayer and intralayer electrical and thermal transport properties. However, its thermoelectric performance is intrinsically poor due to its lower electrical transport properties. In our study, we successfully synthesized n-type Bromine-doped SnSe2 polycrystals using a combined method of mechanical alloying (MA) and spark plasma sintering (SPS). Bromine (Br) acts as an electron donor, and its heavy doping has been achieved by substituting it with selenium (Se) atoms. This substitution results in a significant increase in carrier concentrations, thereby improving the thermoelectric performance of SnSe2. This Br doping has led to a notable improvement in the power factor, which increased to approximately 755 µWm−1K−2 at 573 K. The most significant anisotropy was observed in thermal conductivity, and Br doping led to an ultralow thermal conductivity of approximately 0.6 Wm−1K−1 at 748 K. Furthermore, density functional theory (DFT) was used to investigate the electronic structure and phonon dispersions. The results of our DFT calculations showed a shrinking bandgap and increased degeneracy, which supports the observed improvement in the thermoelectric performance of Bromine-doped SnSe2 polycrystals. Moreover, the absence of imaginary modes in the phonon dispersion confirmed the dynamical stability of the system after heavy Br doping. Finally, a maximum figure of merit (ZT) of 0.59 was obtained at 748 K for the SnSe1.95Br0.05 sample parallel to the SPS pressing direction, which is nearly sixfold higher than the value of pure SnSe2.

Multiple resonance thermally activated delayed fluorescence dendrimers containing selenium-doped polycyclic aromatic hydrocarbon emitters for solution-processed narrowband blue OLEDs

Three multiple resonance thermally activated delayed fluorescence dendrimers (BSeN-Cz, BSeN-DCz and BSeN-TCz) are developed by introducing the first-, second- and third-generation carbazole dendrons in periphery of selenium-doped polycyclic aromatic hydrocarbon emitter for solution-processed narrowband blue organic light-emitting diodes (OLEDs). It is found that the dendrimers show strong thermally activated delayed fluorescence effect with rapid reverse intersystem crossing rate constant of 8.5–9.1 × 106 s−1 owing to the strong heavy-atom effect and spin-orbit coupling of selenium atoms. Meanwhile, intermolecular aggregation is effectively suppressed in the dendrimers owing to steric hindrance effect of carbazole dendrons, leading to nearly invariable narrowband emissions with full width at half-maximum (FWHM) kept at 32 nm at doping concentration up to 100 wt% for BSeN-TCz bearing third-generation carbazole dendron. Solution-processed OLEDs based on multiple resonance dendrimer (BSeN-TCz) reveal blue electroluminescence at 478 nm with FWHM of 31 nm and Commission International de 1′Eclairage coordinates of (0.11, 0.21), together with maximum external quantum efficiency of 19.7%, which is promising device efficiency for narrowband blue electroluminescence by solution process.

Polarity switching via defect engineering in Cu doped SnSe0.75S0.25 solid solution for mid-temperature thermoelectric applications

Solid solution SnSe0.75S0.25 has potential to improve thermoelectric performance via ultra-low thermal conductivity as compared to the pristine SnSe which originates from phonon scattering due to disordered atoms of selenium (Se) and sulfur (S). SnSe0.75S0.25 and Cu-doped SnSe0.75S0.25 compounds were prepared via high energy ball milling and pelletized by a spark plasma sintering (SPS) process. Dislocation and point defects were successfully introduced by SnSe0.75S0.25. The existence of S in the Se site induced mass fluctuation which favors high-frequency phonon scattering. This leads to an impressively ultra-low thermal conductivity (κT) value of 0.258 W mK−1 at 753 K for SnSe0.75S0.25. Next, the Cu dopant was selected to enhance the electrical conductivity, which improved from 514.44 S m−1 (SnSe0.75S0.25) to 725.08 S m−1 for Sn0.98Cu0.02Se0.75S0.25 at 738 K. Interestingly, the Cu dopant induced nanoprecipitates of Cu2Se inside the grains, which further strengthens the phonon scattering. The Cu2Se nanoprecipitates and various defects at the grain boundaries contributed to a lower κT of 0.295 W mK−1 at 753 K for a Sn0.94Cu0.06Se0.75S0.25 sample. Moreover, the maximum figure of merit of (ZT) ∼0.19 at 738 K was attained for the Sn0.98Cu0.02Se0.75S0.25 sample.

New pecJ-n (n = 1, 2) Basis Sets for Selenium Atom Purposed for the Calculations of NMR Spin-Spin Coupling Constants Involving Selenium.

We present new compact pecJ-n (n = 1, 2) basis sets for the selenium atom developed for the quantum-chemical calculations of NMR spin-spin coupling constants (SSCCs) involving selenium nuclei. These basis sets were obtained at the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes (SOPPA(CCSD)) level with the property-energy consistent (PEC) method, which was introduced in our previous papers. The existing SSCC-oriented selenium basis sets are rather large in size, while the PEC method gives more compact basis sets that are capable of providing accuracy comparable to that reached using the property-oriented basis sets of larger sizes generated with a standard even-tempered technique. This is due to the fact that the PEC method is very different in its essence from the even-tempered approaches. It generates new exponents through the total optimization of angular spaces of trial basis sets with respect to the property under consideration and the total molecular energy. New basis sets were tested on the coupled cluster singles and doubles (CCSD) calculations of SSCCs involving selenium in the representative series of molecules, taking into account relativistic, solvent, and vibrational corrections. The comparison with the experiment showed that the accuracy of the results obtained with the pecJ-2 basis set is almost the same as that provided by a significantly larger basis set, aug-cc-pVTZ-J, while that achieved with a very compact pecJ-1 basis set is only slightly inferior to the accuracy provided by the former.

An Optochemical Oxygen Scavenger Enabling Spatiotemporal Control of Hypoxia.

We present an optochemical O2 scavenging system that enables precise spatiotemporal control of the level of hypoxia in living cells simply by adjusting the light intensity in the illuminated region. The system employs rhodamine containing a selenium or tellurium atom as an optochemical oxygen scavenger that rapidly consumes O2 by photochemical reaction with glutathione as a coreductant upon visible light irradiation (560-590 nm) and has a rapid response time, within a few minutes. The glutathione-consuming quantum yields of the system were calculated as about 5 %. The spatiotemporal O2 consuming in cultured cells was visualized with a hypoxia-responsive fluorescence probe, MAR. Phosphorescence lifetime imaging was applied to confirmed that different light intensities could generate different levels of hypoxia. To illustrate the potential utility of this system for hypoxia research, we show that it can spatiotemporally control calcium ion (Ca2+ ) influx into HEK293T cells expressing the hypoxia-responsive Ca2+ channel TRPA1.