ABSTRACT
This study presents a collaborative experimental and theoretical investigation into the structures and electronic properties of niobium-doped germanium clusters. Anion photoelectron spectra for Nb1-2Gen- (n = 3-7) clusters were acquired using 266 nm photon energies, enabling the determination of adiabatic detachment energies and vertical detachment energies. In conjunction with these experimental measurements, density functional theory (DFT) calculations were conducted to validate the experimentally obtained electron detachment energies and elucidate the geometric and electronic structures of each anionic cluster. The agreement between DFT calculations and experimental data establishes a solid foundation for assessing the structural evolution and electronic properties of niobium-doped germanium clusters. It is noted that both neutral and anionic clusters exhibit predominantly similar overall structural characteristics, with the exception of Nb2Ge6- and Nb2Ge6. Furthermore, this investigation emphasizes the exceptional chemical stability of the D3d symmetric chair-shaped structure in Nb2Ge6-, providing insights into its bonding characteristics.
ABSTRACT
This study explores the structures and chemical bonding properties of TaSi17Ì and TaSi18Ì clusters by employing anion photoelectron spectroscopy and theoretical computations. Utilizing CALYPSO and ABCluster programs for initial structure prediction, B3LYP hybrid functional for optimization, and CCSD(T)/def2-TZVPPD level for energy calculations, the research identifies the most stable isomers of these clusters. Key findings include the identification of two coexisting low-energy isomers for TaSi17Ì , exhibiting Ta-endohedral fullerene-like cage structures, and the lowest-energy structures of TaSi17Ì and TaSi18Ì anions can be considered as derived from the TaSi16Ì superatom cluster. The study enhances the understanding of group 14 element chemistry and guides the design of novel inorganic metallic compounds, potentially impacting materials science.
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Silicon clusters infused with transition metals, notably gold, exhibit distinct characteristics crucial for advancing microelectronics, catalysts, and energy storage technologies. This investigation delves into the structural and bonding attributes of gold-infused silicon clusters, specifically AuSi2- and AuSi3-. Utilizing anion photoelectron spectroscopy and ab initio computations, we explored the most stable isomers of these clusters. The analysis incorporated Natural Population Analysis, electron localization function, molecular orbital diagrams, adaptive natural density partitioning, and Wiberg bond index for a comprehensive bond assessment. Our discoveries reveal that cyclic configurations with the Au atom atop the Si-Si linkage within the fundamental Si2 and Si3 clusters offer the most energetically favorable structures for AuSi2- and AuSi3- anions, alongside their neutral counterparts. These anions exhibit notable highest occupied molecular orbital-lowest unoccupied molecular orbital gaps and significant σ and π bonding patterns, contributing to their chemical stability. Furthermore, AuSi2- demonstrates π aromaticity, while AuSi3- showcases a distinctive blend of σ antiaromaticity and π aromaticity, crucial for their structural robustness. These revelations expand our comprehension of gold-infused silicon clusters, laying a theoretical groundwork for their potential applications in high-performance solar cells and advanced functional materials.
ABSTRACT
The structures and bonding characteristics of Ta2Si2Ì /0 clusters are investigated using anion photoelectron spectroscopy and quantum chemical calculations. The vertical detachment energy of the Ta2Si2Ì anion is measured to be 2.00 ± 0.08 eV using the 266 nm photon. It is found that the Ta2Si2Ì anion has three low-energy isomers with a C2v symmetric Ta-Ta dibridged structural framework, all of which contribute to the experimental photoelectron spectrum, while the Ta2Si2 neutral also has a C2v symmetric Ta-Ta dibridged structural framework. The charge-transfer from Ta atoms to Si atoms is discovered using atomic dipole moment corrected Hirshfeld analysis for the Ta2Si2Ì anion and Ta2Si2 neutral. Chemical bonding investigations show that both the Ta2Si2Ì anion and Ta2Si2 neutral have a strong covalent Ta-Ta bond, as well as σ and π double bonding patterns. Furthermore, the Ta atoms are linked together by a single 2c-2e Ta2 σ bond, whereas the Si atoms are linked together with the Ta atoms via four 2c-2e TaSi σ bonds, two 3c-2e TaSi2 σ bonds, one 4c-2e Ta2Si2 σ bond, and one 4c-2e Ta2Si2 π bond.
ABSTRACT
Using anion photoelectron spectroscopy and quantum chemical calculations, the structures and properties of OPt2-/0 are investigated. The vertical detachment energies (VDEs) of OPt2- are measured to be 3.28 eV and 3.23 eV through the use of 355 and 266 nm photons, respectively. The high experimental VDEs of OPt2- can be attributed to the strong Pt-Pt and Pt-O σ bonds and low orbital energy of the SOMO. It is found that neutral OPt2 has an OPt2 triangular structure with C2v symmetry and 1A1 electronic state. In the neutral OPt2, the O atom interacts with the Pt2 moiety by two 2c-2e PtO bonds, one 3c-2e Pt2O σ bond, and one 3c-2e Pt2O π bond. On the other hand, anionic OPt2 adopts a Pt-Pt-O bent structure with Cs symmetry and 2A' electronic state. NPA and ELF analyses indicate charge transfer upon complexation from the metal atoms to the O atom. Chemical bonding analyses show that OPt2-/0 have the strong covalent Pt-Pt and Pt-O bonds, and neutral OPt2 exhibits σ aromaticity and π antiaromaticity.
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A combined anion photoelectron spectroscopic and quantum chemical investigation was performed to explore the structures and bonding properties of ternary [O, Ta, 2C]- anions. The atomic bonding connectivity of the ternary anion was found to be (O-Ta-C2)- rather than (Ta-O-C2)-. The photoelectron spectrum using 266 nm photons was measured, and the theoretical simulated spectrum was calculated, with good agreement between experimental and theoretical results being found. Computations obtained electronic energies and low-energy structures and enabled chemical bonding analyses. The experimental vertical detachment energies of OTaC2- were measured to be 2.85 ± 0.08 eV. OTaC2- exhibits π aromaticity with two delocalized π electrons and σ antiaromaticity.
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Aim: Group A streptococcus (GAS) pharyngitis is a common clinical infection with significant morbidity but remains understudied. Materials & methods: We sought to assess the rates of testing and incidence of GAS pharyngitis in Calgary, Alberta based on age and sex. Results: A total of 1,074,154 tests were analyzed (58.8% female, mean age 24.8 years) of which 16.6% were positive. Age-standardized testing and positivity was greatest in the 5-14 years age group and lowest in persons over 75 years. Females had greater rates of testing and positivity throughout. Testing rates (incidence rate ratios: 1.40, 95% CI: 1.39-1.41) and case rates (incidence rate ratios: 1.36, 95% CI: 1.33-1.39) increased over time. Conclusion: Future studies should focus on evaluating disparities in testing and treatment outcomes to optimize the approach to this infection.
Subject(s)
Pharyngitis , Streptococcal Infections/epidemiology , Adolescent , Adult , Age Distribution , Aged , Canada/epidemiology , Child , Child, Preschool , Female , Humans , Incidence , Infant , Infant, Newborn , Male , Middle Aged , Pharyngitis/epidemiology , Sex Distribution , Young AdultABSTRACT
The structural evolution and electronic properties of TaSin-/0 (n = 2-15) clusters are explored using anion photoelectron spectroscopy accompanied by quantum chemical calculations. The Ta atom in TaSin-/0 is inclined to interact with more Si atoms and has high coordination numbers. The theoretical calculations show that TaSi2-/0 have trianglur structures and TaSi3-/0 adopt pyramid structures, while the geometries of TaSin-/0 (n = 4-7) are all exohedral structures dominated by bipyramid-based configurations with the Ta atom face-capping the Sin motifs. TaSi8-/0 and TaSi9-10- have boat-shaped geometries, whereas TaSi9-10 neutrals adopt bipyramid-based geometries instead of boat-shaped ones. TaSi11- and TaSi12 are confirmed as the critical size of transiting from exohedral to endohedral structures for anionic and neutral clusters, respectively. TaSi12-15-/0 have pentagonal or hexagonal prism-based geometries. Natural population analysis shows that the electron transfers from Sin skeletons to Ta atom. The second-order energy differences (Δ2E) and incremental binding energy (ΔEI) values exhibit strong odd-even alternations, suggesting that the TaSin-odd-/0 clusters are more stable than the adjacent TaSin-even-/0 ones, except that TaSi12-/0 are more stable than TaSi11-/0 and TaSi13-/0.
ABSTRACT
The structural evolution of medium-sized anionic and neutral Au2Sin (n = 8-20) clusters is investigated by using density functional theory (DFT) calculations and CCSD(T) methods in combination with the particle swarm optimization (CALYPSO) global search algorithm. The geometries of anionic and neutral Au2Sin clusters change from exohedral to endohedral ones with the increasing cluster sizes, and the critical size of forming Au2-endohedral structures for both anionic and neutral clusters is confirmed to be n = 20, in which a C2h symmetric Au2-endohedral cage-like structure is observed. Anionic and neutral Au2Sin clusters are primarily dominated by prism-based geometries with most of them adopting different structural features. It is found that the two Au atoms prefer to occupy low coordination sites and interact with fewer Si atoms. The Au atoms carry negative charges because of the electron-transfer from Sin frameworks. Meanwhile, the two Au atoms have very weak interactions. The second-order energy differences and incremental binding energies of anionic and neutral Au2Sin clusters exhibit an odd-even alternation and Au2Si20-/0 clusters are proven to have the highest chemical stability among these Au-Si clusters. Interestingly, Au2Si8-, Au2Si9-, Au2Si13-, Au2Si15-, and Au2Si17- anions, along with Au2Si13, Au2Si14, and Au2Si17 neutrals, have multiplicity of structural forms and their low-lying isomers show dynamical fluxionality due to the low barrier energies.
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We present a combined anion photoelectron spectroscopic and quantum chemical investigation on the structures and bonding properties of CPt2 -/0 and CPt2H-/0. The experimental vertical detachment energies of CPt2 - and CPt2H- are measured to be 1.91 ± 0.08 and 3.54 ± 0.08 eV, respectively. CPt2 - is identified as a C2v symmetric Pt-C-Pt bent structure, and CPt2 has a D∞h symmetric Pt-C-Pt linear structure. Both anionic and neutral CPt2H adopt a Pt-C-Pt-H chain-shaped structure, in which the â PtCPt and â CPtH bond angles of CPt2H- are larger than those of CPt2H. The Pt-C bonds in CPt2 -/0 and CPt2H-/0 exhibit covalent double bonding characters. The Pt=C bonds are much stronger than the C-H bond that may explain why the C atom CPt2H-/0 prefers to form Pt=C bonds rather than C-H bonds. It may also explain why platinum can insert into the C-H bond to activate the C-H bond as reported in the literature.
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The growth patterns of anionic and neutral B4Sin (n = 4-15) clusters are investigated by using density functional theory (DFT) calculations combined with particle swarm optimization (CALYPSO) software. The geometries of anionic and neutral B4Sin clusters transform from exohedral to endohedral structures with the increasing cluster sizes. The B4Si14- anion size is critical for forming B4-endohedral structures for anionic clusters, while the B4Si15 neutral size is the threshold size for forming B4-endohedral structures for neutral clusters. Both anionic and neutral B4Sin (n = 4-15) clusters are primarily dominated by prism-based or bipyramid-based geometries. The global minima of anionic and neutral B4Sin clusters adopt different geometrical structures, except for anionic and neutral B4Si10. The binding energies, second-order energy differences, and incremental binding energies of B4Sin- clusters show an odd-even alternation with the growing number of Si atoms. The B atoms in B4Sin-/0 exhibit B-B single bonding and B[double bond, length as m-dash]B double bonding properties. The B atoms are found to carry more negative charges due to charge transfer from Sin frameworks to B atoms. Interestingly, the B4Si4- anion adopts a C2h symmetric bicapped tetragonal bipyramid with σ plus π double bonding characters and has the highest relative stability among the anionic clusters. The bonding interactions in B4Si4- are in the order of B-B > B-Si > Si-Si.
ABSTRACT
The geometrical structures and electronic properties of anionic, neutral, and cationic B3Si11 clusters were investigated by performing ab initio calculations combined with size-selected anion photoelectron spectroscopy. The experimental photoelectron spectrum of the B3Si11- anion is reasonably reproduced by theoretical simulations of two competing isomers. The global minimum of the B3Si11- anion is formed by the fusion of a B3Si7 bicapped tetragonal antiprism to a B3Si4 pentagonal bipyramid by sharing a B3 triangle, while that of neutral B3Si11 has a B3-endohedral sandwich structure composed of a Si5 five-membered ring and a Si6 six-membered ring, and that of the B3Si11+ cation adopts a Si11 tricapped tetragonal antiprism with three face-capping B atoms. It is interesting that a Si5 five-membered ring and a Si6 six-membered ring are stabilized by three B atoms in B3Si11. The three B atoms tend to bond with each other to form a B3 triangle with stronger B-B bonds than B-Si bonds. Moreover, neutral B3Si11 exhibits σ + π double delocalized bonding patterns. Anionic, neutral, and cationic B3Si11 clusters have multiplicity of structural forms and their low-lying isomers show dynamical fluxionality. The bond lengths, bond orders, MO, constant electronic charge density surfaces, and PDOS analyses showed that the three B atoms in B3Si11 have strong bonding interactions.
ABSTRACT
OBJECTIVE: To investigate the effect and action mechanism of Yu Si Granules (YSG) in the treatment methyl methanesulphonate (MMS)-induced oligoasthenozoospermia (OAZ) in mice. METHODS: Thirty adult male mice were randomly divided into three groups of equal number, normal control, OAZ model control and YSG intervention. The OAZ model was established by oral administration of MMS and the model mice in the YSG intervention group were treated intragastrically with YSG suspension at 0.144 g/100 g of the body weight per day for 48 successive days. Then, all the mice were sacrificed and their epididymides harvested for detection of the sperm count and motility, observation of the morphology of the seminiferous tubules by HE staining, determination of the expressions of the germ cell-, sperm cell-, spermatocyte-, Sertoli cell- and blood-testis barrier-related genes by RT-PCR, and measurement of the levels of oxidative stress in the blood. RESULTS: Compared with the normal control, the OAZ model mice showed significantly decreased sperm count (ï¼»49.2 ± 0.7ï¼½ vs ï¼»23.6 ± 0.4ï¼½ ×107/ml/g, P < 0.05) and sperm motility (ï¼»76.3 ± 0.7ï¼½% vs ï¼»5.0 ± 5.8ï¼½%, P < 0.05), which were both remarkably increased after YSG intervention (ï¼»38.4 ± 0.5ï¼½ ×107/ml/g and ï¼»71.5 ± 0.5ï¼½%) (P < 0.05). The OAZ model mice also exhibited degenerated and atrophic seminiferous tubules, thinner seminiferous epithelia, disorderly arranged cells at different levels, reduced number of sperm in the lumen and unclear layers of germ cells in the epididymis, while those after YSG intervention manifested regularly organized seminiferous tubules with orderly arrangement and clear layers. The expressions of the Vasa, Dazl and Snd1 genes were significantly decreased (P < 0.05), but not those of Gfra, Plzf, Stra8, Spo11, Sycp3, Sox9 and Vim (P > 0.05) in the OAZ model and YSG intervention groups as compared with those in the normal control group. The superoxide dismutase (SOD) activity in the serum was markedly reduced in the OAZ model mice as compared with that in the normal controls (P < 0.05) and increased again after YSP intervention (P < 0.05), but the opposite was the case with the expression of the superoxide anion. CONCLUSIONS: YSG can significantly reduce MMS-induced OAZ in mice, which may be associated with oxidative stress.
Subject(s)
Asthenozoospermia/drug therapy , Drugs, Chinese Herbal/therapeutic use , Epididymis/drug effects , Testis/drug effects , Animals , Asthenozoospermia/chemically induced , Male , Methyl Methanesulfonate , Mice , Oxidative Stress , Random Allocation , Sperm Count , Sperm Motility , SpermatozoaABSTRACT
Size-selected anion photoelectron spectroscopy and theoretical calculations were used to investigate the structural evolution and bonding properties of BSin -/0 (n = 4-12) clusters. The results showed that the B atom in BSi4-12 -/0 prefers to occupy the high coordination sites to form more B-Si bonds. The lowest-lying isomers of BSi4-7 -/0 primarily adopt bowl-shaped based geometries, while those of BSi8-12 -/0 are mainly dominated by prismatic based geometries. For anionic clusters, BSi11 - is the critical size of the endohedral structure, whereas BSin neutrals form the B-endohedral structure at n = 9. Interestingly, both anionic and neutral BSi11 have a D 3h symmetric tricapped tetragonal antiprism structure with the B atom at the center and exhibit 3D aromaticity. The BSi11 - anion possesses σ plus π doubly delocalized bonding characters. The natural population analysis charge distributions on the B atom are related with the structural evolution of BSin - and the B-Si interactions.
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The photoelectron spectra of Au2Sin- (n = 1-7) clusters were measured, and the structural evolution and bonding properties of Au2Si1-7- anions and their corresponding neutral counterparts were investigated by theoretical calculations. The two Au atoms in Au2Si1-7-/0 prefer to occupy low coordinate sites and form fewer Au-Si bonds. The aurophilic interaction is fairly weak in these clusters. The most stable structures of both Au2Sin- anions and Au2Sin neutrals can be described as the two Au atoms interacting with the Sin frameworks. The most stable isomers of Au2Sin- anions are in spin doublet states, while those of the neutral clusters are in spin singlet states. The lowest-lying isomers of Au2Si1-/0 have C2v symmetric V-shaped structures. The global minimum of the Au2Si2- anion has a D2h symmetric planar rhombus structure, while that of the Au2Si2 neutral adopts a C2v symmetric dibridged structure. In Au2Si3-/0, the two Au atoms independently interact with the different Si-Si bonds of the Si3 triangular structure. The global minima of Au2Si4-7-/0 primarily adopt prismatic based geometries. Interestingly, Au2Si6-/0 have significant 3D aromaticity and possess σ plus π double bonding characters, which play important roles in their structural stability.
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The structural, electronic and magnetic properties of dual Cr atoms doped germanium anionic clusters, [Formula: see text] (n = 3-14), have been investigated by using photoelectron spectroscopy in combination with density-functional theory calculations. The low-lying structures of [Formula: see text] are determined by DFT based genetic algorithm optimization. For [Formula: see text] with n ⩽ 8, the structures are bipyramid-based geometries, while [Formula: see text] cluster has an opening cage-like structure, and the half-encapsulated structure is gradually covered by the additional Ge atoms to form closed-cage configuration with one Cr atom interior for n = 10 to 14. Meanwhile, the two Cr atoms in [Formula: see text] clusters tend to form a Cr-Cr bond rather than be separated. Interestingly, the magnetic moment of all the anionic clusters considered is 1 µ B. Almost all clusters exhibit antiferromagnetic Cr-Cr coupling, except for two clusters, [Formula: see text] and [Formula: see text]. To our knowledge, the [Formula: see text] cluster is the first kind of transition-metal doped semiconductor clusters that exhibit relatively stable antiferromagnetism within a wide size range. The experimental/theoretical results suggest high potential to modify the magnetic behavior of semiconductor clusters through introducing different transition-metal dopant atoms.
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We measured the photoelectron spectra of diatomic AuSi- and AuGe- and conducted calculations on the structures and electronic properties of AuSi-/0 and AuGe-/0. The calculations at the CASSCF/CASPT2 level confirmed that experimentally observed spectra features of AuSi- and AuGe- can be attributed to the transitions from the 3Σ- anionic ground state to the 2Π (2Π1/2 and 2Π3/2), 4Σ-, 32Σ+, and 42Σ+ electronic states of their neutral counterparts. The electron affinities (EAs) of AuSi and AuGe are determined by the experiments to be 1.54 ± 0.05 and 1.51 ± 0.05 eV, respectively. The spin-orbit splittings (2Π1/2-2Π3/2) of AuSi and AuGe measured in this work are in agreement with the literature values. The energy difference between the 4Σ- (A) and 2Π1/2 states of AuSi obtained in this work is in reasonable agreement with the literature value, while that of AuGe obtained in this work by anion photoelectron spectroscopy is slightly larger than the literature value by neutral emission spectroscopy. The term energies of the 32Σ+ (B) and 42Σ+ (C) states of AuSi and AuGe were also determined based on the photoelectron spectra. Because of the different bond lengths between the anionic and neutral states, the electronic state terms energies of AuSi and AuGe estimated from the anion photoelectron spectra might be slightly different from those obtained from the neutral emission spectra.
ABSTRACT
The anionic silicon clusters doped with three boron atoms, B3Sin- (n = 4-10), have been generated by laser vaporization and investigated by anion photoelectron spectroscopy. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) of these anionic clusters are determined. The lowest energy structures of B3Sin- (n = 4-10) clusters are globally searched using genetic algorithm incorporated with density functional theory (DFT) calculations. The photoelectron spectra, VDEs, ADEs of these B3Sin- clusters (n = 4-10) are simulated using B3LYP/6-311+G(d) calculations. Satisfactory agreement is found between theory and experiment. Most of the lowest-energy structures of B3Sin- (n = 4-10) clusters can be derived by using the squashed pentagonal bipyramid structure of B3Si4- as the major building unit. Analyses of natural charge populations show that the boron atoms always possess negative charges, and that the electrons transfer from the 3s orbital of silicon and the 2s orbital of boron to the 2p orbital of boron. The calculated average binding energies, second-order differences of energies, and the HOMO-LUMO gaps show that B3Si6- and B3Si9- clusters have relatively high stability and enhanced chemical inertness. In particular, the B3Si9- cluster with high symmetry (C3v) stands out as an interesting superatom cluster with a magic number of 40 skeletal electrons and a closed-shell electronic configuration of 1S21P61D102S22P61F14 for superatom orbitals.
ABSTRACT
Niobium-doped silicon clusters, NbSin- (n = 3-12), were generated by laser vaporization and investigated by anion photoelectron spectroscopy. The structures and electronic properties of NbSin- anions and their neutral counterparts were investigated with ab initio calculations and compared with the experimental results. It is found that the Nb atom in NbSin-/0 prefers to occupy the high coordination sites to form more Nb-Si bonds. The most stable structures of NbSi3-7-/0 are all exohedral structures with the Nb atom face-capping the Sin frameworks. At n = 8, both the anion and neutral adopt a boat-shaped structure and the openings of the boat-shaped structures remain unclosed in NbSi9-10-/0 clusters. The most stable structure of the NbSi11- anion is endohedral, while that of neutral NbSi11 is exohedral. The global minima of both the NbSi12- anion and neutral NbSi12 are D6h symmetric hexagonal prisms with the Nb atom at the center. The perfect D6h symmetric hexagonal prism of NbSi12- is electronically stable as it obeys the 18-electron rule and has a shell-closed electronic structure with a large HOMO-LUMO gap of 2.70 eV. The molecular orbital analysis of NbSi12- suggests that the delocalized Nb-Si12 ligand interactions may contribute to the stability of the D6h symmetric hexagonal prism. The AdNDP analysis shows that the delocalized 2c-2e Si-Si bonds and multicenter-2e NbSin bonds are important for the structural stability of the NbSi12- anion.
ABSTRACT
Gold-doped germanium clusters, AuGen(-) (n = 2-12), were investigated by using anion photoelectron spectroscopy in combination with ab initio calculations. Their geometric structures were determined by comparison of the theoretical calculations with the experimental results. The results show that the most stable isomers of AuGen(-) with n = 2-10 are all exohedral structures with the Au atom capping the vertex, edge or face of Gen clusters, while AuGe11(-) is found to be the critical size of the endohedral structure. Interestingly, AuGe12(-) has an Ih symmetric icosahedral structure with the Au atom located at the center. The molecular orbital analysis of the AuGe12(-) cluster suggests that the interactions between the 5d orbitals of the Au atom and the 4s4p hybridized orbitals of the Ge atoms may stabilize the Ih symmetric icosahedral cage and promote the Au atom to be encapsulated in the cage of Ge12. The NICS(0) and NICS(1) values are calculated to be -143.7 ppm and -36.3 ppm, respectively, indicating that the icosahedral AuGe12(-) cluster is significantly aromatic.
