Bond Lengths Research Articles

Synthesis and structure of trans-HfCl4(OEt2)2 and cis-ReCl4(OEt2)2, and computational studies of Group 4 to Group 7 MCl4(OEt2)2 isomer preferences (M = Zr, Hf, Nb, Ta, Mo, W, Re)

The bis(diethyl ether) adducts of early transition metal chlorides, MCl4(OEt2)2, serve as excellent precursors for complex inorganic and organometallic compounds due to the lability of the coordinated ethers. Previously reported MCl4(OEt2)2 (M = Zr, Nb, Ta, Mo, W) complexes have crystallized with the ethers in a trans conformation, even though computational studies have predicted that compounds of the type MX4L2 should form cis isomers. Herein, we report the crystal structure of trans-HfCl4(OEt2)2 and the synthesis and structure of cis-ReCl4(OEt2)2. The report of the crystal structure of the Hf analog completes the Groups 4–6 2nd and 3rd row series and provides structural context regarding the trans preference and observations in M-Cl and M-O bond distances that are corroborated by Shannon’s ionic radii of the M(IV) cations. The isolation of the cis-Re analog provides the first structural example of a Group 7 MCl4(OEt2)2 complex, as well as the first cis complex in the presented series. Computational studies were conducted to examine the cis/trans preferences across the entire series in the context of ionic radii, ligand hardness, and steric influence.

π-Conjugation as a Direct Estimate of Lewis Acidity.

A computational approach to directly estimate the relative acidity of a given Lewis acid is presented. This approach is based on the strength of the π-conjugation in trans-crotonaldehyde-Lewis acid complexes, the species used in the well-known Childs' Lewis acidity scale. It is found that the π-conjugative strength values given by the Energy Decomposition Analysis - Natural Orbital for Chemical Valence method strongly correlate not only with the variation of the bond lengths in the system, which are greatly affected by the nature of the Lewis acid, but also with the downfield shifts experienced by the different nuclei of the conjugated system upon binding to the Lewis acid. These strong correlations indicate that the (easy-to-compute) π-conjugation energies can be used as an alternative Lewis acidity scale.

A Multistep Oxidative Cascade Reaction from a Naphthalenediol-Based Pre-Ligand to a Tetranuclear Perylenequinone-Based FeIII Complex.

We have developed a family of dinuclear complexes using 2,7-disubstituted 1,8-naphthalenediol ligands that bind by molecular recognition to two neighboring phosphate diesters of the DNA backbone with the dinuclear CuII and NiII complexes exhibiting a severe cytotoxicity for human cancer cells. To increase the binding affinity, we intended to synthesize the corresponding dinuclear FeIII complex. Surprisingly, we obtained a tetranuclear FeIII perylene-based complex instead of the expected dinuclear FeIII naphthalene-based complex. In order to establish a rational and reproducible synthesis, we carefully analyzed this reaction. This revealed a multistep oxidative cascade reaction including the pre-coordination of FeII ions in the N3-binding pockets, the Lewis-acid assisted MOM-deprotection of the pre-ligand by the pre-oriented FeII ions, two oxidative aromatic C-C coupling reactions, oxidation of the perylene-based backbone and of FeII to FeIII. The careful analysis of bond lengths, HOMA indices (harmonic oscillation model of aromaticity), FTIR and UV-Vis-NIR spectra supported by DFT calculations reveals the presence of an aromatic 18-electron oxidized perylenequinone ligand backbone. In summary, a multistep cascade reaction involving in total a 10-electron oxidation has been established for the straight-forward synthesis of an unprecedented perylenequinone-based ligand system.

Enhancing trehalose production via Bacillus species G1 cyclodextrin glucanotransferase mutants: modifying disproportionation characteristics and thermal stability.

Inefficient conversion of small molecule maltooligosaccharides into trehalose greatly affects the cost of the production of trehalose by double enzyme method [maltooligosyl trehalose synthase (MTSase) and maltooligosyl trehalose trehalohyrolase (MTHase)]. This study used directed evolution to increase oligosaccharide utilization by the cyclomaltodextrin glucanotransferase (CGTase) from Bacillus species G1. This enzyme was chosen for its adaptability and stability in trehalose production. Model analysis revealed that the hydrogen bond distance between the N33K mutant and maltose reduced from 2.6 Å to 2.3 Å, increasing maltose affinity and boosting transglycosylation activity by 2.1-fold compared to the wild type. Further mutations improved thermal stability and optimum temperature, resulting in the N33K/S211G mutant. Consistent results from repeated experiments showed that the N33K/S211G mutant increased trehalose yield by 32.6% using maltodextrin. The results enhanced the double-enzyme method formed by MTSase and MTHase for trehalose production. Overall, we have identified optimal catalytic conditions, demonstrating significant potential for industrial-scale trehalose production with enhanced efficiency and cost-effectiveness.

Metal-halide perovskites under pressure: Effect of anisotropic deformation on optoelectronic properties

Significant differences from typical semiconductors are observed in organic lead halide perovskites, which arise from the hybrid nature and soft lattice that make them sensitive to external driving forces, such as temperature and pressure. Here, the study employs first-principles calculations to investigate the structural, electrical, optical, and mechanical properties of pressure-induced perovskite (FAPbI3). Cubic FAPbI3 (Pm3m) undergoes a series of phase transitions as pressure increases from 0 to 9 GPa: transitioning to a tetragonal phase at ∼2 GPa, an orthorhombic phase around 5 GPa, and eventually to a monoclinic phase near 8 GPa, accompanied by reductions in lattice constant, bond length, and octahedral angle. The anisotropic structural deformation adjusts the bandgap from 1.43 eV at 0 GPa to 1.10 eV at 5 GPa, resulting in a redshift, suggesting that photoelectric conversion efficiency could be enhanced under pressures less than 5 GPa. In addition, increased pressure enhances the ductility of FAPbI3, evident from the anisotropy ratio increasing from 1.2 at 0 GPa to 2.0 at 9 GPa. The significant tunability of FAPbI3 under modest pressure ranges, combined with its increased anisotropy and ductility, opens new paradigms for its optoelectronic applications in extreme environments.

DFT Study on the Interaction Between Flotation Agents and Lepidolite-1M Surfaces

The surface chemical properties of Lepidolite-1M crystals are closely related to their flotation properties. This paper uses density functional theory (DFT) to analyze the band structure, population, and state density of ideal Lepidolite-1M crystals. The results show that lepidolite-1M is an insulator, and its most probable positively charged active site is Al, and its negatively charged active sites are O and F. To further investigate the adsorption mechanism of Lepidolite-1M during comminution and flotation processes, we calculated the surface energy, population, state density, and differential charge density of its most common (001) surface. The results show that its surface energy is 0.9934 J/m2, occurred in the valence electron configurations, population values, and bond lengths of the surface atoms. Furthermore, oxygen atoms on the (001) surface showed different activities, with F and O atoms in the lithium-rich region showing significant electron enrichment. Overall, our results demonstrated that anion collectors react mainly with the Al sites on the surface of Lepidolite-1M, and the cationic collectors and metal ion activators can be adsorbed on the surface of Lepidolite-1M to produce better trapping and activation capabilities.

Connecting the liquid fragility to the average weakest metal–oxygen bond of its crystal in oxides

Glass and crystal are inherently different material states in terms of their structural and physical features; consequently, the direct quantitative connection between crystal and glass is lacking. Herein, we first show that the liquid fragility m, which is featured by the negative departure degree of viscosity with the temperature at the glass transition temperature (Tg), has a direct exponential correlation with the ratio of the average longest metal–oxygen and the average phosphorus, silicon, or boron–oxygen bond lengths of the crystal in various oxides including phosphates, silicates, and borates. Such a result can be rationalized by the fact that the fragility m in these glass-formers is associated with the total network rigidity determined by the weakest bond due to the “bucket effect” and the bond pair inheritance of glass from that of the crystal. Our work connects direct features between glass and crystal with identical composition, providing a new viewpoint bridging glass and crystal.

Identification of heterozygous mutations of ABCC8 gene responsible for maturity-onset diabetes of the young with exome sequencing

Abstract Background Although the MODY12 subtype, caused by ABCC8 mutations, is rare, it is highly sensitive to sulfonylureas. The identification of ABCC8 mutations in patients clinically diagnosed with MODY has the ability to contribute to the precise management of diabetes. Methods Genetic analysis of two families with MODY were conducted using whole-exome sequencing (WES) and Sanger sequencing. The spatial structures of the mutant proteins were constructed using MODELLER and PyMOL software to provide further evidence of pathogenicity. Results The heterozygous missense mutations V357I and R1393H in ABCC8 were found in probands of two unrelated MODY pedigrees, which co-segregated with the hyperglycemic phenotypes in these two pedigrees. Detection of the V357I mutation enabled the proband of family A to successfully transfer from insulin to sulfonylurea (SU). After 3 months of follow-up for the SU trial, the HbA1c level of proband A improved from 12.4% at the initial diagnosis to 7.20%. Proband B was treated with insulin because of pregnancy and poor islet function. In silico analysis indicated that the R1393H mutation resulted in a longer hydrogen bond distance to L1389 and cleavage of carbon-hydrogen bonds to V1395, A1390, and L1389. Conclusions We have described two pathogenic missense mutations in ABCC8 in Chinese families with MODY. Our findings support the heterogeneity in the clinical features of MODY12 caused by ABCC8 mutations.

The Trifluorooxygenate Anion [OF3]-: Spectroscopic Evidence for a Binary, Hypervalent Oxygen Species.

Experimental evidence for hypervalent compounds of second-row elements is still scarce in literature. Here, we present the first report of the long-sought binary, hypervalent trifluorooxygenate anion [OF3]-. It was isolated in solid Ne matrices under cryogenic conditions after reacting oxygen difluoride with free fluoride ions from laser ablation of alkali metal fluorides MF (M=Li-Cs). VSEPR theory and calculations at the CCSD(T) level predict a C2v-symmetric T-shape structure with one short and two long O-F bond lengths in [OF3]-. This is confirmed experimentally by FTIR spectroscopy in combination with isotopic labeling. Analysis of the natural local molecular orbitals shows the presence of one 2c-2e and one 3c-4e bond each. Natural resonance theory indicates the importance of the stability of [OF2]⋅- for the stability of [OF3]-. Although free [OF2]⋅- was not detected, the species MOF2 (M=Na-Cs) could be observed in the same experiments, which are best described as contact ion pairs of M+[OF2]⋅-.

Effect of Oriented External Electric Field in Altering Magnetic Exchange and Magnetic Anisotropy in Lanthanide-Radical Complexes.

Magnetic exchange coupling (J) is one of the important spin Hamiltonian parameters that control the magnetic characteristics of single-molecule magnets (SMMs). While numerous chemical methodologies have been proposed to modify ligands and control the J value, and magneto-structural correlations have been developed accordingly, altering this parameter through non-chemical means remains a challenging task. This study explores the impact of an Oriented-External Electric Field (OEEF) on over twenty lanthanide-radical complexes using Density Functional Theory (DFT) and ab initio Complete Active Space Self-Consistent Field (CASSCF) methods. Five complexes - [{(Me3Si)2N]2Gd(THF)}2(μ-η2:η2-N2)] (1), [Gd(Hbpz3)2(dtbsq)] (2), [Gd(hfac)3(IM-2py)] (3), [Gd(hfac)3(NITBzImH)] (4), and [Gd(hfac)3{2Py-NO}(H2O)] (5) - were selected for detailed analysis, revealing significant OEEF effects on magnetic exchange interactions and structural parameters. Various parameters such as bond distances, bond angles, and torsional angles were examined as a function of OEEF to establish guiding principles for molecule selection. In complexes 1, 2, and 3, OEEF influenced torsional angles and altered exchange interactions. Complex 4 demonstrated enhanced ferromagnetic coupling under OEEF, reaching a maximum J value of +5.3 cm-1. Complex 5 reveals switching the sign of JGd-rad exchange interaction from antiferromagnetic to ferromagnetic under OEEF, highlighting the potential of electric fields in designing materials with tuneable magnetic properties. These findings offer valuable insights for future research and applications in advanced materials and molecular electronics.

Das Trifluoroxygenat‐Anion [OF3]−: Spektroskopischer Nachweis einer Binären, Hypervalenten Sauerstoffspezies

AbstractExperimentelle Belege für hypervalente Verbindungen von Elementen der zweiten Periode sind in der Literatur selten. In dieser Arbeit berichten wir erstmals über das lange gesuchte binäre, hypervalente Trifluoroxygenat‐Anion [OF3]−. Es wurde gebildet durch die Reaktion von Sauerstoffdifluorid mit freien Fluorid‐Ionen, welche durch Laserablation von Alkalimetallfluoriden MF (M=Li−Cs) erzeugt wurden, und konnte unter kryogenen Bedingungen in Neonmatrizen isoliert werden. Das VSEPR‐Modell und Berechnungen auf CCSD(T)‐Niveau sagen eine C2v‐symmetrische T‐förmige Struktur mit einer kurzen und zwei langen O−F‐Bindungen für [OF3]− voraus. Dies wird durch FTIR‐Spektroskopie in Kombination mit Isotopenmarkierungs‐Experimente bestätigt. Eine Analyse der natürlichen lokalisierten Molekülorbitale zeigt das Vorliegen einer 2Z–2E‐Bindung und einer 3Z–4E‐Bindung an. Natural Resonance Theory weist auf die Bedeutung der Stabilität von [OF2]⋅− für die Stabilität von [OF3]− hin. Obwohl freies [OF2]⋅− nicht nachgewiesen wurde, konnten in denselben Experimenten die Spezies MOF2 (M=Na−Cs) beobachtet werden, die sich am besten als Kontaktionenpaar M+[OF2]⋅− beschreiben lassen.

Theoretical study of solvent effects on the white light emission mechanism of single molecule 4-OH-naphthalimide

Organic white light materials fabricated on the basis of single molecules have applied to manufacture the white light-emitting diodes due to their good photostability and relatively simple material preparation. In this work, the different fluorescence emission mechanisms of the NapH1 in n,n-dimethylformamide (DMF) and toluene are investigated to elucidate the process for generating single-molecule near-white-light. From the analysis of bond lengths and electrostatic potential analysis, the intermolecular hydrogen bond can form in DMF instead of in toluene. From the potential energy curves, it is clear that intermolecular proton transfer is not feasible in either DMF or toluene. Frontier molecular orbitals analysis, the dissociation constants and the vertical excitation energies are used to confirm that NapH1 can undergo the deprotonation process in DMF rather than in toluene. Combined with the calculations of the fluorescence values, only the original structure exists stably in toluene which emits blue fluorescence. And the dual fluorescence peaks of NapH1 in DMF are originated from the enol form and the deprotonated form, interacting jointly to emit near-white light. This work contributes to the investigation and advancement for single-molecule organic white luminescent materials.

Unexpected XPS Binding Energy Observations Further Highlighted by DFT Calculations of Ruthenocene-Containing [IrIII(ppy)2(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)2(FcCOCHCORc)

The series of iridium(III) complexes, [Ir(ppy)2(RCOCHCOR')], with R = CH3 and R' = CH3 (1), Rc (2), and Fc (3), as well as R = Rc and R' = Rc (4) or Fc (5), and R = R' = Fc (6), ppy = 2-phenylpyridinyl, Fc = FeII(η5-C5H4)(η5-C5H5), and Rc = RuII(η5-C5H4)(η5-C5H5), has been investigated by single-crystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ ΣχR ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing ΣχR (ΣχR = the sum of Gordy group electronegativities of the R groups on β-diketonato ligands = a measure of electron density on atoms), while in Fe 2p orbitals, XPS binding energy, as expected, increased with increasing ΣχR. Which trend direction prevails is a function of main quantum level, n = 1, 2, 3…, sub-quantum level (s, p, d, and f), initial state energies, and final state relaxation energies, and it may differ from compound series to compound series. Relations between DFT-calculated orbital energies and ΣχR followed opposite trend directions than binding energy/ΣχR trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f7/2 and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that 1 (IC50 = 25.1 μM) and 3 (IC50 = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC50 = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH2COCH3 (IC50 = 66.6 μM).

An Acceptor-Substituted N-Heterocyclic ortho-Quinodimethane: Pushing the Boundaries of Polarization in Donor-Acceptor-Substituted Polyenes.

We report the synthesis, isolation, and characterization of a stable donor-acceptor substituted ortho-quinodimethane (oQDM). This system with an imidazolidine scaffold as the donor can also be referred to as acceptor-substituted ortho-N-heterocyclic quinodimethane (oNHQ). We have examined the extent of polarization of the conjugated π-system using single-crystal X-ray diffraction, NMR and UV/vis spectroscopy, cyclic voltammetry, and DFT computations. The bond lengths in the phenyl linker do not exhibit the alternation typical of oQDMs. In addition, the 13C and 15N NMR shifts suggest significant charge separation, an interpretation supported by the diatropic ring current determined by NICSZZ(r) computations, which is characteristic of aromatic compounds. DFT calculations show that polarization is an electronic effect that is amplified by steric influences. More strikingly, the oxidation and reduction potentials of the push-pull substituted oQDM are virtually identical to those of authenticated anionic and cationic derivatives. The results therefore indicate that an aromatic zwitterionic structure represents the electronic structure more accurately than a neutral quinoidal Lewis structure, which indicates that the acceptor-substituted oNHQ is a rare example of an organic zwitterion in which the centers of charge are in conjugation. The ambiphilic reactivity of the acceptor-substituted oNHQ, which is evidenced by the dehydrogenation of ammonia borane and the addition of phenylacetylene via heterolytic C-H bond cleavage, further supports its notation as an organic zwitterion and is reminiscent of frustrated Lewis pairs (FLPs). Thus, the acceptor-substituted oNHQ can be considered to be an intramolecular carbogenic FLP in terms of its reactivity.

Relativistic Prolapse-Free Gaussian Basis Sets of Double- and Triple-ζ Quality for s- and p-Block Elements: (aug-)RPF-2Z and (aug-)RPF-3Z.

This study presents two new relativistic Gaussian basis sets without variational prolapse of double- and triple-ζ quality, RPF-2Z and RPF-3Z, along with augmented versions including additional diffuse functions, aug-RPF-2Z and aug-RPF-3Z, which are available for all s and p block elements from Hydrogen to Oganesson. The exponents of the Correlation/Polarization (C/P) functions are obtained from a polynomial version of the generator coordinate Dirac-Fock method (p-GCDF). The choice of C/P functions was guided by multireference configuration interaction calculations with single and double excitations (MR-CISD) based on a valence active space. Finally, calculations of fundamental properties done for atomic and molecular systems (bond lengths, vibrational frequencies, dipole moments, and electron affinities) ensure the expected quality of these new basis sets, which may also exhibit some computational efficiency advantages. Additionally, the prolapse-free feature of these sets must provide a reliable description of properties more dependent on core electron distributions, as well.

Modulating RuO2 Electrocatalysis via Introducing Lanthanides for Enhanced Acidic Oxygen Evolution

AbstractThe low activity of ruthenium dioxide (RuO2) and the rapid dissolution of the ruthenium (Ru) site during acid oxygen evolution reaction (OER) at high current density restricts its application in proton exchange membrane (PEM) electrolyzers. In this work, a series of rare‐earth (RE) elements doped RuO2 nanorods is developed as high‐performance OER electrocatalysts. X‐ray absorption spectroscopy suggests that RE doping regulates the local coordination environment around Ru sites, lowers the valance of Ru, and shortens the Ru─O─Ru(M) bond length, which enhances structural stability. Among the RE‐RuO2 samples, Sm‐RuO2 exhibits remarkable performance with a low overpotential of 283 mV to reach 100 mA cm−2 and maintained stability for over 140 h at 10 mA cm−2. Moreover, the PEM electrolyzer using Sm‐RuO2 as the anode can be stably operated at 500 mA cm−2 for 15 h. Electrochemical analysis, X‐ray photoelectron spectroscopy, and in situ Raman spectroscopy show that Sm doping lowers the d‐band center, reduces the adsorption energy of O intermediates to enhance the OER activity, and restrains excessive oxidation of Ru sites while stabilizing lattice oxygen during the OER process, thereby enhancing OER stability. This work offers valuable insights into improving the stability of metal oxide catalysts in acidic electrolytes.

Vacuum evaporation deposited RbxCs1-xPbBr3 thin films for spectrally tunable and stable all-inorganic blue light-emitting diodes

Perovskite light emitting diodes (PeLEDs) have emerged as a promising technology for new display applications due to their high color purity and precisely adjustable band gap. However, compared to green and red PeLEDs, blue PeLEDs suffer from lower luminous efficiency and stability. Traditionally, pure blue perovskite luminescence is achieved using mixed halogens, which often leads to phase separation issues. In this paper, we directly introduced RbBr and prepared RbxCs1-xPbBr3 (x = 0.5,0.6,0.7) thin films using thermal evaporation, achieving wavelength-tunable and stable blue light emission ranging from 477 nm to 489 nm.This is the first report of using thermal evaporation for the fabrication of RbxCs1-xPbBr3 films. PeLEDs based on these films exhibited stable electroluminescence under varying driving voltages. Operated continuously over 30 min at 6 V in ambient air with 36 % humidity, these devices showed superior spectral stability. Using pure bromine-based material RbxCs1-xPbBr3 (x = 0.5,0.6,0.7) in the light-emitting layer solves the problem of phase separation of mixed halogens and achieves blue-light emission. Additionally, the introduction of Rb+ distorts the crystal structure of perovskite. This distortion decreases the bond length of Pb-Br bonds, increases the bond energy, and raises the formation energy of halogen anion vacancies. As a result, the density of perovskite defect states decreases, and thus the stability is enhanced. This work represents a rare example of vacuum thermal-evaporation processed RbxCs1-xPbBr3 films and all-inorganic perovskite LEDs.

Investigating the adaptability of CsMF3 (M = Ge, Si) perovskites under hydrostatic pressure for improved optoelectronic performance: A DFT-based computational study

The Cesium-based halide perovskites CsMF3 (M = Ge, Si) were examined in detail, using density functional theory evaluated ab-initio calculations, under hydrostatic pressures varying between 0 and 40 GPa. The structural, electronic, bonding, optical, anisotropic elastic, and mechanical characteristics of prospective photovoltaic materials are examined to assess their viability. The structural, thermodynamical, mechanical, and vibrational stabilities are validated through the analysis of the Goldschmidt tolerance factor, formation energy, Born stability criteria, and phonon calculations, respectively. Both the GGA-PBE model and the non-local hybrid sX potential were utilized to estimate the structural parameters and electronic energy band gaps. The calculated band gaps indicate that the compounds exhibit semiconductor behavior at ambient pressure with values 2.074 eV (2.642 eV) for CsGeF3, and 1.097 eV (0.977 eV) for CsSiF3 utilizing GGA-PBE (hybrid sX) potential. However, increased pressure reduces the band gap, resulting in enhanced conductivity and causing a shift from a semiconductor to a metallic state. The charge density map distinguishes between the ionic character of the Cs-F bond and the covalent nature of the Ge/Si-F bond. When pressure is applied, the bond strength increases, leading to a uniform decrease in bond length. The application of pressure also improves the optical functionalities, suggesting that these materials could be effectively utilized in various optoelectronic devices designed for the visible and ultraviolet spectra. In addition, hydrostatic pressure has a significant influence on the mechanical characteristics while retaining stability. Under pressure, both the ductile and anisotropic characteristics become more prominent for CsMF3 (M = Ge, Si) solids.

Research on the bond performance between glass fiber reinforced polymer (GFRP) bars and Ultra-high performance concrete(UHPC)

In recent years, in order to overcome the problems that steel bars are prone to rust and the ductility of GFRP and ordinary concrete is insufficient, a new type of reinforced concrete structure with good durability and high ductility has been developed by combining glass fiber reinforced polymer (GFRP) bars with ultra-high performance concrete (UHPC). The bond performance between GFRP and UHPC is the guarantee for them to work together and achieve optimal performance, which is worthy of further research. In this paper, pull-out tests were performed on 75 center pull-out samples with a side length of 150 mm, taking into account factors such as GFRP bar diameter, surface treatment type, bond length, and fiber content. The failure modes and bond performance of GFRP bars and UHPC pull-out specimens were investigated. The results indicate that the bond-slip curves of GFRP bars in UHPC and ordinary concrete show similar bond-slip characteristics. Compared with ordinary concrete, UHPC pull-out specimens demonstrate superior mechanical properties, including better bond strength and ductility. The UHPC-GFRP bars and UHPC-steel bars (8 mm and 10 mm) underwent pull-out failure. However, the 12 mm steel bar in UHPC reached its ultimate tensile strength, causing pull-off failure. The bond strength of GFRP bars decreases with the increase of diameter. In addition, with the increase of bond anchorage length, the bond strength decreases. When GFRP bars of the same diameter are anchored in ultra-high-performance concrete, the GFRP bars with ribbed surfaces display superior bond performance compared to those with sandblasted surfaces. Based on the models proposed by previous researchers, this paper proposes a suitable formula for estimating the bond strength between GFRP bars and UHPC. The calculated results are in good agreement with the measured results.

Probing the Electronic Manifold of MgCl with Millimeter-Wave Spectroscopy and Theory: (3)2Σ+ and (4)2Σ+ States.

The millimeter/submillimeter spectrum of magnesium chloride (MgCl) has been observed in two new electronic excited states, (3)2Σ+ and (4)2Σ+, using direct absorption methods. The molecule was synthesized in a mixture of Cl2, argon, and magnesium vapor. For the (3)2Σ+ state, multiple rotational transitions were measured in the v = 0 level for all six isotopologues (24Mg35Cl, 24Mg37Cl, 25Mg35Cl, 25Mg37Cl, 26Mg35Cl, and 26Mg37Cl), as well as up to v = 13 for 24Mg35Cl. For the (4)2Σ+ state, less intense spectra were recorded for 24Mg35Cl (v = 0-2). Equilibrium rotational parameters were determined for both states for 24Mg35Cl, as well as rotational constants and 25Mg hyperfine parameters for the other isotopologues. A perturbation was observed between rotational levels of the two states due to an avoided crossing. Computations were also carried out at the CASPT2 and MRCISD+Q levels, and the resulting bond lengths for (3)2Σ+ and (4)2Σ+ states agree well with the experimental values of re = 2.536 and 2.361 Å. The computations show that the (3)2Σ+ state has a double-well potential; however, the state behaves as a single well with unperturbed vibrational levels up to v = 13 due to nonadiabatic interactions with the (4)2Σ+ state.