Structural Chemistry最新文献

This study explores the nonlinear optical (NLO) properties of hexamine (HMT) doped with transition metals scandium (Sc) and titanium (Ti), exhibiting enhanced NLO responses for advanced photonic devices. Employing ωB97XD functional for optimization and calculations, the study examines geometric parameters, electronic excitation, exciton binding energy (E_b), and vertical ionization energy (VIE) using DFT and TD-DFT. High VIE (3.25 to 4.52 eV) indicates enhanced stability in doped systems. The HOMO-LUMO gap decreases from 10.69 eV in pure HMT to 3.30 to 4.85 eV in the designed systems. These systems exhibit thermodynamic stability with binding energies 3.51 to 4.27 kcal/mol, and Ti-HMT-Ti being the most stable. A two-level approximation method is utilized to determine linear polarizability and nonlinear first and second hyperpolarizability (α_static, β_static, γ_static), which exhibits the highest γ_static (6546.63 au) value of Sc-HMT-Sc. Orbital transitions, charge distribution, electrophilicity, and nucleophilicity are examined using TDM, EDDM, and ESP, respectively. PDOS and TDOS provide insights into HOMO-LUMO gap reduction, NCI identifies the weak interactions and broadened and red-shifted UV absorption spectra, all are in the favour of NLO response of designed complexes. So, these materials show exceptional NLO properties and promising for optoelectronic applications.

In this study, we employ density functional theory to investigate KXH₃ (X = Ca, Sc, Ti, & Ni) hydride perovskites for H2 storage applications. Lattice parameters calculated using GGA-PBE are 4.482 Å, 4.154 Å, 3.974 Å, and 3.686 Å for KCaH₃, KScH₃, KTiH₃, and KNiH₃, respectively. Electronic structure analysis shows KScH₃, KTiH₃, and KNiH₃ are metallic, while KCaH₃ is a semiconductor. Strong bonding and long bond lengths indicate high hydrogen storage potential. The materials exhibit thermodynamic and mechanical stability, suggesting feasibility for experimental synthesis. Gravimetric analysis reveals promising hydrogen storage capacities: 3.646 wt% (KCaH₃), 3.452 wt% (KScH₃), 3.346 wt% (KTiH₃), and 3.005 wt% (KNiH₃). Calculated hydrogen desorption temperatures range from 442.40 K to 614.82 K, indicating suitability for practical hydrogen storage applications. These findings highlight the potential of KXH₃ (X = Ca, Sc, Ti, & Ni) perovskites as effective hydrogen storage materials.

To delve into the microscopic property of the cluster RhSi_n (n = 6–15), this study employs the CALYPSO structure prediction program and density functional theory. The paper conducts a comprehensive theoretical analysis of the clusters, examining parameters such as structures, relative stabilities, charge transfer, vertical electron affinity, vertical ionization potential, chemical potential, chemical hardness, and infrared and Raman spectra. The optimization process reveals that the rhodium doping has clearly changed the structures of silicon clusters. The ground state geometries favor Rh-linked framework beginning from n = 6, and they favor Rh-encapsulated Si cages when n approach 10. RhSi₁₃ cluster is more stable than its neighbors. The charges transfer within the clusters always transfer from silicon atom to rhodium atom, and there is spd hybridization in RhSi_n cluster. The analyzed chemical potential and chemical hardness pointed out the RhSi₁₃ cluster has the stronger hardness than other clusters. At last, the infrared and Raman spectrum properties for RhSi₁₃ cluster are analyzed.

Based on the template-assisted cyclocondensation procedure, two Schiff-base macrocyclic mononuclear lanthanide complexes (Pr-2_l and Nd-2_l) with the “lasso-type” architecture have been synthesized. According to X-ray structure analysis, the central ten-coordinate lanthanide ions (Pr³⁺ and Nd³⁺) in two complexes have distorted bicapped square antiprism geometry, and this geometry is completely encircled by two axial chelating nitrates on each side of the 23-membered macrocyclic plane and six donors in the macrocyclic skeleton. With the higher relatively inhibitory rates, the complex Pr-2_l can show significant antimicrobial activities against C. albicans and MRSA with lower MIC values (7.81 and 3.91 μg·mL⁻¹), while complex Nd-2_l exhibited good antimicrobial activities for S. aureus, C. albicans, and MRSA whose MIC values are 1.95, 7.81, and 3.91 μg·mL⁻¹. This current work is believed to provide another practical approach to further construct new antimicrobial materials by the use of Schiff-base and lanthanide antimicrobial fragments.

Using the B3LYP-D3 functional and the 6-311++G(d,p) basis set, the fluoride (F⁻), chloride (Cl⁻), bromide (Br⁻), cyanide (CN⁻), nitrate (NO₃⁻), and sulfate (SO₄²⁻) affinities of perfluorocubane (PFC) was theoretically investigated. This anion receptor interacts to the selected anions by LP → σ* interactions. It was discovered that the charge distribution in a small radius and net charge value in anion have a significant impact on the anion affinities of PFC structure. The natural bond orbital (NBO) analysis was used for identifying the detailed characteristics of anion… PFC interactions. The ∆H value of anion affinity of PFC for F⁻, Cl⁻, Br⁻, CN⁻, NO₃⁻, and SO₄²⁻ was calculated as − 139.36, − 63.53, − 50.30, − 66.64, − 46.21, and − 151.28 kJ mol⁻¹, respectively. The obtained results show that the anion affinity of PFC for SO₄²⁻ and F⁻ are among the strong organic anion receptors.

Two lanthanide coordination polymers (CP) of Nd(III) and Tb(III) with 2,4,6-pyridinetricarboxylate ligands were synthesized by reacting Nd(III) or Tb(III) chlorides with 2,4,6-pyridinetricarboxylic acid (H₃ptc) by hydrothermal method at 180 °C. Their chemical formulas were {[Nd(ptc)(H₂O)₂]·H₂O}_n (CP-1) and {[Tb(ptc)(H₂O)₃]·H₂O}_n (CP-2). Two compounds were characterized by IR spectra and element analyses. The crystal structures were determined by X-ray single crystal diffraction. CP-1 formed three-dimensional (3D) structure by the connections of coordination bonds between Nd(III) and ptc ligands and CP-2 formed two-dimensional (2D) layered structure. They could produce the characteristic f-f transition luminescence of Nd(III) or Tb(III) ion with the excitations of UV-rays. The lifetime for ⁵D₄ excited state of Tb(III) in CP-2 was 741 μs. And the absolute quantum yield of photoluminescence for CP-2 can reach 60% (λ_ex = 295 nm).

Herein, we synthesized novel 4-methyl coumarin-incorporated heterocyclic azo dyes, and structures were confirmed by analytical and spectroscopic approaches. Computational studies were performed using the DFT method with a B3LYP/ 6–31 G (d, p) basis set used to explore the molecular geometry, Mullikan atomic charges, global reactive descriptors, MEP, and RDG. Nonlinear optical (NLO) analysis revealed that the first-order hyperpolarizability of 1d was 18 times greater than that of urea. Natural bond orbital (NBO) analysis showed that all the compounds had greater stability due to internal charge transfer. Solvatochromic behavior was analyzed using UV–Vis spectroscopy, and the absorbance was observed in the range of 380–445 nm. The electrochemical behavior was determined by cyclic voltammetry, which exhibited two reduction peaks and was used to calculate the energy of the molecules (E_HOMO-E_LUMO). The antimicrobial activity was studied against different pathogens Viz., E. coli, S. aureus, and A. flavus, and the results showed that the compounds had good antimicrobial efficacy. “Furthermore, in silico molecular docking results revealed that compounds 1b and 1a have good binding site energies against the target enzymes DNA gyrase and O-methyltransferase, respectively”.

Four acridinium/acridine derivatives have been prepared by mechanochemical synthesis and their crystal structure, supramolecular framework, interaction energy calculation, thermal analysis, and photophysical properties are studied and presented in this manuscript. In the crystal structure, the one- and two-dimensional supramolecular framework is constructed via various strong and weak intermolecular interactions such as N‒H…Cl, O‒H…N, O‒H…Cl, C‒H…Cl, C‒H…O, C‒H…π, and π…π, respectively. The contribution of intermolecular interaction in the three-dimensional molecular packing is studied by the Hirshfeld surface analysis. The calculated total energy value of intermolecular interaction/contacts observed between the molecular pairs in the acridine compound is stronger than the energy value of intermolecular interaction/contacts of acridinium derivatives. The energy value of π…π contacts exhibited between the molecular pairs is significantly stronger than other weak interactions. The thermogravimetric analysis reveals that the acridinium derivatives degrade in three steps whereas the acridine compound undergoes a single-step degradation. Studies show that the acridinium derivatives exhibit a better photoluminescence quantum yield when compared to the acridine compound, and the acridine compound experiences a photoluminescence quenching due to charge transfer interactions.

The modified version of quasi-SMILES is studied. Unlike the previous ones, the new version allows building codes of experimental conditions in a user-friendly (easily interpreted) form. The quasi-SMILES can be a convenient basis for discussion between experimentalists and developers of models. The optimal descriptors for regression one-parameter models were calculated with the Monte Carlo method, using the vector of ideality of correlation. The vector of the ideality of correlation has two components: (i) the index of ideality of correlation (IIC) and (ii) the correlation intensity index (CII). Both the indices are components of the stochastic Monte Carlo process. The contribution of these indices is paradoxical: they improve the statistical quality of a model on the external validation set but to the detriment of the statistical quality of the model for the training set. Taking into account IIC and CII values for the Monte Carlo optimization gives an improvement of models of zeta potential of considered nanoparticles. The described approach is convenient for modelling the zeta potential of the considered nanoparticles. No less important is the universality of the use of quasi-SMILES as a means for studying the values of endpoints in the form of mathematical functions of not only the structures of the simulated objects (nanoparticles) but also the experimental conditions.