Crystal structures of 3/4-pyridyl-based thiosemicarbazones and related Cu and Ni coordination compounds

In this investigation, the crystal structures of the thio-ligands 3-formylpyridine 4-phenylthiosemicarbazone (C13H12N4S, 1) and 4-benzoylpyridine 4-ethylthiosemicarbazone (C15H16N4S, 2), and of two new coordination compounds, chlorido(3-formylpyridine 4-phenylthiosemicarbazone-κS)bis(triphenylphosphane-κP)copper(I) acetonitrile monosolvate, [CuCl(C13H12N4S)(C18H15P)2]·CH3CN, 3, and bis(3-formylpyridine 4-ethylthiosemicarbazonato-κ2 N 1,S)nickel(II), [Ni(C9H11N4S)2], 4, are reported. In complex 3, the thio-ligand coordinates in a neutral form to the Cu atom through its S-donor atom, and in complex 4, the anionic thio-ligand chelates to the Ni atom through N- and S-donor atoms. The geometry of complex 3 is distorted tetrahedral [bond angles 99.70 (5)–123.23 (5)°], with the P—Cu—P bond angle being the largest, while that of complex 4 is square planar, with trans-S—Ni—S and N—Ni—N bond angles of 180°.

Synthesis and crystal structure of (E)-2-benzyl-1,3-diphenylisothiouronium iodide

In the title molecular salt, C20H19N2S+·I−, prepared by the reaction of 1,3-diphenylthiourea and benzyl iodide, the C—S—C thioether bond angle is 101.66 (9)° and electrons are delocalized over the N+= C—N skeleton. The dihedral angle between the aromatic rings attached to the N atoms is 40.60 (9)°. In the crystal, N—H...I hydrogen bonds link the components into [100] chains.

Microstructure and phonon behavior in W/Si periodic multilayer structures

The crystallinity of the tungsten (W) phase was improved with an increase in the thickness of this layer in the periodic W/Si multilayer structure. Both the α- and β- W phases were grown simultaneously and the contribution of these phases has modified upon a change in the thickness of the W layers. For thinner W layers, the thermodynamically metastable β- W phase was dominated, and with an increase in thickness, this phase has suppressed, and the stable α- W phase became prominent. The crystallite size of these phases was almost linearly proportional to the thickness of the W layers in the multilayers. With the increase in thickness of Si layers in multilayers, Raman scattering showed a decrease in bond-angle deviation of Si-Si bonding in the amorphous Si phase. The study revealed, ordering of Si-Si bonding in the amorphous phase of Si with an increase in thickness of these layers in periodic W/Si multilayers.

Applying first principles to study the structural, electronic, and magnetic properties of Pr adsorbed ASiNRs

Applying first-principles calculations, the investigation of the geometrical and electronic properties of Pr adsorption armchair silicene nanoribbons structure has been established. The results show that the bandgap doped Pr has been changed, which is the case for chemical adsorption on the surface of ASiNRs; this material became metallic with the peak of valance band contact fermi level. Moreover, the survey to find the optimal height 1.82 Å of Pr and 2.24 Å bond length Si-Si, and Si-Si-Si bond angle 108005’, energy adsorption is -7.65 eV, buckling is 0.43 Å with structure stability close to the pristine case, has brought good results for actively creating newly applied materials for the spintronic and optoelectronics field in the future.

Effect of off-stoichiometry on the thermal conductivity of amorphous GeTe

The reversible phase change of Germanium Telluride (GeTe) is essential for developing advanced non-volatile devices. We investigate off-stoichiometric effect on the thermal and structural properties of amorphous Ge$_{1-\delta}$Te (0 $\le$ $\delta$ $\le$ 0.12) via molecular dynamics. The structural optimization due to off-stoichiometry was taken into account with an empirical potential. Our simulated thermal conductivity is in the range of experimental observations. With increasing $\delta$, the thermal conductivity tends to be slightly reduced. Analysis on the coordinate number and the bond angle distribution indicates that the off-stoichiometric Ge$_{1-\delta}$Te still retain its ability of rapid phase transition. These results are helpful in reliable device design and modeling.

Synthesis, hydrogen bond interactions and crystal structure elucidation of some stable 2H-imidazolium salts

Reaction of 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (1) with phthalimide, quinazolinedione, thiophenole and 4-pyridinethiole led to the formation of the hydrogen-bonded salts, imidazolium phthalimide (2), imidazolium quinazolinedione (3), imidazolium thiophenolate (4) and imidazolium 4-pyridinethiolate (5), respectively, in good yield. In crystals of 2, the anion is linked to the imidazolium cation by a C–H···O hydrogen bond, while in 3 and 5 C–H···N hydrogen bonds are observed. In 4, the imidazolium ion is linked to the anion by C–H···S hydrogen bonds. In compounds 2, 3 and 5, the interionic hydrogen bonds are close to linearity, while the interionic hydrogen bond angle in 4 is 148.5(9)°.

1,3,5-Trifluoro-2,4,6-triiodobenzene–piperazine (2/1)

The single-crystal structure of the title compound, C4H10N2·2C6F3I3, features a moderately strong halogen bond between one of the three crystallographically distinct iodine atoms and the nitrogen atom. The iodine–nitrogen distance is 2.820 (3) Å, corresponding to 80% of the sum of their van der Waals radii. The C—I...N halogen bond angle is 178.0 (1)°, consistent with the linear interaction of nitrogen via a σ-hole opposite the carbon–iodine covalent bond. The other two iodine atoms do not engage in halogen bonding. Some weak C—H...F and —H...I interactions are also observed. The complete piperazine molecule is generated by symmetry.

The Effect of Structural Phase Transitions on Electronic and Optical Properties of CsPbI3 Pure Inorganic Perovskites

Hybrid inorganic perovskites (HIPs) have been developed in recent years as new high-efficiency semiconductors with a wide range of uses in various optoelectronic applications such as solar cells and light-emitting diodes (LEDs). In this work, we used a first-principles theoretical study to investigate the effects of phase transition on the electronic and optical properties of CsPbI3 pure inorganic perovskites. The results showed that at temperatures over 300 °C, the structure of CsPbI3 exhibits a cube phase (pm3m) with no tilt of PbI6 octahedra (distortion index = 0 and bond angle variance = 0). As the temperature decreases (approximately to room temperature), the PbI6 octahedra is tilted, and the distortion index and bond angle variance increase. Around room temperature, the CsPbI3 structure enters an orthorhombic phase with two tilts PbI6 octahedra. It was found that changing the halogens in all structures reduces the volume of PbI6 octahedra. The tilted PbI6 octahedra causes the distribution of interactions to vary drastically, which leads to a change in band gap energy. This is the main reason for the red and blue shifts in the absorption spectrum of CsPbI3. In general, it can be said that the origin of all changes in the structural, electronic, and optical properties of HIPs is the changes in the volume, orientation, and distortion index of PbI6 octahedra.

Predicting scalar coupling constants by graph angle-attention neural network

Scalar coupling constant (SCC), directly measured by nuclear magnetic resonance (NMR) spectroscopy, is a key parameter for molecular structure analysis, and widely used to predict unknown molecular structure. Restricted by the high cost of NMR experiments, it is impossible to measure the SCC of unknown molecules on a large scale. Using density functional theory (DFT) to theoretically calculate the SCC of molecules is incredibly challenging, due to the cost of substantial computational time and space. Graph neural networks (GNN) of artificial intelligence (AI) have great potential in constructing molecul ar-like topology models, which endows them the ability to rapidly predict SCC through data-driven machine learning methods, and avoiding time-consuming quantum chemical calculations. With a priori knowledge of angles, we propose a graph angle-attention neural network (GAANN) model to predict SCC by means of some easily accessible related information. GAANN, with a multilayer message-passing network and a self-attention mechanism, can accurately simulate the molecular-like topological structure and predict molecular properties. Our simulations show that the prediction accuracy by GAANN, with the log(MAE) = −2.52, is close to that by DFT calculations. Different from conventional AI methods, GAANN combining the AI method with quantum chemistry theory (Karplus equation) has a strong physicochemical interpretability about angles. From an AI perspective, we find that bond angle has the highest correlation with the SCC among all angle features (dihedral angle, bond angle, geometric angles) about multiple coupling types in the small molecule datasets.