Heterotridentate organodiphosphines in Pt(η3-P1X1P2)(Y) (X1 = B, S, or Si) and Pt(η3-P1P2Si1)(Y) derivatives-structural aspects

This review covers almost 30 Pt(II) complexes of the composition Pt(η3-P1X1P2)(Y), (X1 = BL, SL, or SiL), (Y = H, OL, NL, CL, Cl, PL, or I) and Pt(η3-P1P2Si1)(CH3). Heterotridentate ligands form six types of metallocyclic rings: P1CNB1NCP2, P1C2S1C2P2, P1C2Si1C2P2, (most common), P1CNSi1NCP2, and P1C3Si1C3P2 with common B1, S1, or Si1 atoms. In P1C2P2C3Si1 the P2 atom is common. The structural data (Pt–L, L–Pt–L) are analyzed and discussed with an attention to the distortion of a square-planar geometry about Pt(II) atoms as well as trans-influence. The sum of Pt–L(x4) bond distances growing with covalent radius of the X1 and Y atoms.

On the evaluation of hydrogen evolution reaction performance of metal-nitrogen-doped carbon electrocatalysts using machine learning technique

Single-atom catalysts (SACs) introduce as a promising category of electrocatalysts, especially in the water-splitting process. Recent studies have exhibited that nitrogen-doped carbon-based SACs can act as a great HER electrocatalyst. In this regard, Adaptive Neuro-Fuzzy Inference optimized by Gray Wolf Optimization (GWO) method was used to predict hydrogen adsorption energy (ΔG) obtained from density functional theory (DFT) for single transition-metal atoms including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, and Au embedded in N-doped carbon of different sizes. Various descriptors such as the covalent radius, Zunger radius of the atomic d-orbital, the formation energy of the single-atom site, ionization energy, electronegativity, the d-band center from − 6 to 6 eV, number of valence electrons, Bader charge, number of occupied d states from 0 to − 2 eV, and number of unoccupied d states from 0 to 2 eV were chosen as input parameters based on sensitivity analysis. The R-squared and MSE of the developed model were 0.967 and 0.029, respectively, confirming its great accuracy in determining hydrogen adsorption energy of metal/NC electrocatalysts.

Photocatalyzed cycloaromatization of vinylsilanes with arylsulfonylazides

Sila-molecules have recently attracted attention due to their promising applications in medical and industrial fields. Compared with all-carbon parent compounds, the different covalent radius and electronegativity of silicon from carbon generally endow the corresponding sila-analogs with unique biological activity and physicochemical properties. Vinylsilanes feature both silyl-hyperconjugation effect and versatile reactivities, developing vinylsilane-based Smiles rearrangement will therefore provide an efficient platform to assemble complex silacycles. Here we report a practical Ir(III)-catalyzed cycloaromatization of ortho-alkynylaryl vinylsilanes with arylsulfonyl azides for delivering naphthyl-fused benzosiloles under visible-light photoredox conditions. The combination of experiments and density functional theory (DFT) energy profiles reveals the reaction mechanism involving α-silyl radical Smiles rearrangement.

Анализ водородоустойчивости алюминиевых сплавов

It was established by the methods of quantum chemistry that tungsten W and rhenium Re are the most effective additives that increase the hydrogen resistance of aluminum Al. It is shown that W and Re strongly compress aluminum, but at the same time have a rather large covalent radius. In addition, each W and Re atom form stable chemical bonds with 12 Al atoms. As a result, the W and Re atoms strongly bind Al atoms significantly increasing the energy of vacancy formation and slowing down the process of hydrogen embrittlement. All basic physical and mechanical properties of the most hydrogen-resistant aluminum compound WReAl24 have been calculated using density functional theory.

Mechanisms of Carbon Nanotubes and Graphene Growth: Kinetics versus Thermodynamics

Thermodynamics must be favorable for the growth of carbon nanotubes (CNTs) and graphene to take place, but a kinetic study is required to find the operating mechanism. In fact, thermodynamics indicates whether a reaction is possible; however, the route prevailing is not necessarily the most thermodynamically favorable, but the fastest one. Detailed kinetic studies state that there are three alternative routes operating under different temperature and pressure rates. The modes and rates of diffusion of carbon (C) atoms and noble metals have been known since the 1930s, but proof of C bulk diffusion operating in CNT growth came from detailed kinetic studies performed in the early 1970s, when reversible versus irreversible C formation was discussed with examples. The reason for interstitial C bulk diffusion in transition metals is evidenced based on the values of covalent radius. The reason for operating under steady-state conditions (linearity of the weight versus time) when searching for the operating mechanism is discussed herein. The steady-state C formation process operates sometimes with two different solid phases at each side of the catalyst particle (e.g., Ni and Ni3C), with thicknesses proportional to 1/D of the respective C bulk diffusivities when the carbon bulk diffusion step is the rate-determining one.

Distortion isomers of cis-PtP2X2 and cis-PtP2XY derivatives – structural aspects

In this review, the structural parameters of distortion isomers of cis-monomeric Pt(II) coordination complexes with inner coordination spheres: Pt(PL)2X2 (X = OL, NL, SL, Br, I); Pt(PL)2(η2-X2L) (X = O2L, N2L, S2L, OSL, NSL, NSeL); Pt(η2-P2L)X2 (X = Br, I); Pt(η2-P2L)(η2-X2L) (X = O2L, OSL, NSL); Pt(η2-P2L)(NL)(Cl) and Pt(PL)(η2-P,SiL)(H) are analyzed. None of the distortion isomers with cis-configuration has a trans-partner. The distortion isomers differ mostly by the degree of distortion in the Pt-L and L-Pt-L angles. Some of the isomers also differ by crystal packing. The total mean values of Pt-P (monodentate) and Pt-P (bidentate) bond distances are 2.279 Å and 2.244 Å, respectively. The mean value of Pt-P (monodentate) (trans to H¯) of 2.320 Å is the highest one because of higher trans-influence of H¯ over PP3. The total mean values of Pt-X (trans to P) elongate quite well with the covalent radius of the X in the sequence: 1.57 Å (X = H) < 2.062 Å (O2L) < 2.095 Å (OL) < 2.108 Å (NL) < 2.154 Å (N2L) < 2.329 Å (Cl) < 2.342 Å (S2L) < 2.347 Å (SL) < 2.480 Å (Br) < 2.616 Å (I).

Ab initio study of structural stability and electronic properties of GeV in diamond

A complete theory is the guide and explanation of the experiment. According to the first principle, the stable structure of Ge vacancy color center (GeV) is the double vacancy center structure by using the constructed GeV color center supercell. The covalent radius and bond angle of GeV are explored by analyzing the microstructures. The electronic structure of GeV color center is calculated, and the charge transfers of GeV color center are explained, thereby demonstrating the existence of stable bonds. The principle of the energy-level transition of the GeV color center in terms of light emission is described. The effect of each element and energy level orbital is illustrated by the density-of-states diagram.

Variable combinations of organophosphines in PtP3X derivatives: Structural aspects

This review covers over fifty Pt (II) complexes of the compositions PtP3X (X = H, OL, NL, BL, Cl, SL, Br, or I). These complexes crystallized in three crystal classes: monoclinic (23 examples) triclinic (17 examples) and orthorhombic (11 examples). The PtP3Cl is most common with 23 examples. There are variable combinations of organophosphines monodentate – P; bidentate- P,P; P,N; P,B; and tridentate – P,P,P; P,O,P; P,N,P; and P,S,P. The structural parameters (Pt–L, L–Pt–L) are analyzed and discussed with an attention to the distortion of a square-planar geometry about the Pt (II) atoms as well as of trans-influence. The sums of Pt–L (x4) bond distances growing with covalent radius of the X-atoms.

Covalent Radii and New Applications

Ionocovalency theory is defined “…everything exists in ionocovalency, the harmony of ionic energy with the covalent environment.” The authors have succeeded in thoroughly studying ionic energy part of the ionocovalent theory, and will now focus target on the covalent environment part of the theory. The essence of chemical reactions and chemical bonds is the overlap of atomic orbitals, the electron density or the ionocovalent potential. The covalent radius rc is the unique parameter that can be considered as an atomic property derived from molecules for data reduction and can be assigned to the atoms interacting in molecules. In the present study, A new application view of covalent radii of multidimensional world is revealed by the ionocovalency theory which can quantitatively describe the chemical phenomena and qualitatively correlates to the universal observations.

Regularized perturbative series for the ionization potential of atomic ions

We study N-electron atoms with nuclear charge Z. It is well known that, in the cationic (Z > N) large-Z region, the atom behaves as a weakly interacting system. The anionic (Z < N) regime, on the other hand, is characterized by an instability threshold at [Formula: see text], below which the atom spontaneously emits an electron. We construct a regularized perturbative series (RPS) for the ionization potential that is based on the behaviors for large Z and Z near Zc. The large-Z expansion coefficients are analytically computed from perturbation theory, whereas the slope of the energy curve at Z = N − 1 is computed from a kind of zero-range forces theory that uses as input the electron affinity and the covalent radius of the neutral atom with N − 1 electrons. Relativistic effects in the one-particle Hamiltonian are considered at the level of first-order perturbation theory. Our RPS formula is to be used to check the consistency of the ionization potential values for atomic ions contained in the NIST database.