Unveiling the effect of 2D silagraphene structural diversity on electronic properties: DFT, DOS, and ELF studies.

Recently, fully π-functional two-dimensional (2D) materials have been reported for electronic device applications. Graphene is one of these 2D materials that is attributed to 2D electron confinement effects and exhibits an aromatic character; however, it is characterized by vanishing the bandgap energy. Hence, research was focused on the discovery of graphene-based 2D materials to reduce the bandgap energy. Herein, we investigate the silagraphene structures (SixCy) using DFT calculations to undertake and improve structural, physico-chemical, and electronic properties. Various types of 2D networks have been investigated by considering C-C and C-Si bonds in relative positions. Both conjugation and hyperconjugation phenomenon have been deeply examined and it seemed that they take advantage of each other depending on the C-C and C-Si bond positions. Localized orbital locator (LOL) and electron localization function (ELF) were also performed to examine the electronic densities in the investigated 2D networks and unveil the electronic properties of the studied materials.

Large gallanes and the PSEPT theory: a theoretical study of Ga(n)H(n+2) clusters (n = 7-9).

Do alanes Al(n)H(n+2) and gallanes Ga(n)H(n+2) satisfy the polyhedral skeletal electron pair theory (PSEPT)? Taking into account previous work on this question, this paper provides a convincing answer and proposes the reformulation of the (n + 1) electron pairs rule of Wade and Mingos (W-M) for such systems. Following recent studies of tetra-, penta-, hexa-, hepta-, octa-, and nonaalanes as well as valence-isoelectronic/related gallanes, in this paper we present an analysis of the hydrides of aluminum and gallium A(n)H(n+2) (A = Al, Ga and n = 7-9). The aim is still to examine the applicability of PSEPT, especially the W-M rule, to these clusters. Exploration of the total potential energy surfaces (PESs) of hepta-, octa-, and nonagallanes shows that the absolute minima have a nido-like polyhedron arrangement. Unlike the smaller Ga(n)H(n+2) (n = 4, 5, 6), it seems that the size of the cluster largely dictates its preferred geometry. Although none of them have closed (totally triangular) cages, these clusters exhibit significant compactness, comparable to borane double anions, B(n)H(n) (2-), which are the archetypes for the PSEPT theory.

Support vector machines: development of QSAR models for predicting anti-HIV-1 activity of TIBO derivatives.

The tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepinone (TIBO) derivatives, as non-nucleoside reverse transcriptase inhibitors, acquire a significant place in the treatment of the infections by the HIV. In the present paper, the support vector machines (SVM) are used to develop quantitative relationships between the anti-HIV activity and four molecular descriptors of 82 TIBO derivatives. The results obtained by SVM give good statistical results compared to those given by multiple linear regressions and artificial neural networks. The contribution of each descriptor to structure-activity relationships was evaluated. It indicates the importance of the hydrophobic parameter. The proposed method can be successfully used to predict the anti-HIV of TIBO derivatives with only four molecular descriptors which can be calculated directly from molecular structure alone.

The tri-mu-hydrido-bis[(eta(5)-C (5)Me (5))aluminum(III)] theoretical study, the assets of sandwiched M(2)H (3) (M of 13th group elements) stability.

The stability of the tri-mu-hydrido-bis[(eta(5)-C(5)Me(5))aluminum], Cp*(2)Al(2)H(3), 1 is studied at B3LYP/6-311+G(d,p), CCSD(T)//B3LYP/6-311+G(d,p) and MP4//B3LYP/6-311+G(d,p) levels. The coordination between Al(2)H(3) entity and both C(5)(CH(3))(5) groups is ensured by strong electrostatic and orbital interactions. The orbital analysis of the interacting fragments shows that Al(2)H(3) acceptor, which keeps its tribridged structure, implies the vacant [Formula: see text] and five antibonding ([Formula: see text], e' and e'') molecular orbitals to interact with two orbitals mixtures, b(1) and e" of the donors (C(5)Me(5)). When we take into account the solvent effect, the computation shows that 1 seems to be stable in condensed phase with a tribridged bond between the Al atoms [Cp*Al(micro-H)(3)AlCp*], whereas in the gas phase, the monobridged Cp*AlH(micro-H)AlHCp* 4 is slightly favored (4 kcal mol(-1)). We propose that 1 could be prepared thanks to Cp*Al (2) and Cp*AlH(2) (3) reaction in acidic medium. The experimental treatment of this type of metallocenes would contribute to the development of the organometallic chemistry of 13th group elements.

Hinge Distortion in Platinum(II) Dimers with a Pt(2)S(2) Ring. An ab Initio Molecular Orbital Study.

Ab initio calculations have been carried out for Pt(II) dimers with S(2)(-) and/or RS(-) bridging ligands in order to elucidate the factors governing the structural preference, planar or hinged, of these complexes. Calculations have been performed for systems which model all structurally characterized Pt(II) binuclear complexes. All possible determinants of the hinge angle have been taken into account in the ab initio calculations. These show that electronic rather than steric effects govern the geometry of the central Pt(2)S(2) ring. Only one minimum of energy has been found for each complex, but the energetic cost of the hinge motion is low. Complexes with two S(2)(-), or with one S(2)(-) and one RS(-), bridging ligands are hinged; the decrease of the through-ring antibonding interaction between the in-plane sulfur p orbitals with folding appears to be the determinant for hinging. Complexes with two RS(-) bridging ligands can be planar or hinged depending on the relative orientation, syn or anti, of the R groups, on the nature, L(4) or L(2)L(2)', of the terminal ligands, and in the latter case on their disposition, cis or trans. However, the aromatic or aliphatic nature of bridging thiolates does not influence the geometry of the Pt(2)S(2) ring significantly. Conclusions drawn from platinum dimers can be extended to the palladium analogs.