Enhancing CO reduction through the catalytic effect of a novel silicon haeckelite-inspired 2D material.

We propose a novel 2D material based on silicon haeckelite (Hck), whose structure contains a silicon atom arranged in a periodic pattern of pentagons and heptagons. Stacking the two layers gives rise to a planar geometry of the layers that compose it. This new structure presents a semiconductor character with a band gap of 0.

Catalytic activity of silicene biflakes for CO reduction: a theoretical approach.

The use of renewable energy sources to reduce carbon dioxide (CO) emissions has gained significant attention in recent years. The catalytic reduction of CO into value-added products is a promising approach to achieve this goal, and silicene biflakes (2Si) have been identified as potential candidates for this task. In this study, we explored the catalytic activity of these structures using density functional theory calculations.

Trifluoromethyl-stabilized 2D nitrogen clusters: a theoretical study.

The stability of 2D all nitrogen clusters containing from 6 to 96 nitrogen atoms, terminated with CF groups, has been explored using two computational models: dispersion corrected B3LYP functional and scaled opposite spin Møller-Plesset perturbation theory (SOS-MP2). Single point domain-based local pair natural orbital coupled-cluster theory calculations (DLPNO-CCSD(T)) was used for further energy refinement. All systems were found to be minima, and their stability increases with CF/N ratio.

Complexes of Li, Na, and Mg with 2D allotropies of second and third period: a theoretical study.

Complexes of Li, Na, and Mg with graphene, silicene, phosphorene nanoflakes (NFs), and their 2D allotropies have been studied at dispersion corrected TPSS/def-TZVP level of theory. The energy partition analysis of the complexes revealed that for most of the complexes exchange and correlation energies represent dominant contributions to the binding with strong charge transfer from the metal atom to a NF. The exceptions are Mg complexes of graphene and phosphorene NFs where binding is due to dispersion and correlation terms.

In silico modeling: electronic properties of phosphorene monoflakes and biflakes substituted with Al, Si, and S heteroatoms.

This contribution explores the systematic substitution of phosphorene monoflakes (Mfs) and biflakes (Bfs) with aluminum, silicon, and sulfur. These systems were investigated using density functional theory employing the TPSS exchange-correlation functional and complete active space self-consistent field (CASSCF) calculations. Al and Si substitution produces significant structural changes in both Mfs and Bfs compared to S-substituted and pristine systems.

Novel 2D allotropic forms and nanoflakes of silicon, phosphorus, and germanium: a computational study.

The structural variability offered by 2D materials is an essential feature in materials design. Despite its significance, obtaining assemblies with suitable stability remains a challenge. In this work, we theoretically explore novel silicon, phosphorus, and germanium, analogues of haeckelites at hybrid DFT level.

Halogen-Doping Effect on the Delithiation and Charge Transfer of (LiS) Cluster.

Previous studies have suggested beneficial effects in lithium-sulfur batteries containing iodide in a sulfur-based cathode or as an electrolyte additive. These effects include preventing electrolyte degradation and improving the cycle stability of Li-S cells. However, little is known regarding the underlying reasons of such performance improvements.

The electronic structure of van der Waals heterostructures formed by the nanoflakes of black phosphorene with those of graphene and haeckelites: their complexes with Li.

The electronic structure of the van der Waals heterostructures (HSs) of the phosphorene (P) nanoflakes (NFs) with graphene (G) and its allotropy (H1 and H2) NFs, and their complexes with Li have been studied using dispersion-corrected TPSS functional. According to the calculations, the attractive interactions in HSs come from dispersion. It has a relatively small contribution to the binding energy in Li complexes, especially for these forming complexes with G, H1, or H2 NF side.

Electronic structure of hybrid pentaheptite carbon nanoflakes containing boron-nitrogen motifs.

The electronic structure of isomeric graphene nanoflakes (NFs) heavily doped with boron and nitrogen atoms has been explored. Dispersion-corrected B3LYP functional has been used for the geometry optimizations. A complete active space method has been used for the energy evaluations.

Modeling of silicon- and aluminum-doped phosphorene nanoflakes.

The electronic structure of phosphorene nanoflakes (PNFs) doped with Al and Si has been explored using hybrid functional BHandHlyp/def2-SVP and complete active space (CASSCF) methods. Doping increases the bond length alternation and changes the overall PNF shape. Doping also decreases singlet-triplet splitting in the PNFs.

Detection of Multiconfigurational States of Hydrogen-Passivated Silicene Nanoclusters.

Utilizing density functional theory (DFT) and a complete active space self-consistent field (CASSCF) approach,we study the electronic properties of rectangular silicene nano clusters with hydrogen passivated edges denoted by H-SiNCs (n,n), with n and n representing the zigzag and armchair directions, respectively. The results show that in the n direction, the H-SiNCs prefer to be in a singlet (S = 0) ground state for n > n. However, a transition from a singlet (S = 0) to a triplet (S = 1) ground state is revealed for n > n.

DFT study of zinc, cadmium, mercury, copper, silver, and gold complexes of 21,23-dioxaporphyrin and one-dimensional arrays of those complexes.

Complexes of 21,23-dioxaporphyrin with neutral Zn, Cd, Hg, Cu, Ag, and Au atoms as well as some one-dimensional arrays of those complexes containing up to ten repeat units were modeled at the PBE/def2-TZVPP level of theory with D3 empirical dispersion correction. The binding energy between the metal atom and the macrocycle was found to vary from 90 kcal/mol for Cu to -14 kcal/mol for Hg. Strong charge transfer from the metal to the macrocycle accompanied complex formation.

Charge transfer complexes of fullerene[60] with porphyrins as molecular rectifiers. A theoretical study.

Molecular diodes based on charge transfer complexes of fullerene[60] with different metalloporphyrins have been modeled. Their current-voltage characteristics and the rectification ratios (RR) were calculated using direct ab initio method at PBE/def2-SVP level of theory with D3 dispersion correction, for voltages ranging from -2 to +2 V. The highest RR of 32.

Mechanistic aspects of superacid mediated condensation of polyphenols with ketones. Implications for polymer synthesis.

A detailed computational study of possible reaction paths for methanesulfonic and triflic acid mediated polyhydroxyalkylation reaction between resorcinol and trifluoracetone accompanied by cyclodehydration to give 9H-xanthene containing polymers has been carried out at M06-2X/6-311+G level of theory. A cluster solvation model was used for the calculations. The calculations revealed that the most kinetically favorable reaction path involves the cyclodehydration occurring during the polymer forming step.

Multiconfigurational character of the ground states of polycyclic aromatic hydrocarbons. A systematic study.

A systematic study of the electronic structure of polycyclic hydrocarbons from naphthalene to a system containing 80 fused benzene has been carried out. Geometries were optimized for closed shell singlet, open shell singlet, triplet and multiplet states at B3LYP/cc-pVDZ level of theory, D1 (second order Møller-Plesset) and D1 (second-order approximate coupled-cluster) diagnostics have been calculated for studied molecules. Complete active space self-consistent field (10,10)/6-31G(d) single point energy calculations have been carried out for all optimized structures.

Zinc-, cadmium-, and mercury-containing one-dimensional tetraphenylporphyrin arrays: a DFT study.

Metal-free, Zn-, Cd-, and Hg-containing one-dimensional tetraphenylporphyrin arrays containing up to eight repeat units were modeled at the PBE/def2-SVP level of theory with D3 empirical dispersion correction. Two different configurations--face to face (F) and parallel displaced (P)--were detected, the latter being the most stable for all types of nanoarrays. According to the calculations, the binding that occurs in nanoarrays is mostly due to dispersion, with binding energies of 33-35 kcal/mol seen for the metal-free nanoarrays and energies of 37-40 kcal/mol for the metal-containing ones.

Stabilization of gold nanowires inside nanoaggregates of cyclo[8]thiophene, cyclo[8]selenophene, and cyclo[8]tellurophene: a theoretical study.

The stabilities and electronic properties of gold clusters containing up to six atoms trapped inside cyclo[8]thiophene (CS8), cyclo[8]selenophene (CSe8), and cyclo[8]tellurophene (CTe8) nanoaggregates have been studied using the M06 functional. The 6-31G(d) basis set was used for all atoms except Au and Te, for which the LANL2DZ(d,p) pseudopotential basis set was applied. Single-point energy calculations were performed with the 6-311G(d,p) basis set for all atoms except for Au and Te, for which the cc-TZVP-pp pseudopotential basis set was used.

Two-photon excited fluorescence of silica nanoparticles loaded with a fluorene-based monomer and its cross-conjugated polymer: their application to cell imaging.

In this work the two-photon activity of nanoparticles obtained from a fluorene monomer (M1) and its cross-conjugated polymer (P1) is reported. Aqueous suspensions of M1 and P1 nanoparticles prepared through the reprecipitation method exhibited maximum two-photon absorption (TPA) cross-sections of 84 and 9860 GM (1 GM = 10(-50) cm(4) s) at 740 nm, respectively, and a fluorescence quantum yield of ~1. Such a two-photon activity was practically equal with respect to that for molecular solutions of M1 and P1.

Rectifying behavior of charge transfer complexes of tetrakis(dimethylamino)ethene with acceptor molecules: a theoretical study.

The effect of electric field induced electron transfer on the rectification properties of molecular rectifiers based on charge transfer complexes of tetrakis(dimethylamino)ethane (TDAE) with acceptor molecules was explored. The current-voltage curves and the rectification ratios (RR) for two different molecular rectifiers were obtained using a direct ab initio method at M06/LACVP(d) level of theory in the range from -2 to +2 V. The highest RR of 25.

"Russian doll" complexes of [n]cycloparaphenylenes: a theoretical study.

The formation of "Russian doll" complexes consisting of [n]cycloparaphenylenes was predicted using quantum chemistry tools. The electronic structures of multiple inclusion complexes containing up to four macrocycles were explored at the M06-2X/6-31G* level of theory. The binding energy between the macrocycles increases from the center to the periphery of the complex and can be >60 kcal mol(-1) for macrocycles containing 14 and 19 repeating units.

Complexes of C60 with cyclic oligothiophenes: a theoretical study.

Complexes of C60 and cyclic and linear oligothiophenes containing 8 and 12 repeating units have been modeled at the M05-2X/6-311G**//M05-2X/6-31G* level of theory. BSSE-corrected binding energies of neutral donor-acceptor complexes vary from 5 to 12 kcal/mol depending on the complex and donor type. Inclusion complexes formed by C60 and cyclooligothiophenes containing 8 repeating units were found to be the most stable ones.

Use of 4-piperidones in one-pot syntheses of novel, high-molecular-weight linear and virtually 100%-hyperbranched polymers.

4-Piperidone and 4-alkyl piperidones react selectively with aromatic hydrocarbons in a mixture of trifluoromethanesulfonic acid (TFSA) and CH(2)Cl(2) to give linear polymers, while N-(2-phenethyl)piperidone undergoes self-polymerization to yield virtually 100%-hyperbranched polymer.

Donor-acceptor tubular nanoaggregates of cyclic oligothiophenes. A theoretical study.

The geometries of neutral, monooxidized, and monoreduced donor-acceptor tubular aggregates of cyclo[8]thiophene, cyclo[8](3,4-dicyanothiophene), and the corresponding donor-acceptor tubular nanoaggregates containing up to 4 repeating units were fully optimized at MPWB1K/3-21G* level of theory. The binding energies between macrocycles in neutral donor-acceptor tubular aggregates (77-84 kcal/mol) were found to be much higher compared to donor (43-45 kcal/mol) or acceptor (27-28 kcal/mol) aggregates. The oxidation or the reduction of the donor-acceptor tubular aggregates lead to a decrement in the binding energy.

Construction of simplified models to simulate estrogenic disruptions by esters of 4-hydroxy benzoic acid (parabens).

Four parabens (methyl, n-butyl, benzyl and isobutylparaben) were theoretically studied in order to evaluate their estrogenic activity through simplified models. The experimental structure of the human estrogen receptor ligand-binding domain in complex with 17beta-estradiol was used as the starting point to construct the models. The complex between 17beta-estradiol and three fragments of the estrogenic receptor (Arg, Glu and His), resulted in a reasonable simplified model of interaction.