Computational Study of Electron Delocalization in Hexaarylbenzenes

A number of hexaarylbenzene compounds were studied theoretically, in order to compare energy changes as a result of the toroidal delocalization effect that is characteristic of all these species. The energy was studied taking advantage of locally designed isodesmic reactions. Results indicate that the amount of aromaticity manifested by each substituent is a factor that should be considered when assessing the quantity of energy dissipated from each aromatic center. The influence of different substituents on electronic delocalization is also analyzed, as well as the role played by their frontier molecular orbitals

Computational Termochemistry Study of the C80 Isomers and Their Endo Lanthanum Complexes by Applying Homodesmotic and Isodesmic Reactions

C80 is a fullerene species which appears in different isomeric configurations. A general homodesmotic reaction previously designed to study the energy of fullerenes was implemented, in order to analyze the energy of this family of isomers. These results concur with some of the experimental data, but energy differences referring to all the configurations yield novel propositions about their particular behavior. The corresponding lanthanum complexes are also analyzed here and a new isodesmic reaction was designed for this particular case

Computational Termochemistry Study of the C80 Isomers and Their Endo Lanthanum Complexes by Applying Homodesmotic and Isodesmic Reactions

C80 is a fullerene species which appears in different isomeric configurations. A general homodesmotic reaction previously designed to study the energy of fullerenes was implemented, in order to analyze the energy of this family of isomers. These results concur with some of the experimental data, but energy differences referring to all the configurations yield novel propositions about their particular behavior. The corresponding lanthanum complexes are also analyzed here and a new isodesmic reaction was designed for this particular case

Which Is The Best Sandwich Compound? Hexaphenylbenzene Substituted By Sandwich Compounds Bearing Sc, Cr, and Fe

The electronic properties of nine different hexaarylbenzene molecules substituted by sandwich compounds have been studied by applying density functional theory. Different structures and the particular electron donor power of these systems have been considered in order to analyze their oxidant capacity, using bis­(ciclopentadienyl) scandium, ferrocene, and bis­(benzene)chromium as sandwich compounds. Both monometallic and bimetallic combinations are investigated. According to the ionization energies and electron affinities, compounds with Cr are nucleophiles and represent the best electron donors, whereas compounds with Sc are electrophiles and represent the best electron acceptors. The worse electron donor or acceptor is hexakis­(4-ferrocenyl phenyl) benzene. This is very significant, as it implies that the very well-known electronic properties of hexakis­(4-ferrocenyl phenyl) benzene can be improved by substituting with other metals, such as Sc and Cr. This suggests several possible applications for these compounds

Deposit and Characterization of Semiconductor Films Based on Maleiperinone and Polymeric Matrix of (Poly(3,4-Ethylenedioxythiophene) Polystyrene Sulfonate)

The development of small semiconductor molecules such as the maleiperinone, have gained importance due to their applications in optoelectronics. In this work semiconductor films composed by a polymer matrix of PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) and maleiperinone were manufactured. The films used in the studies were deposited by vacuum evaporation and spin-coating techniques. Atomic force microscopy (AFM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Infrared spectroscopy were used for the analysis of morphological and structural films. The fundamental and the onset of the direct and indirect band gaps were also obtained by UV-vis spectroscopy. The band-model theory and the Density-functional theory (DFT) calculations were applied to determine the optical parameters. The dipole moment is 3.33 Db, and the high polarity gives a signal of the heterogeneous charge distribution along the structure of maleiperinone. Simple devices were made from the films and their electrical behavior was subsequently evaluated. The presence of the polymer decreased the energy barrier between the film and the anode, favoring the transport of charges in the device. Graphene decreased the absorption and its ohmic behavior make it a candidate to be used as a transparent electrode in optoelectronic devices. Finally, the MoO3 provides a behavior similar to a dielectric

Deposit and Characterization of Semiconductor Films Based on Maleiperinone and Polymeric Matrix of (Poly(3,4-Ethylenedioxythiophene) Polystyrene Sulfonate)

The development of small semiconductor molecules such as the maleiperinone, have gained importance due to their applications in optoelectronics. In this work semiconductor films composed by a polymer matrix of PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) and maleiperinone were manufactured. The films used in the studies were deposited by vacuum evaporation and spin-coating techniques. Atomic force microscopy (AFM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Infrared spectroscopy were used for the analysis of morphological and structural films. The fundamental and the onset of the direct and indirect band gaps were also obtained by UV-vis spectroscopy. The band-model theory and the Density-functional theory (DFT) calculations were applied to determine the optical parameters. The dipole moment is 3.33 Db, and the high polarity gives a signal of the heterogeneous charge distribution along the structure of maleiperinone. Simple devices were made from the films and their electrical behavior was subsequently evaluated. The presence of the polymer decreased the energy barrier between the film and the anode, favoring the transport of charges in the device. Graphene decreased the absorption and its ohmic behavior make it a candidate to be used as a transparent electrode in optoelectronic devices. Finally, the MoO3 provides a behavior similar to a dielectric

Electrochemical Corrosion of Titanium and Titanium Alloys Anodized in H2SO4 and H3PO4 Solutions

Titanium and its alloys have superior electrochemical properties compared to other alloy systems due to the formation of a protective TiO2 film on metal surfaces. The ability to generate the protective oxide layer will depend upon the type of alloy to be used. The aim of this work was to characterize the electrochemical corrosion behavior of titanium Ti-CP2 and alloys Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-4V, and Ti Beta-C. Samples were anodized in 1 M H2SO4 and H3PO4 solutions with a current density of 0.025 A/cm2. Electrochemical tests on anodized alloys were carried out using a three-electrode cell and exposed in two electrolytes, i.e., 3.5 wt % NaCl and 3.5 wt % H2SO4 solutions at room temperature. Scanning electron microscopy (SEM) was used to observe the morphology of anodized surfaces. The electrochemical techniques used were cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN), based on the ASTM-G61 and G199 standards. Regarding EN, two methods of data analysis were used: the frequency domain (power spectral density, PSD) and time-frequency domain (discrete wavelet transform). For non-anodized alloys, the results by CCP and EN indicate icorr values of ×10−6 A/cm2. However, under anodizing conditions, the icorr values vary from ×10−7 to ×10−9 A/cm2. The PSD Ψ0 values are higher for non-anodized alloys, while in anodized conditions, the values range from −138/−122 dBi (A2·Hz−1)1/2 to −131/−180 dBi (A2·Hz−1)1/2. Furthermore, the results indicated that the alloys anodized in the H3PO4 bath showed an electrochemical behavior that can be associated with a more homogeneous passive layer when exposed to the 3.5 wt % NaCl electrolyte. Alloys containing more beta-phase stabilizers formed a less homogeneous anodized layer. These alloys are widely used in aeronautical applications; thus, it is essential that these alloys have excellent corrosion performance in chloride and acid rain environments