Density functional investigation of the molecular geometries,harmonic vibrational frequencies,singlet-triplet energy separations,adiabatic ionization potentials,and electron affinities of XY2 (X = Si,Ge, Sn; Y = F,Cl) systems

The geometrical and spectroscopic parameters of SiF₂, SiCl₂, GeF₂, GeCl₂, SnF₂, and SnCl₂ were determined using the linear combination of Gaussian-type orbitals-local spin density (LCGTO-LSD) method and employing both the local (LSD) and nonlocal functionals (NLSD) for the exchange-correlation energy. A general good agreement with available experimental information and with previous high-level correlated computations was found. Data on cations and anions are reported for the first time and can be used, together with those on neutral systems, to stimulate future and desirable experimental work on this significant class of molecules. © 1997 John Wiley & Sons, Inc.     

Aurophilic attraction: the additivity and the combination with hydrogen bonds

The coexistence of gold–gold contacts and hydrogen bonding is studied in the model system [H₂P(OH)AuCl]₂ and [H₂P(OH)AuPH₂(O)]₂. The two interactions are found to be comparable. The possible non-additivity of the aurophilic, Au(I)–Au(I) interaction is studied at MP2 level for the pentagonal [Au(SH)₂(AuSH)₅)]⁻ and hexagonal [Au(SH)₂(AuSH)₆]⁻ clusters. The possibilities of ‘mechanical cooperativity’ between different aurophilic attractions and of Au…S attractions are also considered.     

Absorption spectra of first-row transition metal complexes of bacteriochlorins: a theoretical analysis

A theoretical study on a family of divalent transition metal bacteriochlorin complexes (M-BC, where M = Mn, Fe, Co, Ni Cu, and Zn) has been carried out to elucidate their potentialities as active molecules in photodynamic therapy (PDT). To draw a complete picture of their electronic properties, both for the ground and excited states, these complexes have been studied by the means of density functional theory (DFT). The time-dependent DFT (TDDFT) approach was used to interpret the electronic spectra, while solvent effects were taken into account by explicitly considering both two water molecules coordinated to the central metal atom and the contribution from the solvent bulk. Particular attention has been devoted to the analysis of the so-called Q bands, since these can be particularly important for medical applications. Metal substitution and environment (solvent) effects have been analyzed, and good agreement is found between computed and available UV-vis spectra. These theoretical data, especially those relative to the metallobacteriochlorins not yet completely characterized at the experimental level, could give some hints for future medical applications.     

Structural Surface Features of Paramagnetic Multifunctional Nanohybrids Based on Silver Oleic Acid

Sols of core–shell silver nanoparticles (AgNPs) are synthesized by electrochemical method. The method provides the ability to adjust the particle size by changing both the concentration of oleic acid and the residence time τ₀ in the organic phase. We synthesized AgNPs with oleic acid (OA) concentration of 0.25% (AgNPs & 0.25% OA) and 0.75% (AgNPs & 0.75% OA). These nanoparticles have been studied using modern physical–chemical methods. Differential thermal analysis curves indicate the chemical nature of bond ligand in the secondary shell; this conclusion is confirmed by quantum chemical simulation and semi-empirical calculation. In the electron paramagnetic resonance spectra of silver-containing sols AgNPs & 0.25% OA and AgNPs & 0.75% OA complex wide asymmetric signals of 500–800 G and g-factor of 2.09–2.13 are recorded, in addition, in the spectra of AgNPs with bilayer the pronounced ferromagnetic contribution is observed. The change of the oleic acid layers of the particles affects the dimension of the nanocrystallites that are being formed and the manifestation of their magnetism.

Trial registration number and date of registration JCS-P-20-03-0188.R1, 22-Sep-2020 (02-Mar-2020)

Graphic Abstract

     

Identification and assay of organophosphates in organic oranges by gas chromatography with pulsed flame photometric detection and ion-trap mass spectrometry

Multiresidue analysis for organophosphates in organic oranges grown in Calabria (Italy) is performed by the combined use of a pulsed flame photometric detector and an ion-trap mass spectrometer simultaneously coupled to a gas chromatograph through a double-hole ferrule. The method provides the retention times (RTs) of the phosphorus-containing analytes only. The extracted ion chromatograms at the previously determined RTs are used for full identification of the species through a mass spectra library search and for quantitative evaluation of each species in the natural matrix. The banned pesticide ronnel was used as an internal standard because of its chemical structure, which is perfectly suited to the performance of both detectors.     

Mechanistic aspects of the reaction of Th+ and Th2+ with water in the gas phase

Density functional theory calculations were performed to study the gas-phase reaction of Th(+) and Th(2+) with water. An in-depth analysis of the reaction pathways leading to different reaction products is presented. The obtained results are compared to experimental data and to the previously studied reactions of U cations with water.     

The Catalytic Mechanism of Protein Phosphatase 5 Established by DFT Calculations

In order to elucidate the catalytic mechanism of the Mn–Mn containing serine/threonine protein phosphatase 5 (PP5), we present a density functional theory study with a cluster model approach. According to our results, the reaction occurs through an in‐line concerted transition state with an energy of 15.8 kcal mol^?1, and no intermediates are formed. The important role played by His304 and Asp274 as stabilizers of the leaving group has been shown, whereas the role played by the metal ions seems to be mostly electrostatic. The indispensable requirement of having a neutral active center has been demonstrated by testing different protonation states of the cluster model. We have shown also the importance of describing properly the electronic configuration of the Mn–Mn binuclear centers.