Simple Charge-Transfer Model for Metallic Complexes

Self-Assembled Monolayer of Monomercaptoundecahydro-closo-dodecaborate on a Polycrystalline Gold Surface

In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B₁₂H₁₁SH]²⁻ in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B₁₂H₁₁SH]²⁻ in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B₁₂H₁₁SH]²⁻, cyclic voltammetry response of the probe Fe(CN)₆³⁻/Fe(CN)₆⁴⁻ showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented R_tc and C_dl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B₁₂H₁₁SH]²⁻ diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B₁₂H₁₁SH]²⁻ and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode–solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B₁₂H₁₁SH]²⁻ were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer.

Predicted structure and selectivity of 3d transition metal complexes with glutamic N,N-bis(carboxymethyl) acid

Structure and selectivity of 3d transition metal complexes with glutamic N,N-bis(carboxymethyl) acid are analyzed and predicted from DFT calculations.

Theoretical characterization of first and second generation Grubbs catalysts in styrene cross-metathesis reactions: insights from conceptual DFT

Reorganization energy and DFT-based reactivity descriptors revealed important issues regarding the performance of Grubbs catalysts.

Ligand(s)-to-metal charge transfer as a factor controlling the equilibrium constants of late first-row transition metal complexes: revealing the Irving–Williams thermodynamical series

Ligand(s)-to-metal charge transfer obtained from QTAIM charges unravel the Irving–William series for the equilibrium constants of late first-row bivalent metal ions.

Keto, thione, selone, and tellone carotenoids — Changing antioxidants to antireductants

Heterocarotenoids can be considered as xenobiotic compounds as they are foreign to living organisms. Thione carotenoids are heterocarotenoids that are particularly interesting because the presence of sulfur shifted the absorption to longer wavelengths than the corresponding keto carotenoids. This may be important for further applications such as the development of new pigments. Keto carotenoids are well-known antiradical molecules, however, nothing is known about heterocarotenoids acting as free radical scavengers. Thus, the main goal of this investigation is to study the antiradical properties of some heterocarotenoids, such as thione, selone, and tellone carotenoids. For this purpose, the energy differences between singlets and triplets are used to analyze the singlet oxygen quenching mechanism, and the electron transfer mechanism is investigated, taking into account that these may constitute antiradical molecules either donating or accepting electrons (antioxidants or antireductants). To analyze these mechanisms, vertical ionization energy (I), vertical electron affinity (A), and electrodonating (χ−) and electroaccepting (χ+) electronegativities were evaluated by applying density functional theory calculations. The investigated heterocarotenoids are as effective as keto carotenoids in terms of being either electron donors or acceptors, and therefore, they have a similar capacity for scavenging free radicals. Changing the C=O group to C=S, C=Se, or C=Te converts an antioxidant to an antireductant.