Performance of exchange-correlation functionals on describing ground state geometries and excitations of Alizarin Red S : Effect of complexation and degree of deprotonation

Ground state optimizations and excited state calculations were performed to analyze the possible anionic forms of Alizarin Red S(ulphonated) and its ML2 type metal complexes formed with palladium(II). Six functionals have been tested (B3LYP, M06-2X, M06, BH&HLYP, PBE0, LC-wPBE, and CAM-B3LYP) with two basis sets (6-311+g(d,p) and TZVP). The relative errors of these functionals in reproducing the experimental UV-Vis absorption wavelengths are reported for the energetically lowest lying isomers. It was found that the degree of deprotonation affects several functionals in a systematic way. M06 and CAM-B3LYP xc-functionals gave the best estimates according to the average relative errors. These two functionals were then used to explore the coordination mode (hydroxy-keto or catechol) of the palladium(II) complexes and the effect of (de)protonation. © 2014 Elsevier B.V

The kinetics and mechanism of the oxidation of pyruvate ion by hypochlorous acid.

The oxidn. of pyruvic acid by hypochlorous acid was studied in the pH 1.0-11.0 range. The main path in the redox process is the reaction between the pyruvate ion and HOCl. It was shown that the reaction is second order in both reactants and kHOCl = 2.17 ± 0.04 M-1 s-1 (I = 1.0 M (NaClO4), T = 25.0 °C) with ΔH≠HOCl = 34.6 ± 1.2 kJ mol-1 and ΔS≠HOCl = -120.3 ± 3.6 J mol-1 K-1 for this reaction step. The relatively large neg. entropy of activation is consistent with an O atom-transfer mechanism. DFT calcns. support this conclusion by predicting a concerted rearrangement of the activated complex which includes the reactants and the solvent water mol. It was also confirmed that the hydration of pyruvic acid has a significant contribution to the obsd. kinetic features under acidic conditions. The hydration reaction is a proton catalyzed process and the pseudo-first-order rate const. can be interpreted by considering the protolytic and hydration equil. of pyruvic acid. The rate consts. were detd. for the non-catalytic and the proton catalyzed paths: kh0 = 0.24 ± 0.01 s-1 and kh1 = 5.5 ± 0.2 M-1 s-1. [on SciFinder(R)

Palládium-szalán komplexek flexibilitásának modellezése: Modeling the flexibility of palladium-salan complexes

A novel simple topological description of metal-salen-type complexes is presented through the palladium-(sulfo)salan model compound. The selected coordinates with which we define the spatial position of the spine and arms are suitable for systematic conformational analysis, which also makes it possible to find less favorable conformers by quantum chemical methods. Comparison of different compounds and isomers becomes easy using these coordinates.Palladium-salan complexes are also used in hydrogenation reactions, the catalytically active form of which, the monohydride complex, can be formed in several possible ways. In the first step of the process, the substitution of the phenolate arm and the hydrogen molecule takes place directly or via an aqua-complex intermediate, indirectly. Direct proton transfer from the coordinated hydrogen molecule to the oxygen of the phenolate arm is preferred, which in most cases is the rate-determining step. We also examined the emerging hydrogen bridge types, among which we found characteristic patterns. Kivonat A palládium-(szulfo)szalán modellvegyületen keresztül mutatjuk be a fém-szalén típusú komplexek egy új és egyszerű topológiai leírását. A kiválasztott koordináták, melyekkel a gerinc és a karok térállását definiáljuk, alkalmasak a szisztematikus konformáció-analízisre, ami a kevésbé kedvező konformerek megtalálását is lehetővé teszi kvantumkémiai módszerrel. A különböző vegyületek és izomerek összehasonlítása egyszerűvé válik ezen koordináták alkalmazásával.A palládium-szalán komplexeket hidrogénezési reakcióban is alkalmazzák, melyek katalitikusan aktív formája, a monohidrido-komplex több lehetséges úton is kialakulhat. A folyamat első lépésében a fenolát kar és a hidrogénmolekula szubsztitúciója valósul meg direkt, vagy egy akvakomplex intermedieren keresztül, indirekt módon. A koordinált hidrogénmolekuláról a fenolát kar oxigénjére történő közvetlen protontranszfer preferált, ami a legtöbb esetben a sebességmeghatározó lépés. Továbbá megvizsgáltuk a kialakuló hidrogén-híd típusokat, melyek közt jellegzetes mintázatokat találtunk

An acrylated isocyanonaphthalene based solvatochromic click reagent: Optical and biolabeling properties and quantum chemical modeling

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New blue light-emitting isocyanobiphenyl based fluorophores: Their solvatochromic and biolabeling properties

The preparation and optical study of 4-amino-4′-isocyanobiphenyl (ICAB) and its mono-and dialkylated derivatives (monoMICAB and diMICAB) are reported. They were found to be effective blue light emitters with a solvatochromic range of Δλmax = 104 nm, 92 nm and 90 nm, respectively. All three compounds turned out to be promising candidates in protein-labeling, yielding ∼70-190× increase in their fluorescence intensity when mixed with 10× molar excess of bovine serum albumin (BSA). The binding constants for the BSA-fluorophore complexes were found to be KICAB-BSA = 3.8 × 104 ± 5.7 × 103 M-1, KmonoMICAB-BSA = 6.0 × 104 ± 3.9 × 103 M-1 and KdiMICAB-BSA = 2.3 × 104 ± 3.2 × 103 M-1. Time resolved fluorescence measurements revealed a nearly uniform ∼2 ns lifetime for all three BSA-complexed ICAB derivatives. © 2015 Elsevier B.V. All rights reserved

Can Nonpolar Polyisobutylenes be Measured by Electrospray Ionization Mass Spectrometry? Anion-Attachment Proved to be an Appropriate Method.

Polyisobutylenes (PIBs) with different end-groups including chlorine, exo-olefin, hydroxyl, and methyl prepared from aliphatic and aromatic initiators were studied by electrospray ionization mass spectrometry (ESI-MS). Independently of the end-groups, presence or absence of aromatic initiator moiety, these PIB derivatives were capable of forming adduct ions with NO3 - and Cl- ions, thus allowing the direct characterization of these compounds in the negative ion mode of ESI-MS. To obtain [PIB + NO3]- and [PIB + Cl]- adduct ions with appreciable intensities, addition of polar solvents such as acetone, 2-propanol, or ethanol to the dichloromethane solution of PIBs was necessary. Furthermore, increasing both the polarity (by increasing the acetone content) and the ion-source temperature give rise to enhanced intensities for both [PIB + NO3]- and [PIB + Cl]- ions. Energy-dependent collision induced dissociation studies (CID) revealed that increasing the collision voltages resulted in the shift of the apparent molecular masses to higher ones. CID studies also showed that dissociation of the [PIB + Cl]- ions requires higher collision energy than that of [PIB + NO3]-. In addition, Density Functional Theory calculations were performed to gain insights into the nature of the interactions between the highly non-polar PIB chains and anions NO3 - and Cl- as well as to determine the zero-point corrected electronic energies for the formation of [PIB + NO3]- and [PIB + Cl]- adduct ions. Graphical Abstract