Regimes of water droplet evaporation on copper substrates

Distilled water droplet evaporation has been studied on copper substrate surfaces with different degrees of roughness. Data on variations in the contact diameter have been employed to distinguish between the regimes of distilled water droplet spreading over the copper surfaces that proceed after the viscous regime. For each isolated regime, the duration has been determined as a fraction of the total evaporation time and the main physical processes have been described. Variations in contact angles have been analyzed as depending on copper surface temperature. It has been established that, as the substrate temperature is elevated, wetting becomes better, while the adhesion work remains almost unchanged, thereby indicating the absence of chemical and structural transformations at the liquid–substrate interface.     

Dissociation of the N-C(alpha) bond and competitive formation of the [z(n) - H](+) and [c(n) + 2H](+) product ions in radical peptide ions containing tyrosine and tryptophan: the influence of proton affinities on product formation

Dissociations at the N-C_α bond of tryptophan and tyrosine residues are the prevalent pathways in the fragmentations of radical cations of tripeptides that contain such as residues. This process involves a proton transfer from the β-carbon of the tryptophan or tyrosine residue to the carbonyl oxygen of the amide group, followed by cleavage of the N-C_α bond, generating low-lying proton-bound dimers that dissociate to give each an ionic and a neutral product. Formation of the [z _n −H]^∢+ or [c _n +2H]⁺ ion is a competition between the two incipient fragments for the proton in a dissociating proton-bound dimer.     

Catalytic oxidation of H2 by N2O in the gas phase: O-atom transport with atomic metal cations

Twenty-five atomic cations, M (+), that lie within the thermodynamic window for O-atom transport catalysis of the oxidation of hydrogen by nitrous oxide, have been checked for catalytic activity at room temperature with kinetic measurements using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. Only 4 of these 25 atomic cations were seen to be catalytic: Fe (+), Os (+), Ir (+), and Pt (+). Two of these, Ir (+) and Pt (+), are efficient catalysts, while Fe (+) and Os (+) are not. Eighteen atomic cations (Cr (+), Mn (+), Co (+), Ni (+), Cu (+), Ge (+), Se (+), Mo (+), Ru (+), Rh (+), Sn (+), Te (+), Re (+), Pb (+), Bi (+), Eu (+), Tm (+), and Yb (+)) react too slowly at room temperature either in their oxidation with N 2O to form MO (+) or in the reduction of MO (+) by H 2. Many of these reactions are known to be spin forbidden and a few actually may lie outside the thermodynamic window. Three alkaline-earth metal monoxide cations, CaO (+), SrO (+), and BaO (+), were observed to favor MOH (+) formation in their reactions with H 2. A potential-energy landscape is computed for the oxidation of H 2 with N 2O catalyzed by Fe (+)( (6)D) that vividly illustrates the operation of an ionic catalyst and qualitatively accounts for the relative inefficiency of this catalyst.     

Radical-cationic gaseous amino acids: a theoretical study

Three major forms of gaseous radical-cationic amino acids (RCAAs), keto (COOH), enolic (C(OH)OH), and zwitterionic (COO(-)), as well as their tautomers, are examined for aliphatic Ala(.+), Pro(.+), and Ser(.+), sulfur-containing Cys(.+), aromatic Trp(.+), Tyr(.+), and Phe(.+), and basic His(.+). The hybrid B3LYP exchange-correlation functional with various basis sets along with the highly correlated CCSD(T) method is used. For all RCAAs considered, the main stabilizing factor is spin delocalization; for His(.+), protonation of the basic side chain is equally important. Minor stabilizing factors are hydrogen bonding and 3e-2c interactions. An efficient spin delocalization along the N-C(alpha)-C(O-)O moiety occurs upon H-transfer from C(alpha) to the carboxylic group to yield the captodative enolic form, which is the lowest-energy isomer for Ala(.+), Pro(.+), Ser(.+), Cys(.+), Tyr(.+), and Phe(.+). This H-transfer occurs in a single step as a 1,3-shift through the sigma-system. For His(.+), the lowest-energy isomer is formed upon H-transfer from C(alpha) to the basic side chain, which results in a keto form, with spin delocalized along the N-C(alpha)-C=O fragment. Trp(.+) is the only RCAA that favors spin delocalization over an aromatic system given the low ionization energy of indole. The lowest-energy isomer of Trp(.+) is a keto form, with no H-transfer.     

The thermodynamic characteristics of formation of copper(II) ion complexes with carboxylic acids in aqueous solutions

The heat effects of complex formation between copper(II) ions and malonic, maleic, and succinic acids were measured in an isothermic-shell calorimeter at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solutions were calculated.     

Molecular and supramolecular organization of star-shaped C60-fullerene-containing polyethylene oxide in benzene

The molecular properties and self-organization of star-shaped fullerene-containing polyethylene oxide in benzene were studied by methods of molecular hydrodynamics and small-angle neutron scattering.     

Photophysical manifestations of interactions of quantum dots with ortho-phenanthroline molecules

The interaction of CdSe/ZnS nanocrystals (NCs) (solubilized by trioctylphosphine oxide (TOPO) molecules) with ortho-phenanthroline (OP) molecules has been investigated. It is shown that OP molecules can replace TOPO; in this case, bonding of OP molecules with the nanocrystal surface does not lead to the formation of NC aggregates. It is established that the difference in the evolution of the spectral-luminescence NC characteristics in a mixture with OP is independent of the NC size. A model of the interaction of NCs with OP molecules is proposed.     

Uranyl complexes with ethylmethylglyoxime

Uranyl complexes with ethylmethylglyoxime were studied. The structure of (CN₃H₆)₄[(UO₂)₂(CO₃)(C₂O₄)₂(C₅H₈N₂O₂)] · 1.5H₂O was determined by X-ray crystallography. The structure of the complex is binuclear with a double carbonate dioximate bridging fragment.     

A new synthesis of phthalimidines

A new synthesis of phthalimidines is described. 3-Acyloxy-2-aryl- and 2-acylamino-3-acyloxyphthalimidines were prepared by the reaction of 3-arylaminophthalides or o-formylbenzoic acid acylhydrazones with acetic or propionic anhydrides. Their reactions with O-, N-, S-, and C-nucleophiles were studied. The structure of 2-acetyl(cyanoacetyl)amino-3-acetoxyindolin-1-one was confirmed by X-ray diffraction analysis.