55 research outputs found
Computational Study of Copper(II) Complexation and Hydrolysis in Aqueous Solutions Using Mixed Cluster/Continuum Models
Quantum-chemical modeling of solvated first row transition metal ions. Solvateeritud \ufcleminekumetalli-ioonide kvantkeemiline modelleerimine
Solution- and gas-phase study of binding of ammonium and bisammonium hydrocarbons to oxacalix[4]arene carboxylate
Oxacalixarenes represent a distinctive class of macrocyclic compounds, which are closely related to the parent calixarene family, offering binding motifs characteristic of calixarenes and crown ethers. Nevertheless, they still lack extensive characterization in terms of molecular recognition properties and the subsequent practical applicability. We present here the results of binding studies of an oxacalix[4]arene carboxylate macrocycle toward a variety of organic ammonium cationic species. Our results show that the substituents attached to the guest ammonium compound largely influence the binding strengths of the host. Furthermore, we show that the characteristic binding pattern changes upon transition from the gas phase to solution in terms of the governing intermolecular interactions. We identify the key factors affecting host–guest binding efficacy and suggest rules for the important molecular structural motifs of the interacting parts of ammonium guest species and the macrocycle to facilitate sensing of ammonium cations.peerReviewe
Can Electrophilicity Act as a Measure of the Redox Potential of First-Row Transition Metal Ions?
Large Azobenzene Macrocycles : Formation and Detection by NMR and MS Methods
Azobenzene macrocycles are widely investigated as potential drug delivery systems and as part of molecular machines due to their photo-responsive properties. Herein, we detect the formation of a series of new azobenzene macrocycles that feature up to eight switchable repeating units. High-resolution mass spectrometry and ion mobility (IM) mass spectrometry experiments and 1H and diffusion-ordered spectroscopy (DOSY) NMR are used to detect the presence of the macrocycles that contain 10 to 40 aromatic rings in the gas phase and solution, respectively. The responsiveness of the Z-to-E photo-switching of the smallest of the macrocycles, exhibiting 2 azobenzene units and in total 10 aromatic rings, separated with column chromatography, is studied with irradiation experiments, using both UV-Vis light and thermal excitation and relaxation, and monitoring the sample with UV-Vis absorption and 1H NMR spectroscopy. DFT calculations are used to understand the conformation of this isolated species in solution.peerReviewe
Modelling of the initial stages of the electropolymerization mechanism of o-phenylenediamine
Spontaneous Symmetry Breaking Facilitates Metal-to-Ligand Charge Transfer: A Quantitative Two-Photon Absorption Study of Ferrocene-phenyleneethynylene Oligomers
Change
of the permanent molecular electric dipole moment, Δμ,
in a series of nominally centrosymmetric and noncentrosymmteric ferrocene-phenyleneethynylene
oligomers was estimated by measuring the two-photon absorption cross-section
spectra of the lower energy metal-to-ligand charge-transfer transitions
using femtosecond nonlinear transmission method and was found to vary
in the range up to 12 D, with the highest value corresponding to the
most nonsymmetric system. Calculations of the Δμ performed
by the TD-DFT method show quantitative agreement with the experimental
values and reveal that facile rotation of the ferrocene moieties relative
to the organic ligand breaks the ground-state inversion symmetry in
the nominally symmetric structures
Theoretical study of the mechanism of an interfacial oxygen reduction reaction in the presence of a hydrazone ligand, its cobalt (II) complex and their conjugate acids as catalyst
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