Search results for "Pi interaction"

A Straightforward Electroactive π-Extended Tetrathiafulvalene (exTTF) Building Block

2012

The synthesis and X-ray structure of a new and readily available exTTF derivative (6) bearing a methyltriphenylphosphonium bromide moiety as a new building block for the construction of electroactive molecules is reported. The phosphonium salt 6, which was prepared in one step from 2-hydroxymethyl-exTTF as a stable yellow solid in 84 % yield, efficiently undergoes Wittig olefination reactions with a variety of aldehydes to predominantly form the E isomer. Electronic spectra and cyclic voltammetry of the novel compounds reveal the electronic communication between the electroactive units.

Scalar ΛN and ΛΛ interactions within a chiral unitary approach

2008

We study the central part of the ΛN potential by considering the correlated and uncorrelated two-meson exchange besides the ω exchange contribution. The correlated two-meson is evaluated in a chiral unitary approach. We find that a short range repulsion is generated by the correlated two-meson potential which also produces an attraction in the intermediate distance region. The uncorrelated two-meson exchange produces a sizable attraction in all cases which is counterbalanced by ω exchange contribution.

Greatly enhanced intermolecular π-dimer formation of a porphyrin trimer radical trications through multiple π bonds.

2010

A trefoil-like porphyrin trimer linked by triphenylamine (TPA-TPZn(3)) was synthesized. A three-electron oxidation of TPA-TPZn(3) forms a radical trication (TPA-TPZn(3)(3+)), in which each porphyrin ring undergoes a one-electron oxidation. The radical trication TPA-TPZn(3)(3+) spontaneously dimerizes to afford (TPA-TPZn(3))(2)(6+) in CH(2)Cl(2) . The characteristic charge-resonance band due to the charge delocalization over the π system of (TPA-TPZn(3))(2)(6+) was observed in the NIR region. The initial oxidation potential of TPA-TPZn(3) is negatively shifted relative to that of the corresponding monomer porphyrin, which results from the stabilization of the oxidized state of TPA-TPZn(3) as…

Perfluoro-1,1′-biphenyl and perfluoronaphthalene and their derivatives as π-acceptors for anions

2015

Addition of anions to perfluorinated 1,1′-biphenyl 1 or naphthalene 2 results in a shift of the 19F NMR signals. However, any specific interaction cannot be assigned to this effect. In order to study the interaction in more detail, the salt derivatives 3 and 4 were prepared and studied by single crystal X-ray diffraction revealing weak anion–π interactions in the solid state.

Crystallographic and (spectro)electrochemical characterizations of cobalt(II) 10-phenyl-5,15-di-p-tolylporphyrin

2021

International audience; The synthesis, cyclic and rotating disk electrode voltammograms, UV-visible absorption and Xray diffraction analyses of cobalt(II) 10-phenyl-5,15-dip -tolylporphyrin (1-Co) are described. 1-Co was crystallized by slow diffusion of n-hexane into a concentrated CH2Cl2 solution. X-ray diffraction analyses reveals porphyrin aromatic cycle stacking in the crystal, C-H•••π interactions of the CH2Cl2 solvent with the π-system of one tolyl group and Co(II)•••π (porphyrin ring) interactions. The abstraction of 1.0 F/mol during the electrolysis at the first oxidation potential was followed by spectroelectrochemistry. It leads to the Co(II) → Co(III) transformation rather than …

Crystal structure of 4-{2-[4-(di­methyl­amino)­phen­yl]diazen-1-yl}-1-methyl­pyridinium iodide

2015

The molecular geometry of the ionic title compound, C14H17N4+·I−or DAZOP+·I−, is essentially featureless. Regarding the crystal structure, in addition to the obvious cation–anion Coulombic interactions, the packing is mostly directed by non-covalent interactions involving both ring systems, as well as the iodide anion. It consists of cationic molecules aligned along [101] and disposed in an antiparallel fashion while linked into π-bonded dimeric entities by a stacking contact involving symmetry-related phenyl rings, with a centroid–centroid distance of 3.468 (3) Å and a slippage of 0.951 Å. The dimers are, in addition, sustained by a number of C—H...I and I...π (I...centroid = 3.876 Å) inte…

Meson-meson interactions in a nonperturbative chiral approach

1999

A non-perturbative method which combines constraints from chiral symmetry breaking and coupled channel unitarity is used to describe the meson-meson interaction up to about 1.2 GeV. The approach uses the O(p^2) and O(p^4) chiral Lagrangians. The seven free parameters of the O(p^4) Lagrangian are fitted to the data. The results are in good agreement with a vast amount of experimental analyses. The amplitudes develop poles in the complex plane corresponding to the f0, a0, rho, K*, phi, sigma and kappa resonances; the latter two, very broad. The total and partial decay widths of the resonances are also well reproduced. Further extensions and applications of this chiral non-perturbative scheme …

Phenylethynyl- and Phenylethenylmetacyclophanes with π,π Interactions

1999

A Computational Study of Two-State Conformational Changes in 16-Electron [CpW(NO)(L)] Complexes (L=PH3, CO, CH2, HCCH, H2CCH2)

1999

International audience; High-spin and low-spin [CpW(NO) (L)] complexes are calculated to be remarkably close in energy. Several critical conformational changes in the singlet compounds are predicted to proceed more readily by spin crossover to the triplet hypersurface. The relationships between spin state, π bonding, ligand orientation, and geometry at W are explored.

Discrete supramolecular donor-acceptor complexes

2009

The renewed interest in noncovalently associating electroactive molecules arises in part from the quest for new organic materials that convert solar energy into electrical/ chemical equivalents. In this context, the formation of charge-separated states is a key prerequisite. Charge-transfer events triggered by light have been studied in supramolecular donor–acceptor systems based on hydrogen bonds and coordinative metal bonds. Although many of the most widely utilized electroactive fragments feature large pconjugated surfaces, to date the use of p–p aromatic interactions has mainly been limited to the construction of semi-infinite ensembles of chromophores either to achieve charge transport…