ChemPhysChem

The cover picture shows STM images of ordered two-dimensional (2D) supramolecular structures obtained by the self-assembly of two small conjugated organic molecules (DIP and F₁₆CuPc). These binary monolayers exhibit an extraordinary structural order which offers a promising avenue towards the molecular design of organic functional surfaces. In their Communication on page 1915 Barrena et al. demonstrate that the growth of these monolayers can be tailored via variation of the relative co-deposition ratio. From a fundamental point of view, this ambipolar hybrid system could serve as a model to understand non-convalent interactions in 2D supramolecular self-organisation.

The whole story: In NMR data the nuclear overhauser effect is susceptible to additional dynamic averaging phenomena. Residual dipolar couplings measured under conditions of partial molecular alignment overcome theses difficulties and provide access to direct, analytical determination of both structural and dynamics components of protein behaviour (see figure) in solution.

Gold fever: Gold turns out to be catalytically very active, provided that either one or two of the three conditions shown in the graphic are fulfilled. In CO oxidation at room temperature even unsupported gold is active in the presence of alkaline water. The active states of gold in the gold catalysts reported so far can be classified into four groups: bulk gold, nanoparticles, clusters or thin layers with specific sizes, and cations.

Self organisation: 2D binary molecular monolayers formed by co-evaporation of two small organic molecules (DIP and F₁₆CuPc), achieve exceptional order through CF⋅⋅⋅H interactions. Room temperature STM images of the “2D phase diagram” for binary structures versus the relative coverage on Au(111) and Cu(111) are shown in the figure.

Switching axis: A new banana-shaped molecule forms the SmC_AP_A phase in the ground state and SmC_SP_F phase on applying an electrical field. The optic axis of such banana-shaped molecules is oriented parallel to the rubbing direction under zero-field state. The picture shows the proposed three polar structures in the B2 phase: two different colors indicate that the mesogenic structure is asymmetric.

Crystal lattice dynamics: By studying the low-energy intermolecular vibrational modes in the far-infrared region it is possible for the first time to resolve the two-step solid-state conversion mechanism in carbamazepine polymorphic forms III and I directly (see picture).

Two ways in! A spectroscopic study of the properties of the two principal insertion sites of single dibenzoterrylene molecules in anthracene single crystals is performed at cryogenic temperatures. Molecular dynamics simulations agree well with spectroscopic results and show that one dibenzoterrylene molecule replaces three anthracene molecules (see figure).

Polaron destabilization in highly stacked regioregular poly(3-hexythiophene-2,5-diyl) reflects high charge-carrier mobility. This is indicated by the narrowing of two-photon photoemission spectroscopy profiles with increasing thickness (see picture).

Multiple-chromophore excitation affecting the yield and lifetime of charge-separated states (see picture) can be produced by irradiation of multicomponent systems with medium-intensity nano- and picosecond laser pulses.

Analysis of intramolecular hydrogen bonds (IMHB) in different enols of derivatives of cyclobutane, cyclobutene, and cyclobutadiene bearing oxygen and nitrogen functionalities (see image) shows that, quite unexpectedly, when the functionality exhibiting the IMHB is unsaturated, the IMHB is weaker than in the saturated counterparts, verifying that the primary effect on the strength of the IMHB is not resonance.

A series of snapshots obtained by molecular dynamics simulations, determine the proton-transfer (PT) mechanism of microsolvated phenylalanine Phe⋅(H₂O)_n (shown for n=2). Starting from the initial structure (left), the system passes through a transition state (TS) for concerted triple PT, a zwitterionic structure, and a TS for reverse PT to form the final product (right).

Structure–reactivity relationships in hydrogen transfer reactions are elucidated by density functional theory and the hybrid complete basis set (CBS) method. For exothermic reactions, the activation energy increases as the reaction becomes more exothermic (see figure). This contra-thermodynamic behavior is explained by pre-reactive hydrogen bonding complexes.

Calculation on target: First principle calculations of the crystal structures, electronic, dielectric and vibrational properties of NaH, Na₂O and NaOH are reported. The obtained computational results predict that the dehydrogenation reaction, NaH+NaOH→H₂+Na₂O, takes place at 528 K, which is in agreement with the experimentally observed value (see figure).

Sodium phosphate tellurite glasses prepared and structurally characterized by XP and NMR spectroscopies, show no new structural units and no sharing of the network modifier. The resulting chemical segregation leads to a nonrandom sodium distribution. The picture shows the fraction of different linkages in a (NaPO₃)_x(TeO₂)_1−x glass.

Loss of capacity: CuFe₂O₄ samples are tested as electrode materials for lithium-ion batteries. Capacity fading is related to the detachment of metallic particles from the starting material, observed by high-resolution transmission electron microscopy (see image), and the growth of metallic iron aggregates on subsequent cycling, as detected by ⁵⁷Fe Mössbauer spectroscopy.

Single manganese ions are located in the bulk interior of Mn-doped ZnSe (ZnSe:Mn) nanoparticles, according to studies by X-ray magnetic circular dichroism (XMCD). This method is a powerful tool for exploring the local electronic environment of transition-metal ions and for the quantitative investigation of their magnetic properties. The picture shows the XMCD spectrum and a schematic of a single particle with stabilizing organic ligands (green).

Micelles or Vesicles? Single-tailed surfactants have been associated with various organic counterions. Depending on the structure of the ion-paired surfactant, a micelle-to-vesicle transition is observed (see picture), thus demonstrating the key role played by the positioning of the counterion in supramolecular self-assembly.