Monomeric and polymeric copper and zinc tripyrrins

Neutral transition metal complexes of different alpha,omega-dimethyltripyrrins TrpyMX with M = Cu(II) and Zn(II) have been prepared with a variety of anionic halogeno and pseudohalogeno ligands X, and have been studied with respect to coordination modes and structural distortion. Only four- and five-coordinate species have been observed throughout the series. All four-coordinate species display unstrained, but distorted tetrahedral or strained and distorted square-planar coordination environments for zinc(II) and copper(II) species, respectively, thus following the expectations from simple ligand field arguments. Five-coordinate species do not form easily and were observed either in donor solvents or in the solid as 1D coordination polymers with distorted trigonal-bipyramidal coordination and different topologies.     

Structure and dynamics of beta-cyclodextrin in aqueous solution at the density-functional tight binding level

Structure and dynamics of beta-cyclodextrin (beta-CyD), a prototype host for inclusion compounds of biological interest, is investigated by means of density-functional based tight-binding molecular dynamics (MD) simulations. The computational protocol is benchmarked against available experimental data and first-principles calculations. Solvent-solute interactions, including the diffusion into and dwell time of the solvent in the cavity of beta-CyD, are studied with a hybrid QM/MM method. Comparison of MD simulations of beta-CyD in the gas phase and in water shows that the solvent reduces the flexibility of the structure framework, while the terminal hydroxyl groups become more flexible and are embedded in a network of hydrogen bonds. Our 160 ps MD simulations, provide enough sampling to discuss the dynamics of the water inside the cavity. The dwell time of the encapsulated water molecule has a wide distribution with a peak at 70 fs. Surprisingly, despite only the 17% difference between the "top" and "bottom" opening area of the beta-CyD cone, 64% of the water molecules enter the cavity through the slightly bigger "bottom" aperture.     

Site-specific incorporation of glycosylated serine and tyrosine derivatives into proteins

Glycosylation of proteins can have a dramatic effect on their physical, chemical, and biological properties. Analogues of dihydrofolate reductase and firefly luciferase containing glycosylated amino acids at single, predetermined sites have been elaborated. Misacylated suppressor tRNAs activated with glycosylated serine and tyrosine derivatives were used for suppression of the nonsense codons in a cell-free protein biosynthesizing system, thereby permitting the preparation of the desired glycosylated proteins. In this fashion, it was possible to obtain proteins containing both mono- and diglycosylated amino acids, including glycosylated serine and tyrosine moieties. For the modified firefly luciferases, the effect of these substitutions on the wavelength of the light emitted by firefly luciferase was investigated. The maximum wavelength for mutants containing peracetylated glycosylated serine derivatives at position 284 showed a red shift in the emission spectra. For mutants containing glycosylated tyrosines, the red shift was observed only when the carbohydrate moiety was fully deacetylated.     

DFT and local MP2 study of switching process in a pH controllable molecular “shuttle”

A pH controllable molecular “shuttle,” comprising of dibenzo 24 crown‐8 (DB24C8) macroring bound to a “finger” molecule possessing two different recognition sites has been studied at the density functional theory (DFT) and Møller‐Plesset second‐order (MP2) levels of theory. The calculation confirmed experimental results that translational conformer with DB24C8 located around NH station has the lowest energy, while the conformer with DB24C8 located around NH station shows the highest energy. It has been found that Bpym2+ unit consists of two “substations” separated by an energy barrier of 3–17 kcal/mol depending on the state of the NH–NH station. The translational conformers are stabilized by NH…O, ⁺NH…O, ⁺NCH…OH‐bonds, and π–π stacking with different contributions, depending on the conformer type. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem 2007     

High harmonic generation and molecular orbital tomography in multielectron systems

High harmonic radiation is produced when atoms or molecules are ionized by an intense femtosecond laser pulse. The radiated spectrum has been shown experimentally to contain information on the electronic structure of the molecule, which can be interpreted as an image of a single molecular orbital. Previous theory for high harmonic generation has been limited to the single-active-electron approximation. Utilizing semisudden approximation, the authors develop a theory of the recombination step in high harmonic generation and tomographic reconstruction in multielectron systems, taking into account electron spin statistics and electron-electron correlations within the parent molecule and the ion. They show that the resulting corrections significantly modify the theoretical predictions, and bring them in a better agreement with experiment. They further show that exchange contributions to harmonic radiation can be used to extract additional information on the electronic wave function.     

New hexamethine–hemicyanine dyes for the development of integrated optochemical sensors

New far-visible absorbing anilino-cyanine dyes have been synthesised for future application as chromoionophores in integrated waveguide absorbance optodes based on bulk optodes. The effect of the heterocycle, of the substitution of the heterocyclic nitrogen and of the type of heptamethine central ring on the pK _a values (4.3–8.2 in ethanol–water solutions and 9.5–11.0 in plasticised PVC membranes), on the spectroscopic characteristics of the dye and on photostability is discussed. pH-selective bulk optodes have been formulated as a first approach to develop ion-selective optodes, and sensitivity, repeatability, lifetime and response time have been determined. The dyes show good analytical behaviour for use as chromoionophores for the development of ion-selective optodes. Reversible (80–87%), fast (tr_90% = 0.94–2.28 min) and pH-sensitive membranes (slopes of 0.09–0.23 ΔAbs·pHdec^–1, absorbance range 0.19–0.53) have been obtained. Moreover, they exhibit good spectroscopic features for employment with integrated optochemical sensors: absorption maxima of the acidic species in plasticised PVC membranes matched those of 650–670-nm LEDs, high molar absorption coefficients ( L mol^–1 cm^–1 and L mol⁻¹ cm⁻¹) and fluorescence. Absorption spectra of the acidic and basic structures of one of the synthesised chromoionophores at different pKa values. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Weighted Korn inequalities for thin-walled elastic structures

Appropriate weighted norms in H¹ are presented such that the Korn type inequality is asymptotically sharp with respect to relative thickness and stiffness of the elastic plates. The weights depend crucially on the geometric structure of the plates' junction. To cite this article: O.V. Izotova et al., C. R. Mecanique 334 (2006).     

Pseudohalogeno Complexes of Sterically Hindered Tripyrrinatopalladium (TrpyPd) Fragments

Eight new pseudohalogeno complexes of sterically hindered TrpyPd fragments 4 – 11 have been prepared by salt metathesis in one step from known trifluoroacetates TrpyPdOAc^F 1 – 3 , using sodium salts of N₃, NCO, NCS, NCSe, dicyanamide (dca) and tricyanomethanide (tcm) anions. Despite the propensity of the co‐ligands to bind to two or more metal centres in a bridging coordination mode all new complexes have been shown by NMR spectroscopy to be essentially monomeric in solution. X‐ray diffraction studies performed on TrpyPdNCS( 6 ), TrpyPddca( 8 ), TrpyPddca( 9 ), and TrpyPdtcm( 10 ) revealed the presence of two different conformers in the solid state, one with a helically distorted Trpy backbone for 6 and 10 , and one with an almost planar tripyrrole but a tetrahedral distortion of the Pd^II coordination, a so‐called pseudoplanar form, for 8 and 9 . Interestingly the helical forms are also detected by unusual wavenumbers for the ν_CN stretching bands in their IR spectra. The reason for the occurrence of two different conformers in the solid state appears to be the crystal packing which depends mainly on the shape of the anionic co‐ligand and on the presense of alkyl groups on the TrpyPd fragment.     

Norm expansion along a zero variety

The reproducing kernel function of a weighted Bergman space over domains in Cd is known explicitly in only a small number of instances. Here, we introduce a process of orthogonal norm expansion along a subvariety of (complex) codimension 1, which also leads to a series expansion of the reproducing kernel in terms of reproducing kernels defined on the subvariety. The problem of finding the reproducing kernel is thus reduced to the same kind of problem when one of the two entries is on the subvariety. A complete expansion of the reproducing kernel may be achieved in this manner. We carry this out in dimension d=2 for certain classes of weighted Bergman spaces over the bidisk (with the diagonal z₁=z₂ as subvariety) and the ball (with z₂=0 as subvariety), as well as for a weighted Bargmann-Fock space over C² (with the diagonal z₁=z₂ as subvariety).