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Using ab initio approaches accounting for environmental effects, we investigate the ground- and excited-state properties of four subporphyrinoids: subporphyrin, subporphyrazine, tribenzosubporphyrin, and subphthalocyanine. We first show that the selected level of theory, that is DFT(PBE0), is able to reproduce the structure and NMR spectra of all compounds. The aromaticity of these four macrocyclic entities are next quantified and it is showed that these bowl-shape induced molecules present very strong aromatic characters. Next we analyze the spectral signatures of all four compounds using an approach going beyond the vertical approximation. The 0-0 energies are reproduced with a mean absolute deviation smaller than 0.1 eV, and the very good agreement obtained between experimental and theoretical band shapes allows us to unravel the vibronic contributions responsible to the specific band shapes of these subporphyrinoids. Finally, we investigate a large series of substituted subporphyrins, demonstrate the quality of the trends that are obtained with theory and design new compounds presenting red-shifted optical bands.

The unprecedented N-pyridin-2-yl substituted benzo(thio)amides were prepared and subsequently converted into the cyclic difluoroboranyl (BF2) derivatives. Mass spectrometry, multinuclear NMR, IR, and elemental analysis confirmed the structure of these compounds. UV/vis and fluorescence spectroscopy as well as first-principle calculations were used to study their properties. For the first time, the influence of both the O/S replacement and presence/absence of the BF2 moiety on the photophysical properties of compounds exhibiting charge transfer properties were examined experimentally and theoretically. We show that the sulfur-containing compound has a much smaller emission quantum yield than its oxygen counterpart. The fluorescence quantum yield is much higher upon formation of the difluoroboranyl complex.

We have previously shown that a 28-amino acid peptide derived from the BRC4 motif of BRCA2 tumor suppressor inhibits selectively human RAD51 recombinase (HsRad51). With the aim of designing better inhibitors for cancer treatment, we combined an in silico docking approach with in vitro biochemical testing to construct a highly efficient chimera peptide from eight existing human BRC motifs. We built a molecular model of all BRC motifs complexed with HsRad51 based on the crystal structure of the BRC4 motif-HsRad51 complex, computed the interaction energy of each residue in each BRC motif, and selected the best amino acid residue at each binding position. This analysis enabled us to propose four amino acid substitutions in the BRC4 motif. Three of these increased the inhibitory effect in vitro, and this effect was found to be additive. We thus obtained a peptide that is about 10 times more efficient in inhibiting HsRad51-ssDNA complex formation than the original peptide.

X-ray photoelectron spectroscopy at 3.5 keV photon energy, in combination with high-resolution transmission electron microscopy, is used to follow the formation of the interface between rhodium and carbon nanotubes. Rh nucleates at defect sites, whether initially present or induced by oxygen-plasma treatment. More uniform Rh cluster dispersion is observed on plasma-treated CNTs. Experimental results are compared to DFT calculations of small Rh clusters on pristine and defective graphene. While Rh interacts as strongly with the carbon as Ti, it is less sensitive to the presence of oxygen, suggesting it as a good candidate for nanotube contacts.

A combined experimental and theoretical approach is used to define astatine (At) speciation in acidic aqueous solution and to answer the two main questions raised from literature data: does At(0) exist in aqueous solution and what is the chemical form of At(+III), if it exists. The experimental approach considers that a given species is characterized by its distribution coefficient (D) experimentally determined in a biphasic system. The change in speciation arising from a change in experimental conditions is observed by a change in D value. The theoretical approach involves quasi-relativistic quantum chemistry calculations. The results show that At at the oxidation state 0 cannot exist in aqueous solution. The three oxidation states present in the range of water stability are At(-I), At(+I), and At(+III) and exist as At(-), At(+), and AtO(+), respectively, in the 1-2 pH range. The standard redox potentials of the At(+)/At(-) and AtO(+)/At(+) couples have been determined, the respective values being 0.36 +/- 0.01 and 0.74 +/- 0.01 V vs NHE.

Two bisphosphonate adaptors were designed to immobilize histidine-tagged proteins onto glass substrates coated with a zirconium phosphonate monolayer, allowing efficient and oriented immobilization of capture proteins, affitins directed to lysozyme, on a microarray format. These bifunctional adaptors contain two phosphonic acid anchors at one extremity and either one nitrilotriacetic acid (NTA) or two NTA groups at the other. The phosphonate groups provide a stable bond to the zirconium interface by multipoint attachment and allow high density of surface coverage of the linkers as revealed by X-ray photoelectron spectroscopy (XPS). Reversible high-density capture of histidine-tagged proteins is shown by real-time surface plasmon resonance enhanced ellipsometry and in a microarray format using fluorescence detection of AlexaFluor 647-labeled target protein. The detection sensitivity of the microarray for the target protein was below 1 nM, despite the monolayer arrangement of the probes, due to very low background staining, which allows high fluorescent signal-to-noise ratio. The performance of these Ni-NTA-modified zirconium phosphonate coated slides compared favorably to other types of microarray substrates, including slides with a nitrocellulose-based matrix, epoxide slides, and epoxide slides functionalized with Ni-NTA groups. This immobilization strategy has a large potential to fix any histidine-tagged proteins on zirconium or titanium ion surfaces.

The first peripheral postfunctionalization of a hyperbranched polyimide by nonlinear optic chromophores (DR1 derivative) was achieved using two different routes. The first one consists in the esterification of the terminal carboxylic acid groups, whereas the second is based on copper-catalyzed Huisgen reaction of the terminal propargylic ester groups. The resulting polymers display good solubility in classical organic solvents and good filmability because thick films can be prepared (up to 2.7 mum). The second-order nonlinear optical properties were measured by SHG at 1064 nm and we show that these hyperbranched polymers exhibit good poling efficiency and good thermal stability since the electro-optic activity remains stable up to 130 degrees C. These results illustrate the potential of hyperbranched polymers to host second-order nonlinear optical chromophores to replace dendrimers or classical linear polymers generally used in this area.

We study the structure and vibrational modes of a wide range of oxohalides of vanadium (VOX(n)Y(m); X, Y = F, Cl, Br, I; n, m = 0-3, n + m < or = 3). The results agree well with experimental results for VOCl(3) and VOF(3) and suggest reassignment of the experimentally observed VOF to VOF(2). We provide new assignments for various experimental modes, identifying several intermediates (VOBr(2), VOBr) and mixed structures (e.g., VOCl(2)Br), and discuss formation trends and stabilities.

A new heterometallic dyad composed of a zinc porphyrin linked by bisethynyl quaterthiophene to a gold porphyrin was synthesized according to a stepwise modular approach. The latter dyad and the parent reference compounds (porphyrin-ethynylquaterthiophene) were characterized by electrochemistry, spectroelectrochemistry, and femtosecond transient absorption spectrocopy. We showed that light excitation of the zinc or the gold porphyrin induces a very fast and quantitative charge separation over a distance of 25 A which occurs through a superexchange mechanism. The lifetime of the charge-separated state is 3.3 ns in toluene and 100 ps in dichloromethane, and it recombines to the ground state in both solvents.

The excellent photochromic properties of (H(2)DABCO)(2)(HDMA)(0.5)Na(0.75)(H(3)O)(0.75)[Mo(8)O(27)] x 3 H(2)O (4), a new member of the (H(2)DABCO)(2)(A)(x)[Mo(8)O(27)] x n H(2)O series, are compared with those of (H(2)DABCO)(2)(NH(4))(2)[Mo(8)O(27)] x 4 H(2)O (1), (H(2)DABCO)(2)(H(2)pipz)[Mo(8)O(27)] (2), and (H(2)pipz)(3)[Mo(8)O(27)] (3). All these powdered materials turn from white to purple under illumination at 365 nm, which is associated with photoreduction of Mo(6+) cations into Mo(5+) cations. We show that the rates of coloration, which increase in the order 1 < 3, 2 < 4, are related to the decrease in the concentration of reducible Mo(6+) centers with irradiation time and follow a second-order reaction law because the event of light absorption at a reducible Mo(6+) site does not necessarily coincide with that of the N(+)-H bond breaking in the N(+)-H...O hydrogen bond associated with the Mo(6+) site. First-principles density functional electronic structure calculations were carried out to find that this trend correlates with the homolytic dissociation energies of the N(+)-H bonds in the organic cations HDMA(+), H(2)pipz(2+), H(2)DABCO(2+), and NH(4)(+). This observation is consistent with a photochromic mechanism based on the homolytic cleavage of N(+)-H bonds rather than on the heterolytic cleavage of N(+)-H bonds.

Recent ultrafast methods make it possible to obtain two-dimensional (2D) nuclear magnetic resonance (NMR) spectra in a fraction of a second. This paper presents the first evaluation of ultrafast 2D NMR for quantitative analysis. On the basis of optimized conditions presented in recent studies, two homonuclear ultrafast techniques, J-resolved spectroscopy and TOCSY, are evaluated on model mixtures in terms of repeatability, long time stability, and linearity. The results are compared to conventional 1D (1)H NMR spectroscopy. Repeatabilities better than 1% for ultrafast J-resolved spectra and better than 7% for TOCSY spectra are obtained. The long-term stability is better than 4% for J-resolved spectroscopy and between 2% and 11% for TOCSY. Moreover, both methods are characterized by excellent linearities. This new analytical method opens important perspectives for fast, precise, and accurate quantitative analysis of complex mixtures and for the quantitative study of short time scale phenomena.

Among microalgae, the marine diatom Haslea ostrearia has the distinctive feature of synthesizing and releasing, into the surrounding environment, a blue-green polyphenolic pigment called marennine. The oyster-breeding industry commonly makes use of this natural phenomenon for the greening of oysters grown in the ponds of the French Atlantic coast. This article reports the in vitro antioxidant properties of pure marennine. Two kinds of evaluation systems were adopted to test the antioxidative activity of marennine: antioxidant capacity assays (beta-carotene and thymidine protection assays and iron reducing power assay) and free radical scavenging assays (DPPH*, O2*-, and HO*). In almost all cases, marennine exhibited significantly higher antioxidative and free radical scavenging activities than natural and synthetic antioxidants commonly used in food, as shown by comparing median effective concentration (EC 50) values, for each test independently. This medium molecular weight polyphenol (around 10 kDa) from microalgae is thus a potentially useful natural antioxidant. Because of its blue-coloring property and water solubility, it could also be used as a natural food-coloring additive.

The synthesis of the fluorinated 4,5-(2,2'-difluoropropylenedithio)-1,3-dithiol-2-one heterocycle with DAST allows for the preparation of several symmetrical and unsymmetrical di- and tetrafluoro-substituted tetrathiafulvalenes with accessible oxidation potentials (0.6 < E1(1/2) < 0.85 V vs SCE) despite the presence of the electron-withdrawing CF2 groups. The flexibility of the fluorinated seven-membered ring identified from room-temperature NMR data has been thoroughly investigated by temperature-variable 1H and 19F NMR experiments, allowing for the identification of two independent folding processes, whose coalescence temperatures (Tc) and activation energies (deltaGdouble dagger) were determined (Tc = -15 degrees C, deltaGdouble dagger = 50.2 kJ mol(-1) and Tc = 47 degrees C, deltaGdouble dagger = 51.1 kJ mo(-1)). The analysis of the X-ray crystal structures of three of those fluorinated TTF demonstrates the efficiency of the nonbonded fluorine exclusion interactions for the stabilization of layered structures with fluorous bilayers, together with S...S van der Waals interactions and C-H...F hydrogen bonds.