Description of excited states in [Re(Imidazole)(CO)3(Phen)]+ including solvent and spin‐orbit coupling effects: Density functional theory versus multiconfigurational wavefunction approach

The low‐lying electronic excited states of [Re(imidazole)(CO)₃(phen)]⁺ (phen = 1,10‐phenanthroline) ranging between 420 nm and 330 nm have been calculated by means of relativistic spin‐orbit time‐dependent density functional theory (TD‐DFT) and wavefunction approaches (state‐average‐CASSCF/CASPT2). A direct comparison between the theoretical absorption spectra obtained with different methods including SOC and solvent corrections for water points to the difficulties at describing on the same footing the bands generated by metal‐to‐ligand charge transfer (MLCT), intraligand (IL) transition, and ligand‐to‐Ligand‐ charge transfer (LLCT). While TD‐DFT and three‐roots‐state‐average CASSCF (10,10) reproduce rather well the lowest broad MLCT band observed in the experimental spectrum between 420 nm and 330 nm, more flexible wavefunctions enlarged either by the number of roots or by the number of active orbitals and electrons destabilize the MLCT states by introducing IL and LLCT character in the lowest part of the absorption spectrum. © 2016 Wiley Periodicals, Inc.     

A Facile Molecular Precursor‐based Synthesis of Ag2Se Nanoparticles and Its Composites with TiO2 for Enhanced Photocatalytic Activity

The reactions of different silver(I) reagents AgX (X^?=iodide, trifluoroacetate, triflate) with selenoethers R₂Se (R=Me, tBu) in a variety of solvents were investigated in relation with their use as precursors for Ag₂Se nanomaterials. Different reaction conditions led to different reactivities and afforded either molecular complexes or metal selenide nanoparticles. The reactions leading to in situ formation of the metal selenide nanoparticles were then extended in the presence of commercial TiO₂ (P25) to prepare silver selenide–titania nanocomposites with different Ag/Ti ratios. These nanocomposites, well characterized by elemental analysis (Ag, Se), PXRD, TEM, BET, XPS and UV/Vis studies, were investigated as photocatalysts for the degradation of formic acid (FA) solution. The xAg₂Se‐TiO₂ nanocomposites (x=0.01, 0.13 and 0.25 mol %) exhibited a much higher catalytic activity as compared to P25, which is an established benchmark for the photocatalysis under UV light, and retained a good photocatalytic stability after recycling for several times.     

Theoretical and Experimental Study on Boron β‐Diketonate Complexes with Intense Two‐Photon‐Induced Fluorescence in Solution and in the Solid State

Three boron diketonate chromophores with extended π‐conjugated backbone were prepared and their spectroscopic features were investigated through a combined theoretical/experimental study. It was shown that these complexes, which undergo very large electronic reorganization upon photoexcitation, combine large two‐photon absorption cross section with an emission energy and quantum efficiency in solution that is strongly dependent on solvent polarity. The strong positive influence of boron complexation on the magnitude of the two‐photon absorption was clearly established, and it was shown that the two‐photon absorption properties were dominated by the quadrupolar term. For one of the synthesized compounds, intense one‐ and two‐photon‐induced solid‐state emission (fluorescence quantum yield of 0.65 with maximum wavelength of 610 nm) was obtained as a result of antiparallel J‐aggregate crystal packing.     

Darobactins Exhibiting Superior Antibiotic Activity by Cryo-EM Structure Guided Biosynthetic Engineering**

Over recent decades, the pipeline of antibiotics acting against Gram-negative bacteria is running dry, as most discovered candidate antibiotics suffer from insufficient potency, pharmacokinetic properties, or toxicity. The darobactins, a promising new small peptide class of drug candidates, bind to novel antibiotic target BamA, an outer membrane protein. Previously, we reported that biosynthetic engineering in a heterologous host generated novel darobactins with enhanced antibacterial activity. Here we utilize an optimized purification method and present cryo-EM structures of the Bam complex with darobactin 9 (D9), which served as a blueprint for the biotechnological generation of twenty new darobactins including halogenated analogs. The newly engineered darobactin 22 binds more tightly to BamA and outperforms the favorable activity profile of D9 against clinically relevant pathogens such as carbapenem-resistant Acinetobacter baumannii up to 32-fold, without observing toxic effects.     

Solar purification and potabilization of water containing dyes

Organic pollutant removal is the main field of water photocatalytic decontamination. Molecules such as pesticides (herbicides, insecticides, fungicides, etc.) or dyes are totally destroyed and mineralized into CO₂ and innocuous inorganic anions (Cl^?, SO ₄ ^2? , NO ₃ ^? ). Presently, two azo-dyes (i.e., containing the-N=N-azo group), Cibacron Brilliant Red 3B-A and Remazol Black B (Reactive Black 5), were successfully destroyed and totally mineralized. The stoichiometric coefficients of the total degradation, as well as the mass balances have been established with different analytical tools: TOC for carbon, DCO for oxygen, ionic-HPLC for heteroatoms (N, S, P) and pH-metry for hydrogen. Moreover, nitrogen balance has been established during the photocatalytic degradation of the dyes by considering not only nitrate and ammonium ions in the solution, but also the formation of N₂ in the gas phase. The quantification of N₂ molecules suggests that the photocatalytic degradation of azo-compounds is 100% selective in generating gaseous dinitrogen. The reaction mechanism was first determined in a laboratory photoreactor, before degradation in larger pilot solar photoreactors, using UV-A radiant flux from the sun in a new sub-discipline called heliophotocatalysis.     

Spectroscopy of Ru(II) polypyridyl complexes used as intercalators in DNA: Towards a theoretical study of the light switch effect

The absorption spectroscopy of [Ru(phen)₂dppz]²⁺ and [Ru(tap)₂dppz]²⁺ (phen = 1,10-phenanthroline, tap = 1,4,5,8-tetraazaphenanthrene; dppz = dipyridophenazine) complexes used as molecular light switches by intercalation in DNA has been analysed by means of Time-Dependent Density Functional Theory (TD-DFT). The electronic ground state structures have been optimized at the DFT (B3LYP) level of theory. The absorption spectra are characterized by a high density of excited states between 500 nm and 250 nm. The absorption spectroscopy of [Ru (phen)₂dppz]²⁺ in vacuum is characterized by metal-to-ligand-charge-transfer (MLCT) transitions corresponding to charge transfer from Ru(II) either to the phen ligands or to the dppz ligand with a strong MLCT () absorption at 411 nm. In contrast, the main feature of the lowest part of the vacuum theoretical spectrum of [Ru(tap)₂dppz]²⁺ between 522 nm and 400 nm is the presence of various excited states such as MLCT (), ligand-to-ligand-charge-transfer LLCT () or intra-ligand IL () states. When taking into account solvent corrections within the polarizable continuum model (PCM) approach (H₂O, CH₃CN) the absorption spectrum of [Ru(tap)₂dppz]²⁺ is dominated by a strong absorption at 388 nm (CH₃CN) or 390 nm (H₂O) assigned to a ¹IL () corresponding to a charge transfer from the outside end of the dppz ligand to the site of coordination to Ru(II). These differences in the absorption spectra of the two Ru(II) complexes have dramatic effects on the mechanism of deactivation of these molecules after irradiation at about 400 nm. In particular, the electronic deficiency at the outside end of the dppz ligand created by absorption to the ¹IL state will favour electron transfer from the guanine to the Ru(II) complex when it is intercalated in DNA.     

Comparison of two innovatives approaches for bacterial detection: paramagnetic nanoparticles and self-assembled multilayer processes

Transfusion medicine is a field that has developed in the second half of the last century. Very rapidly, however, it became clear that this approach also carried its problems, such as the incompatibility of red blood cells and plasma between donors and recipients, and the possibility of transmitting viral and bacterial infections. An immunomagnetic biosensor for the label-free detection of a bacterial model, Escherichia coli, is described and compared to a self assembled multilayer system reported previously. The paramagnetic nanoparticles layer attracted to, and formed on, the gold electrode surface via a magnetic field up to 300 mT is not totally blocking for the redox probe comparing to the thiol self assembled monolayer (a biotin thiol and a spacer thioalcohol). Moreover, the modeling of the Nyquist spectra obtained by electrochemical impedance spectroscopy for increasing concentrations of E. coli shows for both system a sigmoid variation of the polarization resistance with increasing logarithmic concentration of bacteria. A sensitivity slope of 10.675 was obtained for the immunomagnetic sensor compared to 6.832 for the self assembled multilayer process, this indicating the higher sensitivity of the paramagnetic nanoparticles biosensor.     

Novel neutral imidazole-lipophosphoramides for transfection assays

New helper lipids, possessing an imidazole polar head, have been synthesized and included in formulations for transfection assays; these new helper lipids can improve the transfection by a factor of up to 100 compared to the use of DOPE as co-lipid.     

Stable near-infrared anionic polymethine dyes: structure, photophysical, and redox properties

The concept of cyanine has been successfully extended to an anionic heptamethine dye featuring tricyanofuran (TCF) moieties in terms of structure, reactivity, and photophysical properties. Importantly, absorption and emission are red-shifted compared to its classical cationic analog without any cost in terms of thermal stability. In addition to its "cyanine" behavior, this molecule exhibits further redox properties: oxidation and reduction led to the reversible formation of radical species whose absorption is in marked contrast with that of cyanines.