Direct Superacid-Promoted Difluoroethylation of Aromatics

Under superacid conditions, aromatic amines are directly and regioselectively 1,1-difluoroethylated. Low temperature in situ NMR studies confirmed the presence of benzylic α-fluoronium and α-chloronium ions as key intermediates in the reaction. This method has a wide substrate scope and can be applied to the late-stage functionalization of natural alkaloids and active pharmaceutical ingredients.     

Synthesis and Photophysical Properties of 1,1,4,4-Tetracyanobutadienes Derived from Ynamides Bearing Fluorophores**

1,1,4,4-Tetracyanobutadienes (TCBDs) bearing a large diversity of fluorophores were prepared following a multi-step synthesis. In a crucial last step, all compounds were obtained from the corresponding ynamides, which were particularly suitable for the formation of the TCBDs in the presence of tetracyanoethylene via a [2+2] cycloaddition/retroelectrocyclization step (CA-RE). Several fluorenyl derivatives in addition to phenanthrenyl and terphenyl ones provided ynamide-based TCBDs affording remarkable emission properties covering a large range of wavelengths. Those compounds emit both in solid state and in solution from the visible region to the NIR range, depending on the molecular structures. Quantum yields in cyclohexane reached unforeseen values for such derivatives, up to 7.8 %. A huge sensitivity to the environment of the TCBDs has also been unraveled for most of the compounds since we observed a dramatic fall of the quantum yields when changing the solvent from cyclohexane to toluene, while they are almost non-emissive in dichloromethane.     

Mimicking Photosystem I with a Transmembrane Light Harvester and Energy Transfer-Induced Photoreduction in Phospholipid Bilayers

Photosystem I (PS I) is a transmembrane protein that assembles perpendicular to the membrane, and performs light harvesting, energy transfer, and electron transfer to a final, water-soluble electron acceptor. We present here a supramolecular model of it formed by a bicationic oligofluorene 1²⁺ bound to the bisanionic photoredox catalyst eosin Y (EY²⁻) in phospholipid bilayers. According to confocal microscopy, molecular modeling, and time dependent density functional theory calculations, 1²⁺ prefers to align perpendicularly to the lipid bilayer. In presence of EY²⁻, a strong complex is formed (K_a=2.1±0.1×10⁶ m ⁻¹), which upon excitation of 1²⁺ leads to efficient energy transfer to EY²⁻. Follow-up electron transfer from the excited state of EY²⁻ to the water-soluble electron donor EDTA was shown via UV–Vis absorption spectroscopy. Overall, controlled self-assembly and photochemistry within the membrane provides an unprecedented yet simple synthetic functional mimic of PS I.     

Engineering sticky superomniphobic surfaces on transparent and flexible PDMS substrate

Following the achievement of superhydrophobicity which prevents water adhesion on a surface, superomniphobicity extends this high repellency property to a wide range of liquids, including oils, solvents, and other low surface energy liquids. Recent theoretical approaches have yield to specific microstructures design criterion to achieve such surfaces, leading to superomniphobic structured silicon substrate. To transfer this technology on a flexible substrate, we use a polydimethylsiloxane (PDMS) molding process followed by surface chemical modification. It results in so-called sticky superomniphobic surfaces, exhibiting large apparent contact angles (>150°) along with large contact angle hysteresis (>10°). We then focus on the modified Cassie equation, considering the 1D aspect of wetting, to explain the behavior of droplets on these surfaces and compare experimental data to previous works to confirm the validity of this model.     

Induction of a Four‐Way Junction Structure in the DNA Palindromic Hexanucleotide 5′‐d(CGTACG)‐3′ by a Mononuclear Platinum Complex

Four‐way junctions (4WJs) are supramolecular DNA assemblies comprising four interacting DNA strands that in biology are involved in DNA‐damage repair. In this study, a new mononuclear platinum(II) complex 1 was prepared that is capable of driving the crystallization of the DNA oligomer 5′‐d(CGTACG)‐3′ specifically into a 4WJ‐like motif. In the crystal structure of the 1 –CGTACG adduct, the distorted‐square‐planar platinum complex binds to the core of the 4WJ‐like motif through π–π stacking and hydrogen bonding, without forming any platinum–nitrogen coordination bonds. Our observations suggest that the specific molecular properties of the metal complex are crucially responsible for triggering the selective assembly of this peculiar DNA superstructure.     

Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal‐Mediated Peroxynitrite Decomposition

We report the formation of a new copper peroxynitrite ( PN ) complex [Cu^II(TMG₃tren)(κ¹‐OONO)]⁺ ( PN1 ) from the reaction of [Cu^II(TMG₃tren)(O₂^.?)]⁺ ( 1 ) with NO^._(g) at ?125 °C. The first resonance Raman spectroscopic characterization of such a metal‐bound PN moiety supports a cis κ¹‐(^?OONO) geometry. PN1 transforms thermally into an isomeric form ( PN2 ) with κ²‐O,O′‐(^?OONO) coordination, which undergoes O?O bond homolysis to generate a putative cupryl (LCu^II?O^.) intermediate and NO₂^.. These transient species do not recombine to give a nitrato (NO₃^?) product but instead proceed to effect oxidative chemistry and formation of a Cu^II–nitrito (NO₂^?) complex ( 2 ).     

Energy balance measurements on a nanosecond CO2 laser created plasma

Interaction of nanosecond CO₂ laser radiation with a solid deuterium target has been investigated with incident laser fluxes up to several times 10¹²W/cm². Reflection, X-ray and ion measurements were performed at different angles in the relevant half-space around the target. The energy balance deduced from reflection and ion time-of-flight measurements led to a total integrated reflectivity of 60 to 80%. Fast D⁺ ions with kinetic energies as high as 40 keV were detected and identified. Hard X-rays were observed in the range of 1 to 10 keV. A discussion of these results is presented.     

Obtaining the apex of the unitarity triangle from B-->piK decays

We present a method of obtaining the apex of the unitarity triangle from measurements of B-->piK decay rates alone. Electroweak penguin amplitudes are included, and are related to tree operators. Discrete ambiguities are removed by comparing solutions with independent experimental data. The theoretical uncertainty in this method is about 10%.