ππ production by ee annihilation in the ϱ energy range with the Orsay storage ring

A large solid angle detector has been used to observe two body events produced by electron-positron collisions in the Orsay storage ring. From the π⁺π⁻ excitation curve in the ? region we have deduced the amplitude and the phase of the ω-? interference, and the ? resonance paramaters: M_? = (775.4±7.3) MeV, Γ_? = (149.6 ± 23.2) MeV, √B(ω→π⁺π⁻) = 0.19 ± 0.05, φ = (85.7 ± 15.3)⁰, σ(e⁺e⁻→?) = (1.00 ± 0.13) μb at S = M_?², B(?→e⁺e⁻ = (4.1 ± 0.5) × 10⁻⁵, Γ(?→e⁺e⁻) = (6.1 ± 0.7) keV, (g_?²/4π) = 2.26 ± 0.25, (g_?ππ²/4π) = 2.84 ± 0.50.     

A Flexible Copper(I)‐Complexed [4]Rotaxane Containing Two Face‐to‐Face Porphyrinic Plates that Behaves as a Distensible Receptor

A new cyclic [4]rotaxane composed of two flexible bis‐macrocycles and two rigid axles is described. Each bis‐macrocycle consists of two rings attached to antipodal meso positions of a central Zn porphyrin through single C? C bonds. Each ring incorporates a 2,9‐diphenyl‐1,10‐phenanthroline chelation site. The axles contain two coplanar bidentate sites derived from the 2,2′‐bipyridine motif. The building blocks were assembled by using a one‐pot threading‐and‐stoppering reaction, which afforded the [4]rotaxane in 50 % yield. The “gathering‐and‐threading” effect of copper(I) was utilised in the formation of a [4]pseudorotaxane, which was immediately converted to the corresponding [4]rotaxane by a quadruple CuAAC stoppering reaction. The rotaxane contains two face‐to‐face zinc porphyrins, which allowed the coordination of ditopic guest substrates. The rotaxane host showed remarkable flexibility and was able to adjust its conformation to the guest size. It can be distended and accommodate rod‐like guests of 2.6 to 15.8 Å in length.     

Chiral spiro Cu(I) complexes. Supramolecular stereocontrol and isomerisation dynamics by the use of TRISPHAT anions

Association of enantiopure TRISPHAT anion (1) with chiral spiro [Cu(LL')2] complexes (LL' = 2-R-phen, 2, 6-R-bpy, 3, and 2-iminopyridine, 4) leads to an efficient NMR enantiodifferentiation. Variable temperature 1H NMR spectroscopy has been used to determine the isomerisation kinetics of these pseudo-tetrahedral complexes and to evaluate their configurational stability; the latter depending on the structure of the diimine ligands. In the case of the 2-anthracenyl-phen derivative, a decent level of supramolecular stereocontrol was noted (d.e. up to 45%); the configuration of the complex being determined by electronic circular dichroism (ECD).     

Butyronitrile-based electrolyte for dye-sensitized solar cells

We elaborated a new electrolyte composition, based on butyronitrile solvent, that exhibits low volatility for use in dye-sensitized solar cells. The strong point of this new class of electrolyte is that it combines high efficiency and excellent stability properties, while having all the physical characteristics needed to pass the IEC 61646 stability test protocol. In this work, we also reveal a successful approach to control, in a sub-Nernstian way, the energetics of the distribution of the trap states without harming cell stability by means of incorporating NaI in the electrolyte, which shows good compatibility with butyronitrile. These excellent features, in conjunction with the recently developed thiophene-based C106 sensitizer, have enabled us to achieve a champion cell exhibiting 10.0% and even 10.2% power conversion efficiency (PCE) under 100 and 51.2 mW·cm(-2) incident solar radiation intensity, respectively. We reached >95% retention of PCE while displaying as high as 9.1% PCE after 1000 h of 100 mW·cm(-2) light-soaking exposure at 60 °C.     

Porphyrinic dyads and triads assembled around iridium(III) bis-terpyridine: photoinduced electron transfer processes

Multicomponent arrays based on a central iridium(III) bis-terpyridine complex (Ir) used as assembling metal and free-base, zinc(II) or gold(III) tetraaryl-porphyrins (PH(2), PZn, PAu) have been designed to generate intramolecular photoinduced charge separation. The rigid dyads PH(2)-Ir, PZn-Ir, PAu-Ir, and the rigid and linear triads PH(2)-Ir-PAu, PZn-Ir-PAu, as well as the individual components Ir, PH(2), PZn, PAu have been synthesized and characterized by various techniques including electrochemistry. Their photophysical properties either in acetonitrile or in dichloromethane and toluene have been determined by steady-state and time-resolved methods. In acetonitrile, excitation of the triad PH(2)-Ir-PAu leads to a charge separation with an efficiency of 0.5 and a resulting charge-separated (CS) state with a lifetime of 3.5 ns. A low-lying triplet localized on PH(2) and the presence of the heavy Ir(III) ion offer the CS state an alternative deactivation path through the triplet state. The behavior of the triad PZn-Ir-PAu in dichloromethane is rather different from that of PH(2)-Ir-PAu in acetonitrile since the primary electron transfer to yield PZn(+)()-Ir(-)-PAu is not followed by a secondary electron transfer. In this solvent, both unfavorable thermodynamic and electronic parameters contribute to the inefficiency of the second electron-transfer reaction. In contrast, in toluene solutions, the triad PZn-Ir-PAu attains a CS state with a unitary yield and a lifetime of 450 ns. These differences can be understood in terms of ground-state charge-transfer interactions as well as different stabilization of the intermediate and final CS states by solvent.     

Properties of the low-lying levels in the transitional Ir and Au nuclei

We try to determine to what extent an “axial prolate rotor +1 or 2 quasiparticle model” succeeds in describing the transitional odd and odd-odd Ir and Au nuclei. The relative location of the excited states, as well as the properties of the ground and isomeric states, particularly the magnetic and spectroscopic quadrupole moments, is compared to the predictions of the model.