IRMPD Spectroscopy of a Protonated,Phosphorylated Dipeptide

The protonated, phosphorylated dipeptide [GpY+H]⁺ is characterized by mid‐infrared multiple‐photon dissociation (IRMPD) spectroscopy and quantum‐chemical calculations. The ions are generated in an external electrospray source and analyzed in a Fourier transform ion cyclotron resonance mass spectrometer, and their fragmentation is induced by resonant absorption of multiple photons emitted by a tunable free‐electron laser. The IRMPD spectra are recorded in the 900–1730 cm^?1 range and compared to the absorption spectra computed for the lowest energy structures. A detailed calibration of computational levels, including B3LYP‐D and coupled cluster, is carried out to obtain reliable relative energies of the low‐energy conformers. It turns out that a single structure can be invoked to assign the IRMPD spectrum. Protonation at the N terminus leads to the formation of a strong ionic hydrogen bond with the phosphate P?O group in all low‐energy structures. This leads to a P?O stretching frequency for [GpY+H]⁺ that is closer to that of [pS+H]⁺ than to that of [pY+H]⁺ and thus demonstrates the sensitivity of this mode to the phosphate environment. The COP phosphate ester stretching mode is confirmed to be an intrinsic diagnostic for identification of which type of amino acid is phosphorylated.     

Generation of phosphorus-centered radicals via homolytic substitution at sulfur

A novel radical domino process relying on the homolytic cleavage of P-S bonds allows the preparation of phosphorus-containing molecules through addition of P-centered radicals onto olefins. The key step of this reaction is a homolytic substitution on a sulfur atom. The scope of the reaction is broad. Diaminophosphonyl radicals whose reactivity was unknown react smoothly with olefins. Use of tin hydride can be avoided. A radical thiophosphinoylation of triple bonds has been uncovered. [reaction: see text]     

Fullerene Derivatives Functionalized with Diethylamino‐Substituted Conjugated Oligomers: Synthesis and Photoinduced Electron Transfer

Diethylamino‐substituted oligophenylenevinylene (OPV) building blocks have been prepared and used for the synthesis of two [60]fullerene–OPV dyads, F‐D1 and F‐D2 , which exhibit different conjugation length of the OPV fragments. The electrochemical properties of these acceptor–donor dyads have been studied by cyclic voltammetry. The first reduction is always assigned to the fullerene moiety and the first oxidation centered on the diethylaniline groups of the OPV rods, thus making these systems suitable candidates for photoinduced electron transfer. Both the OPV and the fullerene‐centered fluorescence bands are quenched in toluene and benzonitrile, which suggests the occurrence of photoinduced electron transfer from the amino‐substituted OPVs to the carbon sphere in the dyads in both solvents. By means of bimolecular quenching experiments, transient absorption spectral fingerprints of the radical cationic species are detected in the visible (670 nm) and near‐IR (1300–1500 nm) regions, along with the much weaker fullerene anion band at λ_max=1030 nm. Definitive evidence for photoinduced electron transfer in F‐D1 and F‐D2 comes from transient absorption measurements. A charge‐separated state is formed within 100 ps and decays in less than 5 ns.     

Synthesis of functionalized 2-arylpyridines from 2-halopyridines and various aryl halides via a nickel catalysis

An efficient nickel-catalyzed method devoted to the direct formation of functionalized 2-arylpyridines is described avoiding the prior preparation of organometallic species. Various functionalized 2-arylpyridines are obtained in moderate to excellent yields by a one-step chemical procedure from corresponding halides. The NiBr₂(2,2′-bipyridine) complex appears to be an extremely suitable catalyst for the activation in the presence of manganese dust of aromatic halides and pyridyl halides functionalized by reactive groups. The versatility of this original process represents a simple alternative to most known methods using organometallic reagents.