Ligand functionalization as a deactivation pathway in a fac-Ir(ppy)3-mediated radical addition

Knowledge of the kinetic behavior of catalysts under synthetically relevant conditions is vital for the efficient use of compounds that mediate important transformations regardless of their composition or driving force. In particular, these data are of great importance to add perspective to the growing number of applications of photoactive transition metal complexes. Here we present kinetic, synthetic, and spectroscopic evidence of the mechanistic behavior of fac-Ir(ppy)₃ in a visible light-mediated radical addition to 3-methylindole, demonstrating the instability of fac-Ir(ppy)₃ under these conditions. During the reaction, rapid in situ functionalization of the photocatalyst occurs, eventually leading to deactivation. These findings demonstrate a conceivable deactivation process for catalytic single electron reactions in the presence of radicophilic ligands. Attempts to inhibit photocatalyst deactivation through structural modification provide further insight into catalyst selection for a given system of interest.     

Determination of lipid phase transition temperatures in hybrid bilayer membranes

The main gel-to-liquid-crystal (LC) phase transition temperature, T(m), of the lipid monolayer in hybrid bilayer membranes (HBMs) was investigated using vibrational sum frequency spectroscopy (VSFS). In the gel phase, the acyl chains of the lipid molecules assume an ordered, all-trans configuration, whereas in the LC phase, the acyl chains exhibit a significant number of disordered gauche conformers. VSFS has unique sensitivity to the order/disorder transitions in the acyl chains and was used to determine T(m) for a series of saturated phosphatidylcholine lipids on octadecanethiolate self-assembled monolayers (SAMs). The values obtained for T(m) for all lipids studied are significantly higher than for the corresponding lipids in vesicles in solution. Additionally, the transition widths are broader for the lipids in HBMs. The underlying SAM clearly influences the phase behavior of the overlying lipid monolayer.     

Highly enantioselective access to primary propargylamines: 4-piperidinone as a convenient protecting group

[reaction: see text] We report a highly enantioselective, catalytic three-component coupling of aldehydes, alkynes, and 4-piperidone hydrochloride hydrate to afford the corresponding tertiary propargylamines in useful yields. The selective cleavage of the piperidone protecting group using either ammonia/EtOH or a polymer-supported scavenger amine furnishes primary propargylamines.     

Nanometer linear focusing of hard x rays by a multilayer Laue lens

We report on a type of linear zone plate for nanometer-scale focusing of hard x rays, a multilayer Laue lens (MLL), produced by sectioning a multilayer and illuminating it in Laue diffraction geometry. Because of its large optical depth, a MLL spans the diffraction regimes applicable to a thin Fresnel zone plate and a crystal. Coupled wave theory calculations indicate that focusing to 5 nm or smaller with high efficiency should be possible. Partial MLL structures with outermost zone widths as small as 10 nm have been fabricated and tested with 19.5 keV synchrotron radiation. Focal sizes as small as 30 nm with efficiencies up to 44% are measured.     

Coordination and hydrogen bonded network structures of Cu(II) with mixed ligands: a hybrid hydrogen bonded material, an infinite sandwich arrangement, and a 3-D net

Mixed-ligand Cu(II) complexes with deprotonated trimesic acid and phenanthroline-type ligands were synthesised by solvothermal methods to form 2-D infinite hexagonal hydrogen bonded structures with additional trimesic acid (H3tma) molecules. The complex [Cu(phendione)2(H2tma)2].2(H3tma).1.65(CF3CH2OH).2.5(H2O), where phendione = 1,10-phenanthroline-5,6-dione, has hydrogen bonded networks of [Cu(phendione)2(H2tma)2] complexes interspersed with layers of H3tma with a topologically identical hydrogen bonding network. Whereas in [Cu(1,10-phenanthroline)(H2tma)2]2.2(H3tma), a dimeric Cu(II) complex hydrogen bonds directly to additional H3tma molecules to form a three-layered 2-D network resembling an infinite sandwich. The synthesis and structures of simple Cu(II) complexes of the phendione ligand are also reported. One of these, [Cu(phendione)2Br2] shows a particularly polar packing arrangement.     

Synthesis and reactions of some heterobimetallic and multimetallic complexes containing η-arene-ruthenium(II), -osmium(II) and η-Pentamethylcyclopentadienyl-rhodium(III) moieties

Heterobimetallic complexes such as [η-areneMCl(SPPh₂)₂Pt(S₂CNEt₂)] (I, M = Ru, Os) and [η-C₅Me₅RhCl(SPPh₂)₂Pt(S₂CNEt₂)] (II) have been synthesised by reaction of NEt₂H₂[Pt(S₂CNEt₂)(Ph₂PS)₂] with either [M(η-arene)Cl₂]₂ or [Rh(η-C₅Me₅)Cl₂]₂ (2/1) molar ratio). Further reactions of I include facile chloride displacement with a range of neutral ligands L to give [η-areneML(SPPh₂)₂Pt(S₂CNEt₂)⁺ (III) cations and formation of tri- and penta-metallic species on treatment with more [Pt(S₂CNEt₂)(Ph₂PS)₂]^?.