Man‐Ho So

Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43-100%) and product yields (66-99%) (19 examples). Oxidation of N-substituted 1,2,3,4-tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83-93%) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o-phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N-benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O2" can be scaled to the gram scale, and 8.9 g (84 % isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4-tetrahydroisoquinoline in a one-pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed.

The oxidative dissolution of silver nanoparticles (AgNPs) plays an important role in the synthesis of well-defined nanostructured materials, and may be responsible for their activities in biological systems. In this study, we use stopped-flow spectrophotometry to investigate the kinetics and mechanism of the oxidative dissolution of AgNPs by H(2)O(2) in quasi-physiological conditions. Our results show that the reaction is first order with respect to both [Ag(0)] and [H(2)O(2)], and parallel pathways that involve the oxidation of H(2)O(2) and HO(2)(-) are proposed. The order of the reaction is independent of the size of the AgNPs (approximately 5-20 nm). The rate of dissolution increases with increasing pH from 6.0 to 8.5. At 298 K and I=0.1 M, the value of k(b) is five orders of magnitude higher than that of k(a) (where k(a) and k(b) are the rate constants for the oxidative dissolution of AgNPs by H(2)O(2) and HO(2)(-), respectively). In addition, the effects of surface coating and the presence of halide ions on the dissolution rates are investigated. A possible mechanism for the oxidative dissolution of AgNPs by H(2)O(2) is proposed. We further demonstrate that the toxicities of AgNPs in both bacteria and mammalian cells are enhanced in the presence of H(2)O(2), thereby highlighting the biological relevance of investigating the oxidative dissolution of AgNPs.

Organometallic nanowires with luminescent and current-modulating properties were self-assembled from cyclometalated/terpyridyl platinum(II) complexes with auxiliary arylisocyanide/arylacetylide ligands and incorporated into a compact organic light-emitting field-effect transistor (see picture) by solution-processable protocols. The nanowires exhibit both electron and hole mobilities of 0.1 cm2 V−1 s−1. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A series of gold(I) complexes with N-heterocyclic carbene (NHC) and acetylide ligands, namely [Au(NHC(1))(C≡CAr)] (NHC(1)=1-(9-anthracenylmethyl)-3-(n)-butylimidazol-2-ylidene; 1b-1g), [Au(NHC(2))(C≡CAr)] (NHC(2)=1,3-diethylimidazol-2-ylidene; 2b-2f) and [Au(C≡NAr)(2)](+) (C≡NAr=arylisocyanide; 3a-3f) have been synthesized. At room temperature, most of these gold(I) complexes are emissive in the solid state and in solutions with lifetimes in the nanosecond to submicrosecond regime. The emissions of complexes 1b-1g in solutions are assigned to (1)π-π* excited states of the NHC ligand, while that of 2b-2f and 3a-3f are phosphorescent in nature. The intriguing solvatochromism of complex 3a was also investigated. Complexes 1b, 1d, 3a, and 3e aggregate into crystalline nanowires in freshly prepared THF/water dispersions. The X-ray crystallographic data reveal that 1b and 1d possess intermolecular π-π and C-H···π interactions; while 3a was found to display intermolecular gold(I)···π interactions.