Mechanistic Insight into the Chemiluminescent Decomposition of Cypridina Dioxetanone and the Chemiluminescent, Fluorescent Properties of the Light Emitter of Cypridina Bioluminescence.

Cypridina bioluminescence has been increasingly used in bioimaging, bioanalysis, and biomedicine, due to high quantum yield and high signal-to-noise ratio. However, there is still no consensus regarding different aspects of the chemiluminescent mechanism of this system, which impairs the development of new applications. Herein, we have used a theoretical DFT and TD-DFT approach to (i) determine the identity of the dioxetanone species responsible for efficient chemiexcitation and (ii) identify the bioluminescent emitter and determine if light-emission occurs from the fluorescent or chemiluminescent state. Our results demonstrate that upon oxygenation of the imidazopyrazinone scaffold, a dioxetanone with a neutral amide group and a cationic guanidinopropyl group is formed. This species is efficiently chemiexcited (with no obvious charge transfer step) to the corresponding oxyluciferin with a neutral amide and cationic guanidinopropyl groups. After the "dark" chemiluminescent state, this oxyluciferin species is converted into a bright blue-emitting fluorescent state.

Controllable Synthesis and Characterization of AuPd Nanowire Networks with High Electrocatalytic Performance.

A simple and efficient method is proposed for the synthesis of bimetallic AuPd nanowire networks (NWs) with tunable compositions by using KBr as a structure-directing agent and NaBH4 as a reducing agent. TEM, XRD and XPS results show that the AuPd NWs have a unique one-dimensional network structure. Electrochemical tests indicate that the AuPd NWs catalysts have excellent electrocatalytic activity and durability for methanol oxidation due to the special one-dimensional nanostructure and many structural defects at the junction. The Au1Pd1 NWs show better catalytic activity, which is 2.03 times higher than that of the commercial Pd/C catalyst.

Bottom-Up Construction of Active Sites in a Cu-N4-C Catalyst for Highly Efficient Oxygen Reduction Reaction.

Bottom-up construction of efficient active sites in transition metal-nitrogen-carbon (M-N-C) catalysts for oxygen reduction reaction (ORR) from single molecular building blocks remains one of the most difficult challenges. Herein, we report a bottom-up approach to produce a highly active Cu-N4-C catalyst with well-defined Cu-N4 coordination sites derived from a small molecular copper complex containing Cu-N4 moieties. The Cu-N4 moieties were found to be covalently integrated into graphene sheets to create the Cu-N4 active sites for ORR. Furthermore, the activity was boosted by tuning the structure of active sites. We find that the high ORR activity of the Cu-N4-C catalyst is related to the Cu-N4 center linked to edges of the graphene sheets, where the electronic structure of the Cu center has the right symmetry for the degenerate π* orbital of the O2 molecule. These findings point out the direction for the synthesis of the M-N-C catalysts at the molecular level.

Pd@C core-shell nanoparticles on carbon nanotubes as highly stable and selective catalysts for hydrogenation of acetylene to ethylene.

Developing highly selective and stable catalysts for acetylene hydrogenation is an imperative task in the chemical industry. Herein, core-shell Pd@carbon nanoparticles supported on carbon nanotubes (Pd@C/CNTs) were synthesized. During the hydrogenation of acetylene, the selectivity of Pd@C/CNTs to ethylene was distinctly improved. Moreover, Pd@C/CNTs showed excellent stability during the hydrogenation reaction.

A Computational Investigation of the Equilibrium Constants for the Fluorescent and Chemiluminescent States of Coelenteramide.

In spite of recent advances in understanding the mechanism of coelenterate bioluminescence, there is no consensus about which coelenteramide specie and/or state are the light emitter. In this study, a systematic investigation of the geometries and spectra of all possible light emitters has been performed at the TD ωB97XD/6-31+G(d) level of theory, including various fluorescent and chemiluminescent states in vacuum, in a hydrophobic environment and in aqueous solution. To deduce the most probable form of the fluorescent and chemiluminescent coelenteramide emitter, the equilibrium constants for the fluorescent and chemiluminescent states connecting the various species have been calculated. ωB97XD gives a qualitatively good description of fluorescent and chemiluminescent structures. Coelenteramide is formed in a "dark" chemiluminescent state and must evolve to a bright fluorescent state. Moreover, the photoacidity of the phenol group is significantly higher in the fluorescent state than in the chemiluminescent state, which allows the formation of phenolate coelenteramide and clarifies its role as the bioluminescent emitter.

Catechol degradation on hematite/silica-gas interface as affected by gas composition and the formation of environmentally persistent free radicals.

Environmentally persistent free radicals (EPFRs) formed on a solid particle surface have received increasing attention because of their toxic effects. However, organic chemical fate regulated by EPFRs has rarely been investigated, and this information may provide the missing link in understanding their environmental behavior. Previous studies have suggested that the reduction of transition metals is involved in EPFRs formation. We thus hypothesize that an oxidative environment may inhibit EPFRs formation in particle-gas interface, which will consequently release free radicals and accelerate organic chemical degradation. Our result indicates that a 1% hematite coating on a silica surface inhibited catechol degradation in N2, especially at low catechol loadings on solid particles (SCT). However, under an O2 environment, catechol degradation decreased when SCT was <1 µg/mg but increased when SCT was >1 µg/mg. Stable organic free radicals were observed in the N2 system with g factors in the 2.0035-2.0050 range, suggesting the dominance of oxygen-centered free radicals. The introduction of O2 into the catechol degradation system substantially decreased the free radical signals and decreased the Fe(II) content. These results were observed in both dark and light irradiation systems, indicating the ubiquitous presence of EPFRs in regulating the fate of organic chemicals.

Diaqua-bis-(4,4'-bipyridine-κN)bis-(2,4,5-trifluoro-3-hy-droxy-benzoato-κO)manganese(II).

In the title compound, [Mn(C(7)H(2)F(3)O(3))(2)(C(10)H(8)N(2))(2)(H(2)O)(2)], the Mn(II) ion, situated on a centre of inversion, has a distorted octa-hedral coordination geometry and is coordinated by two N atoms from two 4,4'-bipyridine ligands, two O atoms from two 2,4,5-trifluoro-3-hy-droxy-benzoate ligands and two water mol-ecules. Inter-molecular O-H⋯N hydrogen bonds link the mol-ecules into a chain along the a axis. Inter-actions between neighboring chains occur through O-H⋯O hydrogen bonds, which link the chains into a two-dimensional supra-molecular network parallel to the ac plane. In addition, O-H⋯O hydrogen bonds between the water mol-ecules and carboxyl-ate groups also exist in the the crystal structure.