Yuhui Yang

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla-aromatics.

Antiaromatic species are substantially less thermodynamically stable than aromatic moieties. Herein, we report the stabilization of two classical antiaromatic frameworks, cyclobutadiene and pentalene, by introducing one metal fragment through the first [2+2] cycloaddition reaction of a late-transition-metal carbyne with alkynes. Experimental observations and theoretical calculations reveal that the metal fragment decreases the antiaromaticity in cyclobutadiene and pentalene simultaneously, leading to air- and moisture-stable products. These molecules show broad absorption from the UV to the near-IR region, resulting in photoacoustic and photothermal effects for metalla-aromatic compounds for the first time. These results will encourage further efforts into the exploration of organometallic compounds for photoacoustic-imaging-guided photothermal therapy.

Five-membered cyclic metal carbyne: synthesis of osmapentalynes by the reactions of osmapentalene with allene, alkyne, and alkene.

The synthesis of small cyclic metal carbynes is challenging due to the large angle strain associated with the highly distorted nonlinear triple bonds. Herein, we report a general route for the synthesis of five-membered cyclic metal carbyne complexes, osmapentalynes, by the reactions of an osmapentalene derivative with allene, alkyne, and alkene. Experimental observations and theoretical calculations document the aromaticity in the fused five-membered rings of osmapentalynes. The realization of transforming osmapentalene to osmapentalyne through this general route would not only allow further exploration of metallapentalyne chemistry but also show promising applications of this novel aromatic system with broad absorption band and high molar absorption coefficient.

Reactions of Isocyanides with Metal Carbyne Complexes: Isolation and Characterization of Metallacyclopropenimine Intermediates

η2-Iminoketenyl species have often been postulated as the intermediates in nucleophile-induced carbyne-isocyanide C-C coupling processes. However, such species are elusive. Here we report direct formation of η2-iminoketenyl complexes from reactions of metallapentalyne with isocyanides. Our studies show that steric effects of N-substituents of the isocyanides play an important role in the stability of the three-membered metallacycles of the η2-iminoketenyl complexes. Sterically bulky isocyanides, such as tert-butyl or 1-adamantyl isocyanides, inhibit bending at the isocyanide nitrogen atoms, a requirement for formation of η2-iminoketenyl structures. Reactions of metallapentalyne with excess isocyanide allow the metal-bridged metallaindene derivativesto be isolated as a result of the isocyanide insertion into the M-Cα σ bond of metallapentalyne.

CCCCC pentadentate chelates with planar Möbius aromaticity and unique properties

Planar Möbius aromatic metallacycles show NIR absorption spectrum and the highest carbon coordination number for a metal atom. The coordinating atoms in polydentate chelates are primarily heteroatoms. We present the first examples of pentadentate chelates with all binding atoms of the chelating agent being carbon atoms, denoted as CCCCC chelates. Having up to five metal-carbon bonds in the equatorial plane has not been previously observed in transition metal chemistry. Density functional theory calculations showed that the planar metallacycle has extended Craig-Möbius aromaticity arising from 12-center–12-electron dπ-pπ π-conjugation. These planar chelates have broad absorption in the ultraviolet-visible–near-infrared region and, thus, notable photothermal performance upon irradiation by an 808-nm laser, indicating that these chelates have potential applications in photothermal therapy. The combination of facile synthesis, high stability, and broad absorption of these complexes could make the polydentate carbon chain a novel building block in coordination chemistry.

Performance and characterization of lithium-manganese-oxide cathode material with large tunnel structure for lithium batteries

Abstract The synthesis, structure characterization and electrochemical performance of novel todorokite electrode materials (tunnel size: 3×3) for lithium batteries have been studied in this paper. It is shown by means of XRD that synthesized materials (e.g., Mg 2+ -containing sample) have todorokite structure. It is also found that the reversibility of the Li + insertion process into the todorokite materials decreased after acid treatment due to removal of Mg 2+ from the tunnel and the breakdown of the tunnel structure during the following intercalation/deintercalation cycles. The electrochemical impedance spectra (EIS) for todorokite electrode materials are measured and simulated. It was measured that the apparent diffusion coefficient ( D Li+ ) of todorokite material is at a level between 10 −7 and 10 −10 cm 2 /s by use of potential-step electrochemical spectroscopy.

In-situ and ex-situ characterization of surface oxide films on AB5-type metal hydride electrodes

Abstract The surface oxide films on AB 5 -type metal hydride electrodes have been investigated by means of in-situ and ex-situ techniques such as in-situ laser scanning photoelectrochemical microscopy (PEM), ex-situ scanning tunneling microscopy (STM) and in-situ confocal Raman spectroscopy. The results indicated that the growth of surface oxide films can be monitored by using in-situ photoelectrochemical methods. Both laser-scanning photoelectrochemical microscopic and confocal Raman microscopic results showed that crack sites on the electrode surface are more feasible to be oxidized than other smooth sites under electrochemical conditions. In addition, the primary surface oxide layer on fresh metal hydride electrode was found to be composite metal oxides with nickel oxide as its main component.

Distribution and laser-induced behavior of lead monooxide on lead electrodes in acid solution

Abstract The distribution and laser-induced behaviour of PbO on lead electrodes have been investigated using photoelectrochemical microscopic (PEM) and cyclic voltammetric techniques. A linear relationship between the potential of the reduction peak for lead monooxide and the pre-oxidation time of the electrodes was obtained at low potential-sweep rates. This result implies that the changes of pH within the inner anodic films could be estimated using the electrochemical method. Some interesting photocurrent characteristics of “laser-induced” oxide “islands” have been observed. In addition, a linear growth mode of PbO has been found at an early stage of growth of the anodic films using a “line-scan” method in the PEM technique.

Isolation of an Eleven‐Atom Polydentate Carbon‐Chain Chelate Obtained by Cycloaddition of a Cyclic Osmium Carbyne with an Alkyne

Carbon ligands have long played an important role in organometallic chemistry. However, previous examples of all-carbon chelating ligands are limited. Herein, we present a novel complex with an eleven-atom carbon chain as a polydentate chelating ligand. This species was formed by the [2+2+2] cycloaddition reaction of two equivalents of an alkyne with an osmapentalyne that contains the smallest carbyne bond angle (127.9°) ever observed. Density functional calculations revealed that electron-donating groups play a key role in the stabilization of this polydentate carbon-chain chelate. This process is also the first [2+2+2] cycloaddition reaction of an alkyne with a late-transition-metal carbyne complex. This study not only enriches the chemistry of polydentate carbon-chain chelates, but also deepens our understanding of the chelating ability of carbon ligands.