Alkoxycarbonyl Groups in Metalloesters Showing Oxocarbenium-like Structure and Alkylating Reactivity.

In contrast to the well-documented acylating reactivity, the alkylating reactivity of the alkoxycarbonyl group, as signified by its oxocarbenium-like resonance structure, remains almost unexplored. Herein, the first series of Co/Ni dinuclear metalloesters exhibiting the novel oxocarbenium-like alkoxycarbonyl groups were synthesized and characterized. In these deformed alkoxycarbonyl groups, the Ccarbonyl-Oalkoxyl bonds were contracted to 1.177(11)~1.191(9) Šwith the elongations of the Ccarbonyl=Ocarbonyl bonds to 1.368(13)~1.441(9) Å. Meanwhile, the O-Calkyl bonds were also elongated to 1.522(11) ~1.607(15) Å, and were by far the longest O-Calkyl bonds reported for alkoxycarbonyl groups. As triggered by the long O-Calkyl distances, the alkylating reactivity of the oxocarbenium-like methoxycarbonyl group towards a series of C/N/O-nucleophiles via the rare BAL2 mechanism at ambient conditions was examined. Furthermore, the homo-etherifications of alcohols mediated by the Co/Ni dinuclear metalloesters were investigated. The yields followed the trend ethanol≫n-propanol≫n-butanol ≈n-pentanol, that closely related to the structure features of the alkoxycarbonyl groups in corresponding metalloesters: while the ethoxycarbonyl group showed the reactive oxocarbenium-like framework, the n-propoxycarbonyl group displayed the dioxocarbenium-like skeleton with a shorter O-Calkyl bond; In comparison, the classical frameworks with unactivated alkyl moieties were observed for n-butoxycarbonyl and n-pentoxycarbonyl groups.

A Library of Rare Earth Oxide Ultrathin Nanowires with Polymer-Like Behaviors.

Ultrathin nanowires (NWs) have always attracted the attention of researchers due to their unique properties, but their facile synthesis is still a great challenge. Herein we developed a general method for the synthesis of rare earth (RE) oxide ultrathin NWs at atmospheric pressure and low temperature (50 °C). The formation mechanism of ultrathin NWs lies in two aspects: thermodynamic advantage of one dimensional (1D) growth at low temperature, and supplement of effective monomers. As an extension, fifteen kinds of RE oxide ultrathin NWs were synthesized through this strategy, and they all exhibited polymer-like behaviors. Meanwhile, the high viscosity, organic gel, wet- and electro-spinning of Ce-Mo-O NWs were studied in detail, demonstrating the similarity of ultrathin inorganic NWs to polymers. In addition, the Ce-Mo-O ultrathin NWs were used as photocatalysts for toluene oxidation and showed excellent performance with toluene conversion ratio of 83.8 %, suggesting their potential application in organic photocatalysis.

Direct synthesis of oxalic acid via oxidative CO coupling mediated by a dinuclear hydroxycarbonylcobalt(III) complex.

Oxidative coupling of CO is a straightforward and economic benign synthetic route for value-added α-diketone moiety containing C2 or higher carbon compounds in both laboratory and industry, but is still undeveloped to date. In this work, a rare coplanar dinuclear hydroxycarbonylcobalt(III) complex, bearing a Schiff-base macrocyclic equatorial ligand and a µ-κ1(O):κ1(O')-acetate bridging axial ligand, is synthesized and characterized. The Co(III)-COOH bonds in this complex can be feasibly photocleaved, leading to the formation of oxalic acid. Moreover, the light-promoted catalytic direct production of oxalic acid from CO and H2O using O2 as the oxidant with good selectivity (> 95%) and atom economy at ambient temperature and gas pressure based on this dicobalt(III) complex have been achieved, with a turnover number of 38.5. The 13C-labelling and 18O-labelling experiments confirm that CO and H2O act as the sources of the -COOH groups in the dinuclear hydroxycarbonylcobalt(III) complex and the oxalic acid product.

Optical Properties of a CsMnBr3 Single Crystal.

Lead-free perovskite materials with good stability are promising for various applications. In order to explore their application in optoelectronic devices, it is essential to investigate their fundamental optical properties. In this work, we have synthesized a CsMnBr3 single crystal (SC) with red emission at ∼621 nm and studied their optical properties. Through the measurement of temperature-dependent photoluminescence (PL) spectra, it is found that a phase transition occurs at approximately 100 K in the SC, which is absent in the CsMnBr3 nanocrystals (NCs). Furthermore, the SC exhibits stronger electron and longitudinal optical phonon coupling strength than that of the NCs at low temperatures. In addition, under the resonant excitation at 600 nm, the SC possesses strong saturable absorption property, with a modulation depth of ∼27%. Interestingly, the SC also exhibits a large two-photon absorption coefficient of ∼0.035 cm GW-1 at 800 nm and an excellent optical limiting behavior. The experimental results indicate that the CsMnBr3 SC is a class of excellent environmentally friendly optoelectronic materials.