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Intercalation of organic cations in superconducting iron selenide can significantly increase the critical temperature (Tc). We present an electrochemical method using beta-FeSe crystals (Tc ~ 8 K) floating on a mercury cathode to intercalate tetramethylammonium ions (TMA+) quantitatively to obtain bulk samples of (TMA)0.5Fe2Se2 with Tc = 43 K. The layered crystal structure is closely related to the ThCr2Si2-type with disordered TMA+ ions between the FeSe layers. Although the organic ions are not detectable by X-ray diffraction, packing requirements as well as first principle DFT calculations constrain the specified structure. Our synthetic route enables electrochemical intercalations of other organic cations with high yields to greatly optimize the superconducting properties, and to expand this class of high-Tc materials., Comment: 21 pages, 10 Figures, including supplementary information

CaFeO2Cl is a unique exception in the family of the iron oxyhalides. Its crystal structure is not related to the Ruddlesden-Popper phases as known for the other members, but contains layers of edge-sharing FeO2/2O3/3 pyramids without Fe–Cl contacts. The iron atoms form a distorted honeycomb substructure. Magnetization measurements on single crystals show an unexpected weak anisotropy and indicate antiferromagnetic ordering of the iron magnetic moments already at room temperature. 57Fe Mössbauer spectra confirm the trivalent oxidation state of iron and the presence of magnetic order. DFT calculations using the LDA + U approach support a Mott-insulating antiferromagnetic ground state and indicate a Néel-type ordered antiferromagnetic state in the honeycomb layer. The band gap from optical measurements is 1.3 eV and agrees with the red-brown colour as well as with the theoretical calculations.

Intercalation of organic cations in superconducting iron selenide can significantly increase the critical temperature (

This work deals with the spectroscopic properties of single crystalline samples of KTb3F10. Green luminescing KTb3F10 is an efficient UV radiation converter with a quantum yield of about 40% upon UV-A excitation, while it is also an efficient scintillator upon excitation by 20–50 kV X-ray photons. The temperature dependence of the integral photoluminescence as well as the decay time of KTb3F10 monitored for the Tb3+ emission show that the internal quantum yield between 100 and 800 K is almost constant, while the external quantum yield is modulated, likely due to a change in reabsorption at elevated temperatures. In contrast, the low temperature range between 3 and 63 K reveals a change of the local Tb3+ environment in KTb3F10, which is indicated by an anomaly in the heat capacity and by a strong change of the decay time as well as by a distinct shift of the photoluminescence spectra at low temperatures. In addition, temperature dependent magnetic susceptibility measurements and a structure refinement based on single crystal X-ray diffraction data were performed.

A series of bis(pyrazolyl)methane copper complexes were found to catalyze a fast palladium-free Sonogashira coupling reaction of several iodoarenes with terminal alkynes such as phenylacetylene, propargyl benzyl ether, and (tert-butyl-dimethyl)silylacetylene. These reactions proceed with CuCl2·2H2O (10 mol-%) under aerobic conditions and the corresponding chelate ligand (10 mol-%), with its tailored facial coordination mode, is crucial for the success of the reaction. The coupling can also be carried out in water with liquid aryl halides and a phase-transfer catalyst.