Over the past decade, photoredox catalysis has harnessed light energy to accelerate bond-forming reactions. We postulated that a complementary method for the redox-activation of small organic molecules in response to applied mechanical energy could be developed through the piezoelectric effect. Here, we report that agitation of piezoelectric materials via ball milling reduces aryl diazonium salts. This mechanoredox system can be applied to arylation and borylation reactions under mechanochemical conditions.

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BiCh2-based compounds (Ch: S, Se) are a new series of layered superconductors, and the mechanisms for the emergence of superconductivity in these materials have not yet been elucidated. In this study, we investigate the relationship between crystal structure and superconducting properties of the BiCh2-based superconductor family, specifically, optimally doped Ce1−xNdxO0.5F0.5BiS2 and LaO0.5F0.5Bi(S1−ySey)2. We use powder synchrotron X-ray diffraction to determine the crystal structures. We show that the structure parameter essential for the emergence of bulk superconductivity in both systems is the in-plane chemical pressure, rather than Bi-Ch bond lengths or in-plane Ch-Bi-Ch bond angle. Furthermore, we show that the superconducting transition temperature for all REO0.5F0.5BiCh2 superconductors can be determined from the in-plane chemical pressure.

F-substituted NdOBiS 2 superconducting single crystals were grown using CsCl/KCl flux. This is the first example of the single-crystal growth of a BiS 2 -based superconductor. The obtained single crystals had a plate-like shape with a size of 1-2 mm and a well-developed ab-plane. The crystal structure of the grown crystals was determined by single-crystal X-ray diffraction analysis to be the tetragonal space group P4/nmm (#129) with a = 3.996(3) Å and c = 13.464(6) Å. The chemical formula of the grown crystals was approximately Nd 0.98±0.06 O 0.7±0.

F-substituted ROBiS 2 (R = La, Ce, Nd) superconducting single crystals with different F concentration were grown successfully using CsCl/KCl flux. All the obtained single crystals had a plate-like shape with a well-developed ab-plane of 1-2 mm in size. The flux components of Cs, K, and Cl were not detected in the obtained single crystals by electron probe microanalysis. The grown single crystals of F-substituted LaOBiS 2 and CeOBiS 2 showed superconducting at about 3 K while the T c of the F-substituted NdOBiS 2 exhibited approximately 5 K. The superconducting anisotropy of the single crystals of F-substituted LaOBiS 2 and NdOBiS 2 was estimated to be 30-45 according to the effective mass model whereas those values were 13-21 for the F-substituted CeOBiS 2 single crystals. The F-substituted CeOBiS 2 single crystals exhibited magnetic order at about 7 K that apparently coexisted with superconductivity below around 3 K.