RESUMEN
Two-dimensional (2D) halide perovskites exhibit unique structural and optical properties because large organic molecular cations distort the perovskite structure and the excitons confined in the 2D layers are stable. Here, we report the temperature dependences of the absorption spectra, second harmonic generation (SHG) intensity, and lattice constants of 2D perovskite (BA)2(EA)2Pb3I10 single crystals, where BA is n-butylammonium and EA is ethylammonium. We found that the Urbach tail of the absorption spectrum significantly changes at around 200 K and that the change is correlated with the SHG intensity and the in-plane lattice distortion. We concluded that a random distribution of spontaneous polarizations in the ferroelectric phase modifies the linewidth of the band-edge exciton transition and is the cause of the anomalous temperature dependence of the steepness parameter of the Urbach tail.
RESUMEN
Development of silylating reagents that can transfer a wide range of silyl groups has been a long-standing challenge. Herein we report sodium diphenylsilylsilanolates as new stable and handy silylating reagents that could be synthesized from chlorosilanes. The new reagents retain the ability of dimethylsilylsilanolates for the delivery of a variety of silyl groups in palladium-catalyzed silylation of aryl bromides irrespective of the steric and electronic properties of silyl groups to be transferred.
