The least-coordinating anion [(RFO)3Al–F–Al(ORF)3]– and its more Lewis-basic brother [F–Al(ORF)3]– (RF = C(CF3)3).

Perovskite‐related 2D‐compounds of the series 5‐AVA2MAn–1PbnBr3n–1 were synthesised and characterised for the representatives with n = 1, 2, and 3 [5‐AVA = 5‐amino valerian acid cation, HOOC(CH2)4NH3+]. In addition, we have investigated the chloride compound 5‐AVA2PbCl4 and the binary compounds 5‐AVAX (X = Cl, Br). The crystal structures of the 2D compounds represent well‐known cut‐outs of the cubic 3D perovskites with layers of corner‐sharing PbBr6 octahedrons in (100) orientation. According to the value of n the layer thickness comprises one, two or three layers. Similar to most of the perovskite‐related representatives the PbBr6 octahedrons are rotated, but with slight differences. We have analysed the rotation pattern with respect to the different aspects of hydrogen bonding and orientation of the organic cations 5‐AVA+ and MA+. Measurements of the optical properties reveal a decrease of the band gap from 3.02 eV (n = 1) over 2.80 eV (n = 2) to 2.70 eV (n = 3). For 5‐AVA2PbBr4 we observed strong blue fluorescence (413 nm) with a remarkably small Strokes shift (47 nm). All investigations were influenced by the reduced stability of the representatives with n = 2 and n = 3 with respect to the degradation into the simpler compounds 5‐AVA2PbBr4 and MAPbBr3. This is in contrast to similar 2D‐iodides, where many representatives are known and n can reach values up to 6 and 7. Our series with n = 1, 2, and 3 represent the third example for a series of compounds with n = 1–3.

Pale-yellow single crystals of the new borate tellurate(VI) Bi TeBO were obtained by reaction of stoichiometric amounts of Bi O , B O , and Te(OH) at 780 °C. The non-centrosymmetric crystal structure (P6 , Z=2, a=8.7454(16), c=5.8911(11) Å, 738 refl., 43 param, R1=0.037, wR2=0.093) contains isolated trigonal-planar BO units and nearly undistorted TeO octahedra. The Bi cations are located in between in octahedral voids. The BiO octahedra are significantly distorted to a [3+3] pattern (2.25/2.50 Å) due to the ns configuration. According to the structural features, the formula can be written as Bi (TeO )(BO ). Alternatively, the structure can also be described as hcp of oxygen with Te and Bi in octahedral voids and B in trigonal- planar voids. The vibrational spectra show the typical features of BO and TeO units with a significant B/ B isotopic splitting of the IR-active B-O valence mode (1248 and 1282 cm ). The UV/Vis spectrum shows an optical band edge with an onset around 480 nm (2.6 eV). MAS-NMR spectra of B show an anisotropic signal with a quadrupole coupling constant of C =2.55 MHz. and a very small deviation from rotational symmetry (η=0.2). The isotropic chemical shift is 20.1 ppm. The second harmonic generation (SHG) test was positive with an activity comparable to potassium dihydrogen phosphate (KDP). Bi TeBO decomposes in air at 825 °C to Bi TeO .