[18]Annulene

The geometry of [18]annulene has been fully optimized within the D_6h point group (la) utilizing ab initio MO theory at the STO-3G level to give carbon-carbon bond lengths of 1.391 and 1.400 Å. This structure is found to be 35.7 kcal/mol less stable than a D_3h structure (1b) with alternating bond lengths of 1.330 and 1.479 Å. The ionization potentials are calculated to be in the ranges. 6.2–7.1 (1a) and 7.4–8.1 eV (1b)     

Tetrakisdehydro[16]annuleno[18]annulene

Tetrakisdehydro[16]annuleno consisting of trisdehydro[16]annulene and bisdehydro[18] annulene has been synthesized. Induction of para- and diamagnetic ring currents in 16- and 18-membered rings, respectively, was clearly recognized by the ¹H NMR spectroscopy. A marked suppresion of the diatropicity in the 18π moiety was observed in the same trend as observed in tetrakisdehydro[14]annuleno[16]annulene.     

Tetrakisdehydro[18]annuleno[20]annulene

Tetrakisdehydro[18]annuleno[20]annulene has been synthesized. The ¹H NMR spectra clearly indicate the induction of dia- and paramagnetic ring currents in 18- and 20-rings, respectively. A marked suppression of the diatropicity in the 18π moiety was observed being in the same trend in other tetrakisdehydro[4n]annuleno[4n′+2]annulenes. The ¹H NMR spectroscopic behavior of the annulenoannulenes is consistent with theoretical conclusion.     

Subphthalocyanine-dehydro[18]annulenes

A subphthalocyanine trimer built around a dehydro[18]annulene core was prepared. The synthesis was achieved through direct homocoupling of an ortho-diethynyl-functionalized subphthalocyanine, obtained by palladium-catalyzed cross-coupling of the corresponding diiodo-subphthalocyanine with an ethynyl derivative. The lower analogue dehydro[12]annulene did not form in these homocoupling conditions. The trimers were fully characterized and their electrochemical properties investigated.     

[18F]CuCF3: A [18F]Trifluoromethylating Agent for Arylboronic Acids and Aryl Iodides

Positron emission tomography has emerged as the leading method for medical imaging with fluorine‐18 as the most widely used radioactive isotope. Here we report a semi‐automated method for the preparation of valuable [¹⁸F]trifluoromethylcopper, as well as its use for the radiosynthesis of [¹⁸F]trifluoromethylarenes and heteroarenes. Mild conditions of [¹⁸F]trifluoromethylation make this method particularly useful for the radiosynthesis of pharmacologically relevant [¹⁸F]trifluoromethylarenes and heteroarenes.     

Phosphatetrasilatricyclo[2.1.0.02,5]pentane

The phosphatetrasilatricyclo[2.1.0.0^2,5]pentane cage compound was synthesized by the reaction of the tetrasilacyclobutadiene dianion dipotassium salt precursor with PCl₃. The structure, bonding nature, and mechanism of formation of the title compound were studied both experimentally (NMR, X-ray) and computationally (DFT).     

Zur Oxydation intermetallischer Phasen: Die Oxoplumbate(II) K6[Pb2O5] [1] und K4[PbO3] [2]

On the Oxidation of Intermetallic Phases: The Oxoplumbates(II) K₆[Pb₂O₅] [1] and K₄[PbO₃] [2] Very pale yellow crystals of K₆[Pb₂O₅] were obtained by heating a wellground mixture of LiPb und K₂O₂ (K₂O₂: LiPb = 2.5:1) in Ag-tubes (550°C; 40 d). The crystal structure, triclinic, space group P1 , a = 1 326.7(6); b = 758.8(4); c = 637.0(3) pm; α = 92.17(3)°; β = 94.41(3)°; γ = 112.85(4)°; Z = 2 was determined (four-circle diffractometer data, Mo? K, 3 270 I_o(hkl), R = 8.0%, R_w = 3.5%, parameters see text). The pale yellow crystals of K₄[PbO3] were received by heating KPb and K₂O₂ (K₂O₂: KPb = 3.3:2) in Ni-tubes (450°C; 17 d). The crystal structure (orthorhombic, space group Pbca with a = 658.2(1); b = 1 131.8(4); c = 1 872.2(6) pm; Z = 8) was refined (four-circle diffractometer data, Mo? K, 2 003 I_o(hkl), R = 4.9%, R_w = 2.8%). The Madelung Part of Lattice Energy (MAPLE), Effective Coordination Numbers (ECoN), the Mean Fictive Ionic Radii (MEFIR) and the Charge Distribution (CHARDI) are being calculated for both oxides.     

Electrochemical transfer of [18F]fluoride from [18O]water into organic solvents ready for labeling reactions

For labeling reactions [¹⁸F]fluoride has to be separated from [¹⁸O]water and transferred into an organic solvent suitable for nucleophilic substitutions. An electrolytical method is described for depositing [¹⁸F]fluoride on a vitreous carbon electrode and releasing it directly into CH₃CN or DMSO. In the presence of Et₃N×3HF, [¹⁸F]fluoride is almost quantitatively released into acetonitrile. When using n.c.a conditions, i.e., Et₃N^.HCl, desorption of the ¹⁸F activity is almost 70% and 60% in acetonitrile and DMSO, respectively, already within 5 minutes.