Next Generation Copper Mediators for the Efficient Production of 18 F-Labeled Aromatics.

Cu-mediated radiofluorination is a versatile tool for the preparation of 18 F-labeled (hetero)aromatics. In this work, we systematically evaluated a series of complexes and identified several generally applicable mediators for highly efficient radiofluorination of aryl boronic and stannyl substrates. Utilization of these mediators in nBuOH/DMI or DMI significantly improved 18 F-labeling yields despite use of lower precursor amounts. Impressively, application of 2.5 µmol aryl boronic acids was sufficient to achieve 18 F-labeling yields of up to 75 %. The practicality of the novel mediators was demonstrated by efficient production of five PET-tracers and transfer of the method to an automated radiosynthesis module. In addition, (S)-3-[18 F]FPhe and 6-[18 F]FDOPA were prepared in activity yields of 23±1 % and 30±3 % using only 2.5 µmol of the corresponding boronic acid or trimethylstannyl precursor.

Eu(O2 C-C≡C-CO2 ): An EuII Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion.

Anhydrous EuII -acetylenedicarboxylate (EuADC; ADC2- = - O2 C-C≡C-CO2 - ) was synthesized by reaction of EuBr2 with K2 ADC or H2 ADC in degassed water under oxygen-free conditions. EuADC crystallizes in the SrADC type structure (I41 /amd, Z=4) forming a 3D coordination polymer with a diamond-like arrangement of Eu2+ nodes (msw topology including the connecting ADC2- linkers). Deep orange coloured EuADC is stable in air and starts decomposing upon heating in an argon atmosphere only at 440 °C. Measurements of the magnetic susceptibilities (µeff =7.76 µB ) and 151 Eu Mössbauer spectra (δ=-13.25 mm s-1 at 78 K) confirm the existence of Eu2+ cations. Diffuse reflectance spectra indicate a direct optical band gap of Eg =2.64 eV (470 nm), which is in accordance with the orange colour of the material. Surprisingly, EuADC does not show any photoluminescence under irradiation with UV light of different wavelengths. Similar to SrADC, EuADC exhibits a negative thermal volume expansion below room temperature with a volume expansion coefficient αV =-9.4(12)×10-6  K-1 .

How Does the Fluorination of the Linker Affect the Stability of Trimesate-Based Coordination Polymers and Metal-Organic Frameworks?

The syntheses and crystal structures of the monopotassium salts of difluorinated and tri/perfluorinated trimesic acid (1,3,5-benzenetricarboxylic acid ≡ H3BTC) are presented, namely, K(H2 dF-BTC) ( Fdd2, Z = 16) and K(H2 pF-BTC) ( Cc, Z = 4). For the first time, together with already known K(H2 mF-BTC), all fluorination degrees of trimesic acid are accessible and can be used for a systematic study of the influence of fluorination on the stability of the resulting coordination polymers and metal-organic frameworks (MOFs). The monopotassium salts show a decreasing (chemical) stability in water upon heating, as well as a decreasing thermal stability, as evidenced by differential scanning calorimetry/thermogravimetric analysis (DSC/TGA). A similar decreasing thermal stability is found for two series of isostructural coordination polymers (UHM-33 topology: ∞2[Cu2(L)2(DMA)2]·2DMA with L2- = H mF-BTC2- and H dF-BTC2-) and MOFs (∞3[Ba(L)(H2O)2]·1/2H2O with L2- = HBTC2-, H mF-BTC2- and H dF-BTC2-). Remarkably, while the decomposition temperatures decrease with increasing fluorination of the linker, the releasing temperatures for embedded solvent molecules (DMA and H2O, respectively) increase. To identify possible candidates for the synthesis of isostructural coordination polymers and MOFs with BTC3- ligands with different degrees of fluorination, a database-adapted approach was developed, which utilizes the increased torsion angle between the carboxylate groups and the phenyl rings in these materials as a structure-determining parameter.