A hypothesis of limiting fragmentation of the target and of the projectile in a high-energy lepton-hadron or hadron-hadron collision is defined. Arguments are given for the hypothesis. Comparisons with various models and concepts are made. Further speculations are made, including the absence of pionization processes in high-energy collisions and the dependence of multiplicity on the momentum transfer. Experiments are suggested.

The metallocene-based linker molecule 1,1′-ferrocenedicarboxylic acid (H2FcDC) was used to synthesize four different polymorphs of composition [In­(OH)­(FeC12H8O4)]. Using conventional solvent-based synthesis methods and varying the synthetic parameters such as metal source, reaction temperature, and solvent, two different MOFs and one 1D-coordination polymer denoted as CAU-43 (1), In-MIL-53-FcDC_a (2), and In-FcDC (3) were obtained. Furthermore, thermal treatment of CAU-43 (1) at 190 °C under vacuum yielded a new polymorph of 2, In-MIL-53-FcDC_b (4). Both MOFs 2 and 4 crystallize in a MIL-53 type structure, but in different space groups C2/m for 2 and P1̅ for 4. The structures of the four title compounds were determined by single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), or a combination of three-dimensional electron diffraction measurements (3D ED) and PXRD. N2 sorption experiments of 1, 2, and 4 showed specific surface areas of 355 m2 g–1, 110 m2 g–1, and 140 m2 g–1, respectively. Furthermore, the electronic properties of the title compounds were characterized via Mössbauer and EPR spectroscopy. All Mössbauer spectra showed the characteristic doublet, proving the persistence of the ferrocene moiety. In the cases of 1, 3, and 4, appreciable impurities of ferrocenium ions could be detected by electron paramagnetic resonance spectroscopy. Cyclovoltammetric experiments were performed to demonstrate the accessible redox activity of the linker molecule of the title compounds. A redox process of FcDC2– with oxidation (between 0.86 and 0.97 V) and reduction wave (between 0.69 and 0.80 V) was observed.

The intercalation of different pyrazines (pyrazine, methylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine) into the trans-1,4-cyclohexanedicarboxylate (CDC 2-) based Al-MOF [Al(OH)(CDC)], denoted as CAU-13, was investigated. The adsorption of the guest molecules into the flexible MOF was carried out from aqueous solution or via vapour phase adsorption, starting with the hydrated narrow-pore form of the framework [Al(OH)(O2C-C6H10-CO2)]·H2O (CAU-13-np). The obtained host-guest systems were characterised by thermogravimetry and vibrational spectroscopy and their crystal structures were elucidated using powder X-ray diffraction (PXRD) data. The crystal structures indicate that guest molecules forming hydrogen-bonds with the host framework (pyrazine, methylpyrazine and 2,5-dimethylpyrazine) induce a slight opening of the channels, resulting in a semi-open framework conformation (CAU-13-so). For the bulkier guests 2,3-dimethylpyrazine, trimethylpyrazine and tetramethylpyrazine, only Van der Waals contacts can be observed between the host and the guest molecules and the large pore conformation is observed (CAU-13-lp). We carried out in-situ PXRD studies using synchrotron radiation during the adsorption of the respective guest molecules from aqueous solutions with various concentrations and at different temperatures. In general, stronger host-guest interactions required milder adsorption conditions while harsher conditions nevertheless accelerated the conversion. The kinetic parameters for the intercalation of pyrazine indicate that the rate limiting step differs, depending on the intercalation temperature.