Successive photoswitching and derivatization effects in photochromic dithienylethene-based coordination cages

A new series of [Pd2(L)4] cages based on photochromic dithienylethene (DTE) ligands allowed us to gain insight into the successive photoswitching of multiple DTE moieties in a confined metallo‐supramolecular assembly. Three new X‐ray structures of [Pd2(o‐L4)4], [Pd2(o‐L1)2(c‐L1)2] and [Pd2(c‐L1)4] (o‐L and c‐L = open and closed forms of DTE ligands, respectively) were obtained. The structures deliver snapshots of three different combinations of DTE photoisomeric states within the cage, facilitating a comparison of the all‐open with the all‐closed, and most notably, an intermediate form where open and closed switches co‐exist in the same cage. Moreover, a series of spherical anionic borate clusters was introduced in order to study their roles in the light‐controllable host–guest chemistry. The binding guests show higher affinities with the flexible open cage [Pd2(o‐L1)4] than with the rigid closed cage [Pd2(c‐L1)4]. For the [B12F12]2− guest, thermodynamic data obtained from NMR experiments was compared to results from isothermal titration calorimetry (ITC)

On the temperature dependence of H-U iso in the riding hydrogen model

The temperature dependence of H-Uiso in N-acetyl-L-4-hydroxyproline monohydrate is investigated. Imposing a constant temperature-independent multiplier of 1.2 or 1.5 for the riding hydrogen model is found to be inaccurate, and severely underestimates H-Uiso below 100 K. Neutron diffraction data at temperatures of 9, 150, 200 and 250 K provide benchmark results for this study. X-ray diffraction data to high resolution, collected at temperatures of 9, 30, 50, 75, 100, 150, 200 and 250 K (synchrotron and home source), reproduce neutron results only when evaluated by aspherical-atom refinement models, since these take into account bonding and lone-pair electron density; both invariom and Hirshfeld-atom refinement models enable a more precise determination of the magnitude of H-atom displacements than independent-atom model refinements. Experimental efforts are complemented by computing displacement parameters following the TLS+ONIOM approach. A satisfactory agreement between all approaches is found

One-Electron-Mediated Rearrangements of 2,3-Disiladicarbene

A disiladicarbene, (Cy-cAAC)2Si2 (2), was synthesized by reduction of Cy-cAAC:SiCl4 adduct with KC8. The dark-colored compound 2 is stable at room temperature for a year under an inert atmosphere. Moreover, it is stable up to 190 °C and also can be characterized by electron ionization mass spectrometry. Theoretical and Raman studies reveal the existence of a Si═Si double bond with a partial double bond between each carbene carbon atom and silicon atom. Cyclic voltammetry suggests that 2 can quasi-reversibly accept an electron to produce a very reactive radical anion, 2•–, as an intermediate species. Thus, reduction of 2 with potassium metal at room temperature led to the isolation of an isomeric neutral rearranged product and an anionic dimer of a potassium salt via the formation of 2•–

CCDC 1825759: Experimental Crystal Structure Determination

Related Article: Changsheng Wu, Helga U. van der Heul, Alexey V. Melnik, Jens Lübben, Pieter C. Dorrestein, Adriaan J. Minnaard, Young Hae Choi, Gilles P. van Wezel|2019|Angew.Chem.,Int.Ed.|58|2809|doi:10.1002/anie.201814581,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.