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.
Abstract Die koordinationsgetriebene Selbstorganisation ist eine der leistungsfähigsten Strategien zum Aufbau nanometergroßer diskreter (supra‐)molekularer Aggregate. Hier berichten wir über die Verwendung von zwei konstitutionsisomeren Bis(pyridin)‐Liganden auf der Basis von BINOL zu diesem Zweck. Je nach Substitutionsmuster des BINOL‐Gerüsts bilden sich bei der Koordination an Pd II ‐Ionen enantiomerenreine, endo ‐ oder exo ‐funktionalisierte sechs‐ oder zwölfkernige metallosupramolekulare Polyeder mit einem chiralen Gerüst. Die Aggregate wurden mittels NMR, MS, DLS, TEM und EELS sowie ECD charakterisiert. Die außergewöhnlich hohen molaren Circulardichroismen der Komplexe konnten durch den Vergleich experimenteller ECD‐Daten mit simulierten Daten (vereinfachte Tamm‐Dancoff‐Näherung zur zeitabhängigen DFT) nachvollzogen werden. Hervorzuheben ist ferner, dass die Selbstorganisationsprozesse vollständig selektiv im Sinne einer “narzisstischen” Selbsterkennung ablaufen, obwohl die Liganden ein hohes Maß an Rotationsfreiheit um die zentrale Aryl‐Aryl‐Bindung aufweisen.
Abstract A new bis(salicylimine) ligand based on the Tröger's base scaffold was synthesized in racemic and enantiomerically pure form. Upon coordination to zinc(II) ions this ligand undergoes highly diastereoselective self‐assembly into neutral dinuclear double‐stranded helicates as proven by XRD analysis and via comparison of experimental ECD spectra with those simulated with quantum‐chemical methods. When the racemic ligand was used, self‐assembly occurs under narcissistic self‐sorting resulting in the formation of a racemic pair of helicates as revealed by NMR spectroscopy and XRD analysis.
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.
Abstract The exceptional thermal stability of diarylethene closed isomers enabled many applications but also prevented utilization in photochromic systems that require rapid thermal reversibility. Herein, we report the diaryltriazolium ( DAT + ) photoswitch undergoing thermal cycloreversion within a few milliseconds and absorption of the closed form in the near‐infrared region above 900 nm. Click chemistry followed by alkylation offers modular and fast access to the electron‐deficient DAT + scaffold. In addition to excellent fatigue resistance, the introduced charge increases water solubility, rendering this photoswitch an ideal candidate for exploring biological applications.
Abstract We present (3+2)‐ and (4+2)‐cycloadditions of donor–acceptor (D–A) cyclopropanes and cyclobutanes with N‐sulfinylamines and a sulfur diimide, along with a one‐pot, two‐step strategy for the formal insertion of HNSO 2 into D–A cyclopropanes. These are rare examples of cycloadditions with D–A cyclopropanes and cyclobutanes whereby the 2π component consists of two different heteroatoms, thus leading to five‐ and six‐membered rings containing adjacent heteroatoms.
The so-called D4 model is presented for the accurate computation of London dispersion interactions in density functional theory approximations (DFT-D4) and generally for atomistic modeling methods. In this successor to the DFT-D3 model, the atomic coordination-dependent dipole polarizabilities are scaled based on atomic partial charges which can be taken from various sources. For this purpose, a new charge-dependent parameter-economic scaling function is designed. Classical charges are obtained from an atomic electronegativity equilibration procedure for which efficient analytical derivatives with respect to nuclear positions are developed. A numerical Casimir-Polder integration of the atom-in-molecule dynamic polarizabilities then yields charge- and geometry-dependent dipole-dipole dispersion coefficients. Similar to the D3 model, the dynamic polarizabilities are precomputed by time-dependent DFT and all elements up to radon (Z = 86) are covered. The two-body dispersion energy expression has the usual sum-over-atom-pairs form and includes dipole-dipole as well as dipole-quadrupole interactions. For a benchmark set of 1225 molecular dipole-dipole dispersion coefficients, the D4 model achieves an unprecedented accuracy with a mean relative deviation of 3.8% compared to 4.7% for D3. In addition to the two-body part, three-body effects are described by an Axilrod-Teller-Muto term. A common many-body dispersion expansion was extensively tested, and an energy correction based on D4 polarizabilities is found to be advantageous for larger systems. Becke-Johnson-type damping parameters for DFT-D4 are determined for more than 60 common density functionals. For various standard energy benchmark sets, DFT-D4 slightly but consistently outperforms DFT-D3. Especially for metal containing systems, the introduced charge dependence of the dispersion coefficients improves thermochemical properties. We suggest (DFT-)D4 as a physically improved and more sophisticated dispersion model in place of DFT-D3 for DFT calculations as well as other low-cost approaches like semi-empirical models.
