Holger Ott

Periphery‐Substituted [4+6] Salicylbisimine Cage Compounds with Exceptionally High Surface Areas: Influence of the Molecular Structure on Nitrogen Sorption Properties

The synthesis of various periphery-substituted shape-persistent cage compounds by twelve-fold condensation reactions of four triptycene triamines and six salicyldialdehydes is described, where the substituents systematically vary in bulkiness. The resulting cage compounds were studied as permanent porous material by nitrogen sorption measurements. When the material is amorphous, the steric demand of the cages exterior does not strongly influence the gas uptake, resulting in BET surface areas of approximately 700u2005m(2) u2009g(-1) for all cage compounds 3u2009c-e, independently of the substituents bulkiness. In the crystalline state, materials of the same compounds show a strong interconnection between steric demand of the peripheral substituent and the resulting BET surface area. With increasing bulkiness, the overall BET surface area decreases, for example 1291u2005m(2) u2009g(-1) (for cage compoundu20053u2009c with methyl substituents), 309u2005m(2) u2009g(-1) (for cage compound 3u2009d with 2-(2-ethyl-pentyl) substituents) and 22u2005m(2) u2009g(-1) (for cage compound 3u2009e with trityl substituents). Furthermore, we found that two different crystalline polymorphs of the cage compoundu20053u2009a (with tert-butyl substituents) differ also in nitrogen sorption, resulting in a BET surface area of 1377u2005m(2) g(-1), when synthesized from THF and 2071u2005m(2) g(-1), when recrystallized from DMSO.

Lanthanide-polyphosphonate coordination polymers combining catalytic and photoluminescence properties.

A rapid, mild and high-yield microwave synthesis of 1D isotypical [Ln(H4bmt)(H5bmt)(H2O)2]·3H2O coordination polymers is presented. The La(3+)-based material is highly active as a heterogeneous catalyst in the methanolysis of styrene oxide at nearly room temperature. Eu(3+)- and Tb(3+)-doped materials are very effective UV-to-visible light converters.

A rare alb-4,8-Cmce metal–coordination network based on tetrazolate and phosphonate functionalized 1,3,5,7-tetraphenyladamantane

Symmetric tetrahedral ligands are prominent, but somewhat under-investigated building blocks for the generation of coordination polymeric networks. Coordination networks [Mn5Cl2(L1)2(H2O)4(DMF)4]·3H2O·7DMF, 1 and the [La2(H5L2)2(H2O)6], 2 are synthesized under mild solvothermal methods in DMF from the adamantane-based tetrahedral ligands, 1,3,5,7-tetrakis(4-phenyltetrazol-5-yl)adamantane (H4L1), reported for the first time, and 1,3,5,7-tetrakis(4-phenylphosphonic acid)adamantane (H8L2), respectively. Compounds 1 and 2 are based on completely different pentanuclear and binuclear secondary metal building units, respectively, and have different symmetries, but demonstrate an interesting coincidence of underlying topologies, which could be interpreted as a directing or ‘imprinting’ effect of the symmetry of the rigid tetrahedral ligands. Both structures represent examples of a rarely observed (4,8)-coordinated net. The χMT product for 1 at room temperature is slightly lower than the expected for five Mn(II) ions with S = 5/2 and g ≈ 1.98 and on lowering the temperature χMT approaches the expected value for a single Mn(II) as a result of the antiferromagnetic coupling through the tetrazolate bridges.

Precrystalline Aggregates Enable Control over Organic Crystallization in Solution

Understanding and controlling organic crystallization in solution is a long-standing challenge. Herein, we show that crystallization of an aromatic amphiphile based on perylene diimide in aqueous media involves initially formed amorphous spherical aggregates that evolve into the crystalline phase. The initial appearance of the crystalline order is always confined to the spherical aggregates that are precursors for crystalline evolution. The change in the solvation of the prenucleation phase drives the crystallization process towards crystals that exhibit very different structure and photofunction. The initial molecular structure and subsequent crystal evolution can be regulated by tuning the hydrophobicity at various stages of crystallization, affording dissimilar crystalline products or hindering crystallization. Thus, the key role of the precrystalline states in organic crystal evolution enables a new strategy to control crystallization by precrystalline state manipulation.

Preparation and characterization of trimethylsilyl-substituted benzimidazole metal complexes and structural characterization of dichlorobis[1-(trimethylsilyl)methyl-1H-benzimidazole-κ N 3]cobalt(II)

The ligands 1-trimethylsilylmethylbenzimidazole, 5-methyl-1-trimethylsilylmethylbenzimidazole, and 5-nitro-1-trimethylsilylmethylbenzimidazole and their Co(II) and Zn(II) complexes were synthesized and characterized by 1H-NMR, 13C-NMR, and elemental analyses. The crystal structure of dichlorobis[1-(trimethylsilyl)methyl-1H-benzimidazole-κN 3]cobalt(II) has been determined by single crystal X-ray diffraction.

Quantum Crystallography: Current Developments and Future Perspectives

Crystallography and quantum mechanics have always been tightly connected because reliable quantum mechanical models are needed to determine crystal structures. Due to this natural synergy, nowadays accurate distributions of electrons in space can be obtained from diffraction and scattering experiments. In the original definition of quantum crystallography (QCr) given by Massa, Karle and Huang, direct extraction of wavefunctions or density matrices from measured intensities of reflections or, conversely, ad hoc quantum mechanical calculations to enhance the accuracy of the crystallographic refinement are implicated. Nevertheless, many other active and emerging research areas involving quantum mechanics and scattering experiments are not covered by the original definition although they enable to observe and explain quantum phenomena as accurately and successfully as the original strategies. Therefore, we give an overview over current research that is related to a broader notion of QCr, and discuss options how QCr can evolve to become a complete and independent domain of natural sciences. The goal of this paper is to initiate discussions around QCr, but not to find a final definition of the field.

CAPOW: a standalone program for the calculation of optimal weighting parameters for least-squares crystallographic refinements

A new standalone program to calculate optimized values for weighting parameters, CAPOW, is presented along with enhanced visualization tools for analysing statistical distributions of data.