Fraser White

A Permanent Mesoporous Organic Cage with an Exceptionally High Surface Area

Recently, porous organic cage crystals have become a real alternative to extended framework materials with high specific surface areas in the desolvated state. Although major progress in this area has been made, the resulting porous compounds are restricted to the microporous regime, owing to the relatively small molecular sizes of the cages, or the collapse of larger structures upon desolvation. Herein, we present the synthesis of a shape-persistent cage compound by the reversible formation of 24 boronic ester units of 12 triptycene tetraol molecules and 8 triboronic acid molecules. The cage compound bears a cavity of a minimum inner diameter of 2.6 nm and a maximum inner diameter of 3.1 nm, as determined by single-crystal X-ray analysis. The porous molecular crystals could be activated for gas sorption by removing enclathrated solvent molecules, resulting in a mesoporous material with a very high specific surface area of 3758 m(2)  g(-1) and a pore diameter of 2.3 nm, as measured by nitrogen gas sorption.

LaZn12.37 (1), a zinc-deficient variant of the NaZn13 structure type

The title compound (lanthanum dodecazinc), LaZn12.37 (1), is confirmed to be a nonstoichiometric (zinc-deficient) modification of the NaZn13 structure type, in which one Zn atom (Wyckoff site 8b, site symmetry m ) has a fractional site occupancy of 0.372 (11). The other Zn atom (96i, m) and the La atom (8a, 432) are fully occupied. The coordination polyhedra of the Zn atoms are distorted icosahedra, whereas the La atoms are surrounded by 24 Zn atoms, forming pseudo-Frank–Kasper polyhedra. Electronic structure calculations indicate that Zn—Zn bonding is much stronger than La—Zn bonding.

{4-Hy-droxy-N'-[(2E,3Z)-4-oxido-4-phenyl-but-3-en-2-yl-idene]benzo-hydrazidato}dimethyl-tin(IV).

The SnIV atom in the title compound, [Sn(CH3)2(C17H14N2O3)], is five-coordinated within a C2N2O donor set provided by the N,N,O-tridentate ligand and two methyl groups. The resultant coordination geometry is intermediate between trigonal-bipyramidal and square-pyramidal. In the crystal, supramolecular zigzag chains propagating along the c- axis direction are mediated by O—H⋯O hydrogen bonds, and weak C—H⋯π interactions consolidate the packing.

Use of silver radiation for crystallographic studies

Traditionally, the most widely used laboratory X-ray diffraction sources have used either molybdenum or copper targets to produce monochromatic beams. Whilst longer wavelength radiation such as copper Kα has benefits in the fields of protein crystallography and, absolute structure determination among others, this longer wavelength is unsuitable for certain types of studies such as obtaining high resolution charge density data, collecting data on highly absorbing samples, or achieving acceptable completeness in high pressure experiments through the limiting window of a diamond anvil cell. With the recent improvements to the high flux micro-focus source technology in Rigaku’s PhotonJet sources, short wavelength radiation silver Kα has become a more viable option to address some of these problems. Coupled with a hybrid photon counting detector using a cadmium telluride sensor which is designed specifically for maximum performance with the wavelength of a silver Kα PhotonJet, the XtaLAB Synergy-S is the perfect research instrument for uses in fields such as high pressure and charge density, or for highly absorbing samples.

Improving your single-crystal data collection

Performing data collections which are not only high quality but also efficient is a key requirement of diffractometer users around the world, either to enable high throughput, or simply maximise data quality in a given time. By using a rapid structural analysis before the start of your data collection, you can improve the overall strategy and data quality of your sample. Combining this new approach to data collection with the high speed of the latest instruments, e.g XtaLAB Synergy-S, gives crystallographers the tools to achieve the best possible structures for publication.

Handling difficult samples: data-processing improvements

A research project will often define at its inception a material or family of closely related materials for study. Sometimes obtaining crystal structure(s) is deemed to be highly useful and of high importance, yet unforeseen problems in obtaining high quality diffraction data can lead to difficulties in realising project goals. This may be for a number of reasons such as sample sensitivities, a propensity for twinning or simply weak diffraction.

A new interface to the Cambridge Structural Database (CSD) inCrysAlisPro

With some X-ray diffraction experiments taking many hours to complete, instrument time is a valuable commodity. The accidental recollection of known samples is an undesirable event and for this reason many crystallographers rely on databases of unit cells to identify matches and eliminate wasteful data collections. To facilitate this process a newly developed module within the data collection software package, CrysAlisPro, provides a simple user friendly interface allowing automatic unit cell checking against known cells found in the CSD. Developed in conjunction with the Cambridge Crystallographic Data Centre (CCDC), this module is freely available to all Agilent CrysAlisPro users.