Structure Determination of Biogenic Crystals Directly from 3D Electron Diffraction Data.

Highly reflective assemblies of purine, pteridine, and flavin crystals are used in the coloration and visual systems of many different animals. However, structure determination of biogenic crystals by single-crystal XRD is challenging due to the submicrometer size and beam sensitivity of the crystals, and powder XRD is inhibited due to the small volumes of powders, crystalline impurity phases, and significant preferred orientation. Consequently, the crystal structures of many biogenic materials remain unknown.

Electron crystallography and dedicated electron-diffraction instrumentation.

Electron diffraction (known also as ED, 3D ED or microED) is gaining momentum in science and industry. The application of electron diffraction in performing nano-crystallography on crystals smaller than 1 µm is a disruptive technology that is opening up fascinating new perspectives for a wide variety of compounds required in the fields of chemical, pharmaceutical and advanced materials research. Electron diffraction enables the characterization of solid compounds complementary to neutron, powder X-ray and single-crystal X-ray diffraction, as it has the unique capability to measure nanometre-sized crystals.

Synthesis, detailed geometric analysis and bond-valence method evaluation of the strength of π-arene bonding of two isotypic cationic prehnitene tin(II) complexes: [{1,2,3,4-(CH)CH}SnCl][Cl] ( = Al and Ga).

From solutions of prehnitene and the ternary halides (SnCl)[Cl] ( = Al, Ga) in chloro-benzene, the new cationic Sn-π-arene complexes -poly[[chlorido-aluminate(III)]-tri-μ-chlorido-4':1κ ,1:2κ -[(η-1,2,3,4-tetra-meth-yl-benzene)-tin(II)]-di-μ-chlorido-2:3κ -[(η-1,2,3,4-tetra-methyl-benzene)-tin(II)]-di-μ-chlorido-3:4κ -[chlorido-aluminate(III)]-μ-chlorido-4:1'κ ], [AlSnCl(CH)] , () and -poly[[chlorido-gallate(III)]-tri-μ-chlor-ido-4':1κ ,1:2κ -[(η-1,2,3,4-tetra-methyl-benzene)-tin(II)]-di-μ-chlorido-2:3κ -[(η-1,2,3,4-tetra-methyl-benzene)-tin(II)]-di-μ-chlorido-3:4κ -[chlor-ido-gallate(III)]-μ-chlorido-4:1'κ ], [GaSnCl(CH)] , (), were isolated. In these first main-group metal-prehnitene complexes, the distorted η arene π-bonding to the tin atoms of the SnCl moieties in the centre of [{1,2,3,4-(CH)CH}SnCl][Cl] repeating units (site symmetry ) is characterized by: (i) a significant ring slippage of 0.4 Å indicated by the dispersion of Sn-C distances [: 2.