Syntheses and structures of three new lanthanide coordination compounds with dithiocarbamate ligands are reported. The complexes [Ln(Me(2)dtc)(3)(phen)] (Ln = Pr (1), Nd (2) and Gd (3), Me(2)dtc = N,N-dimethyldithiocarbamate and phen = 1,10-phenanthroline) were synthetized by a simple metathesis between lanthanide(III) nitrate and sodium dimethyldithiocarbamate followed by addition of 1,10-phenanthroline without the exclusion of moisture. Single crystal X-ray analysis showed that all three complexes are isostructural, crystallizing in the triclinic space group P (1) over bar. The Ln-S and Ln-N bond lengths decrease in agreement with the decrease in ionic radii across the lanthanide series. Similar structures with Et(2)dtc ligands show no significant effect on the changes of Ln-S bond lengths and also on the S-Ln-S bite angles. The crystal packing of described complexes is formed via pi-pi stacking interactions and C-H center dot center dot center dot S non-covalent contacts.
We summarize exploratory work on multigrain crystallography. The experimental arrangement comprises a monochromatic beam, a fully illuminated sample with up to several hundred grains in transmission geometry on a rotary table and a 2D detector. Novel algorithms are presented for indexing, integration and filtering with emphasis on handling the complications of spot overlap and the need for on-line analysis. The structure solution and refinement steps are performed by conventional single crystal programs. Simulations are used to verify the algorithms and to probe the overall limitations of the methodology in terms of number of grains, size of unit cell and direct space resolution. First experimental results in the fields of chemistry, structural biology and time-resolved studies in photochemistry are presented. As an outlook, the concept of Total Crystallography is introduced, defined as the simultaneous characterization of the 3D atomic, and 3D grain-scale structure of polycrystalline specimens with phases of unknown composition and structure.
Abstract Theory and principles of the three-dimensional pair distribution function analysis of disordered single crystals are introduced. The mathematical framework is presented and the appearance of pair distribution function patterns is discussed on the examples of some basic disorder models. It is further demonstrated how pair distribution function maps are affected by typical experimental problems. Approaches for a better understanding of such effects and strategies for a proper handing of artifacts in diffuse scattering experiments are proposed.
