Trapping x‐ray radiation damage from homolytic Se–C bond cleavage in BnSeSeBn crystals (Bn=benzyl, CH2C6H5)

Irradiation of dibenzyl diselenide BnSeSeBn with X-ray or UV-light cleaves the Se-C and the Se-Se bonds, inducing stable and metastable radical states. They are inevitably important to all natural and life sciences. Structural changes due to X-ray-induced Se-C bond-cleavage could be pin-pointed in various high-resolution X-ray diffraction experiments for the first time. Extended DFT methods were applied to characterize the solid-state structure and support the refinement of the observed residuals as contributions from the BnSeSe • radical species. The X-ray or UV-irradiated crystalline samples of BnSeSeBn were characterized by solid-state EPR. This paper provides insight that in the course of X-ray structure analysis of selenium compounds not only organo-selenide radicals like RSe • may occur, but also organo diselenide BnSeSe • radicals and organic radicals R • are generated, particularly important to know in structural biology

Kristallographische Datenbanken Systematische Ueberpruefung von Strukturen auf hoehere Symmetrie und Untersuchungen zur Konformation von 1,3-Oxazolidinen und Phenylsulfonamiden

SIGLEAvailable from TIB Hannover: DW 1519 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Non-merohedral twinning: From minerals to proteins

In contrast to twinning by merohedry, the reciprocal lattices of the different domains of non-merohedral twins do not overlap exactly. This leads to three kinds of reflections: reflections with no overlap, reflections with an exact overlap and reflections with a partial overlap of a reflection from a second domain. This complicates the unit-cell determination, indexing, data integration and scaling of X-ray diffraction data. However, with hindsight it is possible to detwin the data because there are reflections that are not affected by the twinning. In this article, the successful solution and refinement of one mineral, one organometallic and two protein non-merohedral twins using a common strategy are described. The unit-cell constants and the orientation matrices were determined by the program CELL_NOW. The data were then integrated with SAINT. TWINABS was used for scaling, empirical absorption corrections and the generation of two different data files, one with detwinned data for structure solution and refinement and a second one for (usually more accurate) structure refinement against total integrated intensities. The structures were solved by experimental phasing using SHELXT for the first two structures and SHELXC/D/E for the two protein structures; all models were refined with SHELXL.IU acknowledges grants BIO2015-64216-P and MDM2014-0435 from the Spanish Ministry of Science and Innovation and EU FEDER

Bi- and tricyclic penta- and hexacoordinated phosphoranes with varying ring sizes: synthesis, structures, and reactivity

New tricyclic hexacoordinated phosphoranes 1-6 with internal N→P coordination containing ring sizes varying from five to eight membered have been synthesized by oxidative addition of a quinone or a diol to a cyclic phosphite. The bicyclic phosphorane (NC9H6O)P(O2(3,5-t-Bu)2C6H2)((O-2,4-(t-Bu)2C6H2)2CH2).½H2O (7.½H2O) has been synthesized by adding the 3,5-di-tert-butyl-o-benzoquinone to the cyclic phosphite. The compound (NC9H6O)P(2,2'-OC6H4C6H4O)2 (6) results from a novel ring exchange reaction of a phosphorinane by a phosphepin in two ways: (a) by treating (OCH2CMe2CH2O)P((OC9H6N) with 2,2'-biphenol/N-chlorodiisopropylamine and (b) by treating (Et2N)P(OCH2CMe2CH2O)(2,2'-OC6H4C6H4O) with 8-hydroxyquinoline. Treatment of the aminophosphorane (Et2N)P(OCH2CMe2CH2O)(O2C14H8) with 2,4,6-trimethylbenzoic acid led to the unique ester (OCH2CMe2CH2O)P(O){OC14H8O(C(O)-2,4,6-Me3C6H2)} (10). 31P NMR data for the new compounds are discussed with respect to the differing ring sizes and coordination number on phosphorus. X-ray analysis shows hexacoordination in 2, 4, and 6 with an N→P bond and pentacoordination in 7 without an N→P bond. The coordinating nitrogen is trans to an oxygen of the six-membered ring in 2 and of the seven-membered ring in 4. The eight-membered ring in 7 spans a diequatorial position in a trigonal bipyramidal arrangement

Cyclic aminophosphites and -phosphoranes possessing six- and higher-membered rings: a comparative study of structure and reactivity

Aminophosphoranes 2 and 4-9 with a cyclohexylamino substituent and ring sizes varying from five to eight have been synthesized by oxidative addition reactions of cyclic aminophosphites with diols or 1,2-diketones. The reactivities of these phosphoranes are compared with those of the corresponding cyclic aminophosphites. The difference in hydrolytic pathways between amino- and analogous phenoxyphosphoranes is discussed. X-ray structures of two sets of compounds, (a) (C6H11NH)P(OCH2CMe2CH2O) (1) and (C6H11NH)P(OCH2CMe2CH2O)(1,2-O2C6Cl4) (2) and (b) (C6H11NH)P{O-(t-Bu)2C6H2)2CH2} (3) and (C6H11NH)P{(O-(t-Bu)2C6H2)2CH2}(1,2-O2C6H4)·½Et2O (4·½Et2O) have been determined and geometrical parameters compared between the P(III) and the corresponding P(V) compounds. In 1, the six-membered ring has a chair conformation with the amino group axial; in 2, the six-membered ring is located apical-equatorial in a trigonal bipyramidal geometry and has a boat conformation. The eight-membered ring has a boat-chair conformation in 3, whereas the same ring has a tub conformation in 4

Formation and structure of the oxygen-centered lead thiolate cluster Pb5O(SRF)(8)center dot 2C(7)H(8) [R-F=2,4,6-tris(trifluoromethyl)phenyl]

The unusual pentanuclear lead thiolate cluster PbsO(SRF)(8).C2H8 (3) (C7H8 = toluene) has been obtained by oxidation of Pb(SRF)(2) (2) with dry air and structurally characterized. The central oxygen atom is coordinated to three lead atoms in a trigonal planar fashion. The coordination sphere of the other two lead atoms is completed by coordination of toluene molecules