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The title compound, C₈H₁₈NO₂⁺·Br⁻·C₈H₁₇NO₂, crystallizes as the bromide salt of a 50:50 mixture of (triethylazaniumyl)carboxylic acid and the zwitterionic (triethylazaniumyl)carboxylate. The two organic entities are linked by a half-occupied bridging carboxylic acid hydrogen atom that is hydrogen-bonded to the carboxylate group of the second molecule. The tetralkylammonium group adopts a nearly perfect tetrahedral shape around the nitrogen atom with bond lengths that agree with known values. The carboxylic acid/carboxylate group is orientedantito one of the ethyl groups on the ammonium group, and the carbonyl oxygen atom is engaged in intramolecular C—H...O hydrogen bonds. 

The molecular structure of the tripodal carbamoylmethylphosphine oxide compound diethyl {[(5-[2-(diethoxyphosphoryl)acetamido]-3-{2-[2-(diethoxyphosphoryl)acetamido]ethyl}pentyl)carbamoyl]methyl}phosphonate, C₂₅H₅₂N₃O₁₂P₃, features six intramolecular hydrogen-bonding interactions. The phosphonate groups have key bond lengths ranging from 1.4696 (12) to 1.4729 (12) Å (P=O), 1.5681 (11) to 1.5811 (12) Å (P—O) and 1.7881 (16) to 1.7936 (16) Å (P—C). Each amide group adopts a nearly perfecttransgeometry, and the geometry around each phophorus atom resembles a slightly distorted tetrahedron. 

Four β-carbonylphosphine oxide compounds were complexed with four Ln(NO₃)₃salts (Ln = Sm, Eu, Tb, Dy). The Ln–ligand complexes were characterized in the solid state (IR, CHN) and as solutions in acetonitrile (NMR, LR-MS, photophysical properties). 

The molecular structure of tert -butyl 3,6-diiodocarbazole-9-carboxylate, C 17 H 15 I 2 NO 2 , features a nearly planar 13-membered carbazole ring with C—I bond lengths of 2.092 (4) and 2.104 (4) Å. The carbamate group has key bond lengths of 1.404 (6) Å (N—C), 1.330 (5) Å (O—C), and 1.201 (6) Å (C=O). The crystal contains intermolecular π–π interactions, as well as both type I and type II intermolecular I...I interactions. 

This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis -1,2-bis(diphenylphosphanyl)ethylene, namely, 1,2-(ethene-1,2-diyl)bis(diphenylphoshpine sulfide/selenide), C 26 H 22 P 2 S 1.13 Se 0.87 . A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between F obs 2 and F calc 2 , plots of | F obs | vs | F calc |, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of interatomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures.