Optimizing disordered crystal structures

A mixed-crystal full-mol­ecule disorder situation is revisited in Parkin et al. [Acta Cryst. (2023), C79, 77–82]. A new inter­pretation of the data leads to the conclusion that the crystal structure is more likely to be a three-component superposition of enantiomers and the meso isomer of an organic compound and the article is thus a good learning example for dealing with a highly disordered structure.

Crystal structure and characterization of the sul­famethazine–pi­peri­dine salt

The pi­peri­dinium–sul­fa­methazinate salt was prepared by the solvent-assisted grinding method. The ions are connected by N—H⁺⋯O and N—H⁺⋯N inter­actions. The self-assembly of sul­fa­methazinate anions displays the amine–sulfa C(8) motif. The supra­molecular architecture of the salt revealed the formation of inter­connected supra­molecular sheets.

(E,E)-1,1′-[1,2-Bis(4-chloro­phen­yl)ethane-1,2-di­yl]bis­(phenyl­diazene) revisited: threefold configurational disorder of (S,S), (R,R) and (S,R) isomers, a detailed critique

A distorted structure originally described as a mono­clinic polymorph of meso-(E,E)-1,1′-[1,2-bis­(4-chloro­phen­yl)ethane-1,2-di­yl]bis­(phenyl­diazene) is better modeled as a threefold superposition of undistorted S,S and R,R enanti­omers with a smaller fraction of the meso isomer. All reasoning behind the reassessment is explained in detail.

Di­bromo­methyl- and bromo­methyl- or bromo-substituted ben­zenes and naph­tha­lenes: C—Br⋯Br inter­actions

The Br⋯Br inter­actions in the crystal structures of nine di­bromo­methyl-substituted ben­zenes and naph­tha­lenes play a crucial role in the crystal packing. The occurrence of Type I and Type II inter­actions is discussed considering the effective atomic radius of bromine, together with the impact on the packing of mol­ecules in the individual structures.

Conversion of 2-methyl-4-styryl­quino­lines into 2,4-distyryl­quino­lines: synthesis, and spectroscopic and structural characterization of five examples

Five new 4-(aryl­vin­yl)-2-styrylquino­lines have been synthesized using indium chloride-catalyzed condensation reactions between their 4-(aryl­vin­yl)-2-methyl- analogues and either mono- or diketones. The supra­molecular arrangements range from isolated mol­ecules via hy­dro­gen-bonded dimers and sheets to three-dimensional framework structures.

Synthesis and crystal structures of new chiral 3-amino-2H-azirines and the Pd com­plex of one of them

Three new 3-amino-2H-azirine derivatives have been synthesized as racemates or mixtures of diastereoisomers. Comparison of their crystal structures with those of the 11 other 3-amino-2H-azirines in the literature reveal that the formal N—C single bond in the azirine ring is consistently long at around 1.57 Å.