Halogen Bond-Assisted Supramolecular Dimerization of Pyridinium-Fused 1,2,4-Selenadiazoles via Four-Center SeN Chalcogen Bonding.

The synthesis and structural characterization of α-haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles with various counterions is reported herein, demonstrating a strategy for directed supramolecular dimerization in the solid state. The compounds were obtained through a recently discovered 1,3-dipolar cycloaddition reaction between nitriles and bifunctional 2-pyridylselenyl reagents, and their structures were confirmed by the X-ray crystallography. α-Haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles exclusively formed supramolecular dimers via four-center Se···N chalcogen bonding, supported by additional halogen bonding involving α-haloalkyl substituents.

Crystal structure and Hirshfeld surface analysis of 4-(2-chloro-eth-yl)-5-methyl-1,2-di-hydro-pyrazol-3-one.

In the crystal of the title compound, CHClNO, mol-ecular pairs form dimers with an (8) motif through N-H⋯O hydrogen bonds. These dimers are connect into ribbons parallel to the (100) plane with (10) motifs by N-H⋯O hydrogen bonds along the axis direction. In addition, π-π [centroid-to-centroid distance = 3.