A strategy for obtaining isostructurality despite structural diversity in coordination compounds.

To investigate the effect of conformationally flexible molecules on the crystal packing of coordination compounds, eleven mercury(II) complexes containing N-(3-halophenyl)-2-pyridinecarboxamide ligands, carrying different halogen atoms in the ortho-position of the phenyl ring, have been synthesized, molecularly characterized and structurally compared. In this contribution, three various sets of isostructural compounds were obtained by manipulating the proportions of the different solvents and the crystallization temperatures. By varying the reaction conditions three different compositions were observed, and from each composition, independent isostructural series could be observed by halogen replacements. Due to the simultaneous presence of competitive halogen atoms and the flexibility of ligands, conformational preference and altering the kind of halo-atom of ligands can change the nature and type of intermolecular interactions. Despite the presence of isostructurality in the studied compounds, structural diversity is also observed. The structural similarities of these isostructural compounds were interpreted via Hirshfeld surface fingerprint plots, Xpac, and unit cell similarity comparison. Synthon crossover of halogen interaction in coordination compounds of HgX₂ was observed, and systematic investigation of halogen⋯halogen interactions utilizing energy calculation was performed. Halogen⋯halogen synthon crossover in coordination compounds has been investigated. [ABSTRACT FROM AUTHOR]