Acta Cryst. (2013). B69, 43-54 [ doi:10.1107/S2052519212050439 ]
Abstract: The synthesis and characterization of a series of halogen-substituted pseudoterpyridine ZnII homoleptic mononuclear complexes, based on ligands L11-L44 [2,6-pyridinedicarboxaldehydebis(p-R-phenylimines), R = F, Cl, Br, I] are reported. Neither of the structures contain relatively strong classical hydrogen bonds (OHO, NHO, OHN, NHN) and the structure packing is thus determined by a subtle interplay of weaker interactions. Isostructurality of the four halogen analogues is very rare, and in this study -Br, -Cl and -F are found to be isostructural in different degrees, whereas -I is not. Interestingly, although it is closely isostructural to the -Cl and -Br compounds, the F analogue is shown not to form FO bonds, while the Cl and the Br analogues do form HalO bonds. This raises an important question on the role of HalO bonds in the structuration of the crystal packing, particularly the stabilization effect. Similarly, while the CHHal interaction seems to give one-dimensional cohesion in the -Cl and -Br analogues, this feature is absent in the -F analogue, despite its close isostructurality. CHO interactions appear to dominate to a first degree the cohesion between the anionic trifluoromethanesulfonate network and the cationic Zn-pyridinedicarboxaldehydebis(p-R-phenylimines) network. The analysis of these interactions is corroborated by reduced density gradient calculations based on promolecular densities.
Keywords: metallosupramolecular complexes; imine; self-assembly; weak hydrogen and halogen interactions.
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