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A computational and crystallographic study of halogen···pi interactions in selected Co(II) and Ni(II) b-diketonates

With the increasing research on halogen bonds and their potential in crystal engineering the interest in other supramolecular interactions involving halogen atoms and their potential use has increased as well. A CSD study shows that halogen···pi interactions, although relatively weak, show high directionality and could be responsible for the crystal packing in some organic systems. The term halogen···pi interactions could be misleading as well since it includes two distinct types of interactions, sigma-hole···pi interactions with electron rich pi systems and X···pi-hole interactions with electron deficient pi systems. The nature of these types of interactions as well as their impact on the crystal packing remains to be further studied. We have prepared a series of Co(II) and Ni(II) pentane-2, 4-dionato complexes with a series of halo-pyridines/pyrazines/pyrimidines where interactions between the halogen atom and pi system have been observed. The study of geometrical parameters indicates that they should be X···pi-hole interactions however DFT calculations indicate that the pi-hole is not present in pyridine derivatives.

crystal engineering ; halogen bonds ; halogen···pi interactions ; Co(II) ; Ni(II) ; pentane-2, 4-dionato complexes ; halo-pyridines ; halo-pyrazines ; halo-pyrimidines ; DFT

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