engleski

N-(4-halogeno)benzyl-(3-halogeno)pyridinium cations as asymmetric ditopic halogen bond donors

Halogen bond is a valuable widely used tool for constructing supramolecular assemblies in the solid state. To date, neutral molecules have been highlighted as the most common halogen bond donors. Besides numerous studies on neutral halogen bond donors, a few studies dealing with cationic halogen bond donors such as halogenopyridinium cations have been published. In our previous work we have shown that halogen bonds in protonated iodopyridinium halogenides can even compete with hydrogen bond in binding halogenide anions. In this study, we have been interested in asymmetric cationic ditopic halogen bond donor where one halogen bond donor atom is placed on positively charged pyridine ring while other one on “neutral” benzyl ring (the positive charge is mostly located on the pyridine nitrogen ring). We successfully prepared a series of four N-(4- halogeno)benzyl-(3- halogeno)pyridinium bromides. In order to study the halogen bonding potential of this cations with a wider range of (anionic) halogen bond acceptors the chloride and iodide salts were prepared by ion exchange. Single crystal X-ray diffraction experiments revealed that in these systems halogen bonds with the halogen atoms on pyridinium rings with halogenide anions are generally relatively shorter (as compared to the corresponding van der Waals radii) than the halogen bonds with the halogen atoms on the “neutral” part of cations (benzyl ring).

halogen bond donor ; halogenopyridinium cation

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