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Interplay between the Supramolecular Motifs of Polypyridyl Metal Complexes and Halogen Bond Networks in Cocrystals

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journal contribution
posted on 03.02.2016, 00:00 by Michael C. Pfrunder, Aaron S. Micallef, Llewellyn Rintoul, Dennis P. Arnold, John McMurtrie
Combining [Ni­(phen)3]­I2 or [Ni­(phen)3]­Cl2 (phen = 1,10-phenanthroline) with the iodoperfluorobenzenes (IPFBs), 1,2-, 1,3-, 1,4-diiodotetrafluorobenzene (1,2-, 1,3-, and 1,4-DITFB, respectively), or 1,3,5-triiodotrifluorobenzene (1,3,5-TITFB) resulted in the formation of six different cocrystalline materials featuring halogen-bonded networks encapsulating [Ni­(phen)3]2+ ions. The cocrystals have the general formula [Ni­(phen)3]­[(IPFB)n(X2)­(L)m]·solvate (n = 2 or 3; X = Cl or I; L = halogen-bonded H2O and/or MeOH; solvate = isolated H2O and/or MeOH). The halide ions balance the charge of the metal complexes and simultaneously act as halogen bond acceptors for the electronically polarized iodine atoms of the IPFB donors. The structures display a wide variety of supramolecular motifs in the context of both the aggregation of the metal complexes and the topology and connectivity of the halogen bond networks. The well-known supramolecular “aryl embrace” motifs of [Ni­(phen)3] complexes are present but are structurally compromised to varying degrees in the crystals of [Ni­(phen)3]­[(1,2-DITFB)2I2]·MeOH, [Ni­(phen)3]­[(1,3-DITFB)2I2]·2MeOH, and [Ni­(phen)3]­[(1,3-DITFB)2(H2O)2Cl2]·1.5MeOH. In [Ni­(phen)3]­[(1,3-DITFB)3I2], the [Ni­(phen3]2+ complexes are so thoroughly enclosed in halogen-bonded networks that the metal complexes have no significant supramolecular contact. In contrast, in [Ni­(phen)3]­[(1,4-DITFB)3I2(MeOH)0.5] and [Ni­(phen)3]­[(1,3,5-TITFB)2Cl2] the complexes are arranged in typical aryl embrace motifs (pairwise and 1D chains, respectively), but with adjacent complexes held in closer proximity to each other than they reside in crystals of the pure metal complex. The interplay between the supramolecular chemistry of the halogen-bonded networks and the metal complexes was examined in detail, and the results demonstrate that it is possible to significantly influence the aggregation of metal complexes by encapsulation in different halogen bond networks.

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