Exploiting host–guest chemistry to manipulate magnetic interactions in metallosupramolecular M4L6 tetrahedral cages

Aaron J. Scott, Julia Vallejo, Arup Sarkar, Lucy Smythe, E. Regincós Martí, Gary S. Nichol, Wim T. Klooster, Simon J. Coles, Mark Murrie, Gopalan Rajaraman, Stergios Piligkos, Paul J. Lusby, Euan K. Brechin

Research output: Contribution to journalArticlepeer-review

Abstract

Reaction of Ni(OTf)2 with the bisbidentate quaterpyridine ligand L results in the self-assembly of a tetrahedral, paramagnetic cage [NiII4L6]8+. By selectively exchanging the bound triflate from [OTf⊂NiII4L6](OTf)7 (1), we have been able to prepare a series of host–guest complexes that feature an encapsulated paramagnetic tetrahalometallate ion inside this paramagnetic host giving [MIIX4⊂NiII4L6](OTf)6, where MIIX42− = MnCl42− (2), CoCl42− (5), CoBr42− (6), NiCl42− (7), and CuBr42− (8) or [MIIIX4⊂NiII4L6](OTf)7, where MIIIX4− = FeCl4− (3) and FeBr4− (4). Triflate-to-tetrahalometallate exchange occurs in solution and can also be accomplished through single-crystal-to-single-crystal transformations. Host–guest complexes 1–8 all crystallise as homochiral racemates in monoclinic space groups, wherein the four {NiN6} vertexes within a single Ni4L6 unit possess the same Δ or Λ stereochemistry. Magnetic susceptibility and magnetisation data show that the magnetic exchange between metal ions in the host [NiII4] complex, and between the host and the MX4n− guest, are of comparable magnitude and antiferromagnetic in nature. Theoretically derived values for the magnetic exchange are in close agreement with experiment, revealing that large spin densities on the electronegative X-atoms of particular MX4n− guest molecules lead to stronger host–guest magnetic exchange interactions.
Original languageEnglish
Pages (from-to)5134-5142
JournalChemical Science
Volume2021
Issue number14
Early online date1 Mar 2021
DOIs
Publication statusE-pub ahead of print - 1 Mar 2021

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