[MIII2MII3]n+ trigonal bipyramidal cages based on diamagnetic and paramagnetic metalloligands.

Sergio Sanz, Helen M. O'Connor, Vicente Martí-centelles, Priyanka Comar, Mateusz Pitak, Simon Coles, Giulia Lorusso, Elias Palacios, Marco Evangelisti, Amgalanbaatar Baldansuren, Nicholas F Chilton, Høgni Weihe, Eric J L Mcinnes, Paul Lusby, Stergios Piligkos, Euan K. Brechin

Research output: Contribution to journalArticlepeer-review

Abstract

A family of five [MIII2MII3]n+ trigonal bipyramidal cages (MIII = Fe, Cr and Al; MII = Co, Zn and Pd; n = 0 for 1-3 and n = 6 for 4-5) of formulae [Fe2Co3L6Cl6] (1), [Fe2Zn3L6Br6] (2), [Cr2Zn3L6Br6] (3), [Cr2Pd3L6(dppp)3](OTf)6 (4) and [Al2Pd3L6(dppp)3](OTf)6 (5) (where HL is 1-(4-pyridyl)butane-1,3-dione and dppp is 1,3-bis(diphenylphosphino)propane) are reported. Neutral cages 1-3 were synthesised using the tritopic [MIIIL3] metalloligand in combination with the salts CoIICl2 and ZnIIBr2, which both act as tetrahedral linkers. The assembly of the cis-protected [PdII(dppp)(OTf)2] with [MIIIL3] afforded the anionic cages 4-5 of general formula [MIII2PdII3](OTf)6. The metallic skeleton of all cages describes a trigonal bipyramid with the MIII ions occupying the two axial sites and the MII ions sitting in the three equitorial positions. Direct current (DC) magnetic susceptibility, magnetisation and heat capacity measurements on 1 reveal weak antiferromagnetic exchange between the FeIII and CoII ions. EPR spectroscopy demonstrates that the distortion imposed on the {MO6} coordination sphere of [MIIIL3] by complexation in the {MIII2MII3} supramolecules results in a small, but measurable, increase of the zero field splitting at MIII. Complete active space self-consistent field (CASSCF) calculations on the three unique CoII sites of 1 suggest DCo ≈ -14 cm-1 and E/D ≈ 0.1, consistent with the magnetothermal and spectroscopic data.
Original languageEnglish
JournalChemical Science
Early online date19 May 2017
DOIs
Publication statusE-pub ahead of print - 19 May 2017

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