Guest-induced magnetic exchange in paramagnetic [M2L4]4+ coordination cages

Mukesh Singh, Alvaro Etcheverry-berríos, Julia Vallejo, Sergio Sanz, José Martínez-lillo, Gary Stephen Nichol, Paul Lusby, Euan K Brechin

Research output: Contribution to journalArticlepeer-review

Abstract

Paramagnetic complexes that show magnetically switchable properties show promise in a number of applications. A significantly underdeveloped approach is the use of metallocages, whose magnetic properties can be modulated through host-guest chemistry. Here we show such an example that utilises a simple [CuII2L4]4+ lantern complex. Magnetic susceptibility and magnetisation data shows an absense of exchange in the presence of the diamagnetic guest triflate. However, replacement of the bound triflate by ReBr62- switches on antiferomagnetic exchange between the Cu and Re ions, leading to an S = 1/2 ground state for the non-covalent complex [ReBr62-⸦CuII2L4]2+. Comparison of this complex to a “control” palladium-cage host-guest complex, [ReBr62-⸦PdII2L4]2+, shows that the encapsulated ReBr62- anions retain the same magnetic anisotropy as in the free salt. Theoretically calculated spin-Hamiltonian parameters are in close agreement with experiment. Spin density analysis shows the mode of interaction between the CuII and ReIV centres is through the Re-Br···Cu pathway, primarily mediated through the Cu(dx2-y2)|Brsp|Re(dyz) interaction. This is further supported by overlap integral calculations between singly occupied molecular orbitals (SOMOs) of the paramagnetic ions and natural bonding orbitals analysis where considerable donor-to-acceptor interactions are observed between hybrid 4s4p orbitals of the Br ions and the empty 4s and 4p orbitals of the Cu ions.
Original languageEnglish
JournalDalton Transactions
Early online date10 May 2022
DOIs
Publication statusE-pub ahead of print - 10 May 2022

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