• In silico design of pseudo D5h actinide based molecular magnets: role of covalency in magnetic anisotropy

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    • Keywords

       

      Single-ion magnets; actinide magnets; magnetic anisotropy; CASSCF; QTM; Ueff.

    • Abstract

       

      Actinide molecular magnets are of great interest in the area molecular magnetism as they possess strong covalency and spin-orbit coupling that their 4f congeners lack. Despite these known advantages, the actinide based molecular magnets have not been explored in detail due to the limited availability of actinidesalts. While theoretical tools are proven to be useful in lanthanide chemistry towards prediction, they are still at an infant stage in actinide chemistry. In this manuscript, we have attempted to utilise CASSCF/RASSI-SO calculations to predict suitable pseudo D5h molecules possessing attractive magnetic properties. To begin with, we have undertaken an extensive benchmarking of the methodology employed by studying two sets of isostructural, [NdTp3], [UTp3], [Nd(COT²)2]-, [U(COT²)2]- {Tp- = trispyrazolylborate, COT² = bis(trimethylsilyl)cyclooctatetraenyl dianion} complexes. The method assessment reveals that the methodology employed is reliable as this has reproduced the experimental observables. With this, we have moved forward with prediction where pseudo-D5h symmetric [L2M(H2O)5][I]3L2.(H2O) {M = Nd, U, Pu; L =tBuPO(NHiPr)2} systems are modelled from their Nd(III) X-ray structure. Our calculations reveal that the Uranium complex studied possess superior SIM characteristics compared to its lanthanide analogue. Plutonium complex has prolate electron density at the ground state, and hence the ligand environment isunsuitable for yielding SIM behaviour. The role of solvent molecules, counter anions and equatorial and axial ligand are explored and tantalizing prediction with a barrier height of 1403.3 and 989.5 cm-1 are obtained for [tBuPO(NHiPr)2-U-tBuPO(NHiPr)2]3+ and [Pu(H2O)5]3+ models, respectively and this paves the way for synthetic chemist to target such geometries in actinide based SIMs.

    • Author Affiliations

       

      SOURAV DEY GOPALAN RAJARAMAN1

      1. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, Maharashtra, India
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