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Synthetic diversity and change in nuclearity in [Co–Dy] coordination aggregates: bridge removal, solvent induced structural reorganization and AC susceptibility measurements

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Abstract

Three new cobalt(II/III)-dysprosium(III) complexes, [DyIII3CoII2CoIII2(L1)2(O2CCMe3)8(OH)4(OMe)2(H2O)4]·Dy(η1-O2CCMe3)22-O2CCMe3)2(MeOH)2·4H2O (1), [DyIII3CoII2CoIII2(L2)2(O2CCMe3)8(OH)4(OMe)2(MeOH)2(H2O)2]·Dy(η1-O2CCMe3)22-O2CCMe3)2(MeOH)2·4MeOH (2) and DyIII2CoII2CoIII2(L2)2(O2CCMe3)10(OH)2 (3) have been reported. In the heptanuclear 3d–4f monocationic aggregates in 1 and 2 the three dysprosium and four cobalt sites are arranged into a vertex shared dicubane structure, induced by two structure-directing ligands. Interestingly, a unique and previously unknown dysprosium(III)-pivalate based counter anion, Dy(η1-O2CCMe3)22-O2CCMe3)2(MeOH)2, was trapped by the monocationic cores during crystallization. MeCN induced structural rearrangement of 2 through loss of OMe bridges and dysprosium(III) ions at the shared vertex resulted in the hexanuclear 3d–4f neutral aggregate 3, in which two dysprosium and four cobalt sites exhibit a near planar disposition. HRMS(+ve) of solutions of 1 and 2 revealed the pathway for aggregation processes and solvent induced structural transformation along with the importance of bridging OMe in directing the formation of these compounds. Magnetic studies show a non-zero out-of-phase component in the AC susceptibility measurements of 1 but not in 2 and 3, although 1 and 2 have a very similar {CoIII2CoII2DyIII3} core and another DyIII center. Ab initio single-ion calculations point to the different single-ion anisotropic behavior for DyIII centers (energy in cm−1 and g-tensors) as well as negative and positive D values for CoII sites in 1 and 2 respectively reaffirming the experimental result. However, calculations envision that, zero-field out-of-phase signal and no out-of-phase signal in 1 and 2 respectively do not solely generate from the single-ion Dy/Co anisotropies and the overall relaxation mechanism can be understood by considering the exchange interactions between DyIII–DyIII and DyIII–CoII centres.

Graphical abstract: Synthetic diversity and change in nuclearity in [Co–Dy] coordination aggregates: bridge removal, solvent induced structural reorganization and AC susceptibility measurements

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Supplementary files

Article information


Submitted
13 May 2020
Accepted
21 May 2020
First published
21 May 2020

Dalton Trans., 2020, Advance Article
Article type
Paper

Synthetic diversity and change in nuclearity in [Co–Dy] coordination aggregates: bridge removal, solvent induced structural reorganization and AC susceptibility measurements

D. Basak, J. van Leusen, T. Gupta, P. Kögerler and D. Ray, Dalton Trans., 2020, Advance Article , DOI: 10.1039/D0DT01728K

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