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Reversible Spin-State Switching and Tuning of Nuclearity and Dimensionality via Nonlinear Pseudohalides in Cobalt(II) Complexes

Abstract : The self-assembly of a macrocyclic tetradentate ligand, cobalt(II) tetrafluoroborate, and nonlinear pseudohalides (dicyanamide and tricyanomethanide) has led to two cobalt(II) complexes, {[Co(L)(μ 1,5-dca)](BF 4)•MeOH} n (1) and [Co 2 (L) 2 (μ 1,5-tcm) 2 ](BF 4) 2 (2) (L = N,N′-di-tert-butyl-2,11diaza[3,3](2,6)pyridinophane; dca − = dicyanamido; tcm − = tricyanomethanido). Both complexes were characterized by single-crystal X-ray diffraction, spectroscopic, magnetic, and electrochemical studies. Structural analyses revealed that 1 displays a one-dimensional (1D) coordination polymer containing [Co-(L)] 2+ repeating units bridged by μ 1,5-dicyanamido groups in cis positions, while 2 represents a discreate dinuclear cobalt(II) molecule bridged by two μ 1,5-tricyanomethanido groups in a cis conformation. Both complexes have a CoN 6 coordination environment around each cobalt center offered by the tetradentate ligand and cis coordinating bridging ligands. Complex 1 exhibits a high-spin (S = 3/2) state of cobalt(II) in the temperature range of 2−300 K with a weak ferromagnetic coupling between two dicyanamido-bridged cobalt(II) centers. Interestingly, complex 2 exhibits reversible spin-state switching associated with spin−spin coupling. Complexes 1 and 2 also exhibit interesting redox-stimuli-based reversible paramagnetic high-spin cobalt(II) to diamagnetic low-spin cobalt(III) conversion, offering an additional way to switch magnetic properties. A detailed theoretical calculation was consistent with the stated results.
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Submitted on : Thursday, January 14, 2021 - 2:05:34 PM
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Subrata Ghosh, Sujit Kamilya, Mathieu Rouzières, Radovan Herchel, Sakshi Mehta, et al.. Reversible Spin-State Switching and Tuning of Nuclearity and Dimensionality via Nonlinear Pseudohalides in Cobalt(II) Complexes. Inorganic Chemistry, American Chemical Society, 2020, 59 (23), pp.17638-17649. ⟨10.1021/acs.inorgchem.0c02887⟩. ⟨hal-03110216⟩



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