Lattice Solvent Engineering Improves the Stability of a Cobalt Pyrenylnitronylnitroxide Ferrimagnetic Chain

Rafael A Allão Cassaro; Paul M Lahti; Maria G F Vaz; Miguel A Novak

doi:10.1021/acs.inorgchem.3c01543

Lattice Solvent Engineering Improves the Stability of a Cobalt Pyrenylnitronylnitroxide Ferrimagnetic Chain

Inorg Chem. 2023 Jul 17;62(28):11248-11255. doi: 10.1021/acs.inorgchem.3c01543. Epub 2023 Jul 6.

Authors

Rafael A Allão Cassaro¹, Paul M Lahti², Maria G F Vaz³, Miguel A Novak⁴

Affiliations

¹ Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil.
² Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States.
³ Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24020-150, Brazil.
⁴ Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-972, Brazil.

PMID: 37411011
DOI: 10.1021/acs.inorgchem.3c01543

Abstract

Reaction of 2-(1'-pyrenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (PyrNN) with [Co(hfac)₂(H₂O)₂] (hfac = hexafluoroacetylacetonate) in n-heptane solvent (hep) with a small amount of bromoform (CHBr₃ = bf) gives the 1D ferrimagnetic complex [Co(hfac)₂PyrNN]_n·0.5bf·0.5hep (Co-PyrNN·bf). This chain exhibits slow magnetic relaxation with magnetic blocking below 13.4 K, presenting a magnetic hysteresis with high coercive field (51 kOe at 5.0 K) as a hard magnet. It also shows frequency-dependent behavior consistent with one dominant relaxation process with an activation barrier of Δ_τ/k_B = (365 ± 24) K. The compound is an isomorphous variant of a previously reported ambient unstable chain made by using chloroform (CHCl₃ = cf), [Co(hfac)₂PyrNN]_n·0.5cf·0.5hep (Co-PyrNN·cf). This shows that the variation of a magnetically inactive lattice solvent can improve the stability of analogous, void space containing single-chain magnets.