Magnetic Tuning of All-Organic Binary Alloys between Two Stable Radicals

Autor(es)

Seber, Gonca ^[1] ; Freitas, Rafael S. ^[2] ; Mague, Joel T. ^[3] ; Paduan-Filho, Armando ^[2] ; Gratens, Xavier ^[2] ; Bindilatti, Valdir ^[2] ; Oliveira, Jr., Nei Fernandes ^[2] ; Yoshioka, Naoki ^[4] ; Lahti, Paul M. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Massachusetts, Dept Chem, Amherst, MA 01003 - USA

^[2] Univ Sao Paulo, Inst Fis, BR-05314970 Sao Paulo - Brazil

^[3] Tulane Univ, Dept Chem, New Orleans, LA 70118 - USA

^[4] Keio Univ, Dept Appl Chem, Yokohama, Kanagawa 2238522 - Japan

• Tipo de documento: Artigo Científico
• Fonte: Journal of the American Chemical Society; v. 134, n. 8, p. 3825-3833, FEB 29 2012.
• Citações Web of Science: 17

Resumo

Mixtures of 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro -1H-imidazole-3-oxide-1-oxyl (F4BImNN) and 2-(benzi-midazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-ox ide-1-oxyl (BImNN.) crystallize as solid solutions (alloys) across a wide range of binary compositions. (F4BImNN)(x)(BImNN)((1-x)) with x < 0.8 gives orthorhombic unit cells, while x >= 0.9 gives monoclinic unit cells. In all crystalline samples, the dominant intermolecular packing is controlled by one-dimensional (1D) hydrogen-bonded chains that lead to quasi-1D ferromagnetic behavior. Magnetic analysis over 0.4-300 K indicates ordering with strong 1D ferromagnetic exchange along the chains (J/k = 12-22 K). Interchain exchange is estimated to be 33- to 150-fold weaker, based on antiferromagnetic ordered phase formation below Neel temperatures in the 0.4-1.2 K range for the various compositions. The ordering temperatures of the orthorhombic samples increase linearly as (1 - x) increases from 0.25 to 1.00. The variation is attributed to increased interchain distance corresponding to decreased interchain exchange, when more F4BImNN is added into the orthorhombic lattice. The monoclinic samples are not part of the same trend, due to the different interchain arrangement associated with the phase change. (AU)

• Processo FAPESP: 07/50968-0 - Pesquisa em novos materiais envolvendo campos magnéticos intensos e baixas temperaturas
• Beneficiário: Nei Fernandes de Oliveira Junior
• Modalidade de apoio: Auxílio à Pesquisa - Temático