2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, a hydrogen-bonded organic quasi-1D ferromagnet


Autoria(s): MURATA, Hidenori; MIYAZAKI, Yuji; INABA, Akira; Paduan Filho, Armando; Bindilatti, Valdir; Oliveira Junior, Nei Fernandes de; DELEN, Zeynep; LAHTI, Paul M.
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

20/10/2012

20/10/2012

2008

Resumo

The title radical (F4BlmNN) is a stable nitronylnitroxide that forms hydrogen-bonded NH center dot center dot center dot ON chains in the solid state. The chains assemble the F4BlmNN molecules to form stacked contacts between the radical groups, in a geometry that is expected to exhibit ferromagnetic (FM) exchange based on spin polarization (SP) models. The experimental magnetic susceptibility of F4BlmNN confirms the expectation, showing 1-D Heisenberg chain FM exchange behavior over 1.8-300 K with an intrachain exchange constant Of J(chain)/k = +22 K. At lower temperatures, ac magnetic susceptibility and variable field heat capacity measurements show that F4BlmNN acts as a quasi-1-D ferromagnet. The dominant ferromagnetic exchange interaction is attributable to overlap between spin orbitals of molecules within the hydrogen-bonded chains, consistent with the SP model expectations. The chains appear to be antiferromagnetically exchange coupled, giving cusps in the ac susceptibility and zero field heat capacity at lower temperatures. The results indicate that the sample orders magnetically at about 0.7 K. The magnetic heat capacity ordering cusp shifts to lower temperatures as external magnetic field increases, consistent with forming a bulk antiferromagnetic phase below a Neel temperature of T-N(0) = 0.72 K, with a critical field of H-c approximate to 1800 Oe. The interchain exchange is estimated to be zJ/k congruent to (-)0.1 K.

Identificador

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, v.130, n.1, p.186-194, 2008

0002-7863

http://producao.usp.br/handle/BDPI/29330

10.1021/ja074211g

http://dx.doi.org/10.1021/ja074211g

Idioma(s)

eng

Publicador

AMER CHEMICAL SOC

Relação

Journal of the American Chemical Society

Direitos

restrictedAccess

Copyright AMER CHEMICAL SOC

Palavras-Chave #TEMPERATURE HEAT-CAPACITIES #MOLECULAR MAGNETIC-MATERIALS #NITRONYL NITROXIDE CRYSTAL #FREE-RADICAL MAGNET #PHASE-DIAGRAM #TRANSITION #DERIVATIVES #PROPERTY #EXCHANGE #DENSITY #Chemistry, Multidisciplinary
Tipo

article

original article

publishedVersion