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Strong Antiferromagnetic Coupling of Spins in the (MDABCO + )(C 60 .− ) Salt with 3D Close Packing of the C 60 .− Radical Anions (MDABCO + : N ‐Methyldiazabicyclooctanium Cation)
Author(s) -
Konarev Dmitri V.,
Khasanov Salavat S.,
Otsuka Akihiro,
Yamochi Hideki,
Saito Gunzi,
Lyubovskaya Rimma N.
Publication year - 2014
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201402048
Subject(s) - antiferromagnetism , fullerene , spins , crystallography , van der waals force , center (category theory) , chemistry , coupling (piping) , magnetic susceptibility , condensed matter physics , materials science , physics , molecule , organic chemistry , metallurgy
A new salt, (MDABCO + )(C 60 .− ) ( 1 ; MDABCO + = N ‐methyldiazabicyclooctanium cation), was obtained as single crystals. The crystal structure of 1 determined at 250 and 100 K showed 3D close packing of fullerenes with eight fullerene neighbors for each C 60 .− . These neighbors are located at 10.01–10.11 Å center‐to‐center distances (250 K) and van der Waals interfullerene C⋅⋅⋅C contacts are formed with four fullerene neighbors arranged in the bc plane. Fullerene ordering observed below 160 K is accompanied by the appearance of one and a half independent C 60 .− and trebling of the unit cell along the b axis. Fullerenes are packed closer to each other at 100 K. As a result, fullerenes are located in the three‐dimensional packing at 9.91–10.12 Å center‐to‐center distances and 18 short interfullerene C⋅⋅⋅C contacts are formed for each C 60 .− . Although they are closed packed, fullerenes are not dimerized down to 1.9 K. Magnetic data indicate strong antiferromagnetic coupling of spins in the 70–300 K range with a Weiss temperature of Θ =−118 K. Magnetic susceptibility shows a round maximum at 46 K. Such behavior can be described well by the Heisenberg model for square two‐dimensional antiferromagnetic coupling of spins with an exchange interaction of J / k B =−25.3 K. This magnetic coupling is one of the strongest observed for C 60 .− salts.