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Upon further cooling to 2 K, an abrupt increase of χMT to
2.16 emu mol−1 K subsequently occurs. The Curie–Weiss
fitting [χM = C/IJT − θ)] of the magnetic data in the tempera-
ture range of 2–300 K for 1 and 100–300 K for 2 gives C =
4.25 emu mol−1 K, θ = −22.69 K for 1 and C = 3.51 emu mol−1
K, θ = −21.75 K for 2, respectively. As known, the magnetic
behavior of high-spin CoII ions is fairly complicated and diffi-
cult to explain. Therefore, we suggest that the decrease of
χMT values at high temperatures should be attributed mainly
to the strong spin–orbital coupling of a single CoII ion, which
also contributes to the negative θ values.
Key Scientific Research Project of Colleges and Universities in
Henan Province (15A150032) and Pingdingshan Key Scientific
Research Project (2013066).
Notes and references
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To better understand the magnetic behaviors of 1 and 2,
the strength of AF exchange interactions caused by spin–orbit
coupling of the CoII ions was estimated using eqn (1).16
χMT = A exp(−E1/kT) + B exp(−E2/kT)
(1)
In eqn (1), the sum of parameters A and B equals to the
Curie constant, while E1 and E2 refer to the spin–orbit cou-
pling constant and activation energy of F/AF interactions,
respectively. The best fit of experimental data (Fig. 6) gives A
+ B = 4.30 emu mol−1 K, −E1/k = −45.59 K and −E2/k = −4.44 K
for 1, and A + B = 3.48 emu mol−1 K, −E1/k = −51.87 K and
−E2/k = −0.18 K for 2. The negative value of −E2/k for both 1
and 2 further indicates the dominant AF interactions in 1
and weak canted AF interactions in 2.
To further confirm the canted AF coupling between the
CoII ions of 2, isothermal field-dependent magnetization
MIJH) has also been investigated (see the inset of Fig. 6b).
Upon increasing the field strength, magnetization increases
fast at low fields and slowly at high fields, and ultimately
approximates to 2.38 Nβ at 50 kOe, which strongly supports
the canted antiferromagnetism in 2.
According to the literature, the syn–anti-μ2-η1:η1 bridging
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magnetism.16 However, 1 and 2 both consisting of 1D CoII
chains bridged via carboxylate groups in a syn–anti mode dis-
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Conclusions
Five CoII/ZnII CPs have been prepared based on H2tdzdc and
four N/O-donor auxiliary ligands. Structural analyses reveal a
significant dependence of the assembly structure on auxiliary
ligands. The distinct topological networks as well as the differ-
ent interpenetration degrees are observed in these CPs, which
can be interpreted reasonably in terms of the different sizes
and flexibilities of auxiliary ligands. In addition, magnetic
investigations reveal the AF and canted AF behaviors of 1 and
2, respectively, even though the CoII ions in them are both
bridged by carboxylate groups in similar coordination modes.
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Acknowledgements
This work was supported by the NSFC (21421001, 21403116,
and 21403102), MOE Innovation Team (IRT13022) of China,
This journal is © The Royal Society of Chemistry 2015
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