1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

expected from one binuclear complex and 2 mononuclear complexes. As the temperature
is decreased at 1000 Oe the χT product decreases to a minimum value of 0.46 cm 3 K
mol -1 at 1.8 K. See Figure 2-12.
2.4 Discussion
The dimerization of the DSDA radical ligands in the nickel complex II-5 means that
the magnetic behaviour must arise entirely from the nickel ions interacting with one
another as indicated in scheme 2-4b. The magnetic data has been modeled on the basis of
an isotropic spin Heisenberg Hamiltonian:
(2.1)
where J is the magnetic interaction between the two nickel centers through the bridging
ligand and is the spin operator for the respective nickel ions. The theoretical
expression for the magnetic susceptibility in the weak-field approximation is: 2 (2.2)
A good agreement with the data is achieved down to 15 K using
= -4.3(5) K and
g av = 2.23(5). The good agreement between the model and the measurement confirms
that the radical ligand makes no contribution to the magnetic susceptibility. Importantly,
this complex is the only known example of these types of binuclear coordination species
that form dimers in the solid state despite the substantial steric bulk introduced by the
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