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

A plot of χT vs. T is an important tool for determining the dominant interactions at
work in a magnetic system. Figure 1-1 depicts a generic plot of χT vs. T with three
potential scenarios. If ferromagnetic coupling (J > 0) is present then the χT product will
increase as the temperature is lowered, whereas if antiferromagnetic coupling (J < 0)
occurs then this value will decrease with a decrease in T. Also shown in this diagram is
ideal Curie behaviour (J = 0). In this situation the χT product will be unchanged across
the entire temperature regime and will have a value related to the total spin of the system
according to the specific mathematical relationships discussed.
And so it follows equation 1.7 that the χT is defined by:
(1.8)
The Landé constant g tends to be very close to 2 for organic species and other types
of species which do not possess substantial magnetoanisotropy and so this equation can
be simplified to the approximation:
(1.9)
which allows a quick check for the value of χT one would expect for a molecular
system based on the ground state spin. For example if the you were dealing with a simple
organic radical with S = ½ then, plugging that value into equation 1.8 would give a value
for χT at 1.73 μ B or 0.375 cm 3 K mol -1 . For more on molecular magnetism see Olivier
Kahn’s work, Molecular Magnetism. 1
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