*2.2. Magnetic Behaviour*

Magnetic susceptibility (χM) data were measured on a powdered, restrained crystalline sample of **1** under a 0.1 T dc field in the T = 5–300 K temperature range. The temperature dependence of the χMT product is shown in Figure 6. At room temperature, the χMT value of 40.82 cm<sup>3</sup> K mol-<sup>1</sup> is close to the Curie constant expected for eight MnIII and four MnII ions, assuming a *g*-value of 2.00 (41.5 cm<sup>3</sup> K mol-1). The χMT value remains approximately constant as the temperature is decreased until ~150 K, where it starts to decrease, reaching a minimum value of 13.27 cm<sup>3</sup> K mol-<sup>1</sup> at 5 K. This behaviour is indicative of the presence of predominantly weak antiferromagnetic interactions between the constituent metal ions. A fit of the 1/χM versus T data to the Curie–Weiss law afforded the Weiss constant, θ = −10 K. Magnetization measurements, performed in fields between 0.5–7 T (Figure 7), are in agreemen<sup>t</sup> with this observation, showing M increasing in a near linear like fashion with H, indicative of the field-induced population of low-lying excited states with larger magnetic moments. Previous magneto-structural correlations in alkoxide-bridged MnIII dimers in which the JT axes are coparallel, as seen in the central [Mn10] planar core (Figure 4), predict borderline and weak ferro- or antiferromagnetic exchange interactions, as observed [28]. No signals were observed in ac susceptibility measurements for data collected in the T = 1.8–10 K temperature range in frequencies up to 1500 Hz.

**Figure 6.** Plot of χMT vs T (o) and 1/χM vs T () in the range T = 5–300 K in an applied field of 0.1 T. The red line is a fit of the Curie–Weiss law. See text for details.

**Figure 7.** Field dependence of the magnetization (M) measured in the range T = 2–7 K and H = 0.5–7.0 T.
