One of the most challenging aspects of synthesizing magnetic materials with the desired properties is the fine geometric control of the molecules that is required. For example, when superexchange pathways are involved, changes in the angle and degree of magnetic orbital overlap can switch the preferred magnetic ordering of a molecule from ferromagnetic ordering to antiferromagnetic ordering. In contrast, if a direct exchange pathway through a ligand with one unpaired electron is used the coupling between metal centers should be ferromagnetic regardless of the exchange pathway geometry.One method we are pursuing to take advantage of the direct exchange pathway is to use the tetrazine-based ligand bmtz (bmtz = 3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine) to link paramagnetic metal centers. Bmtz is known to be stable as a radical anion, both in the free ligand form and when complexed to transition metals. Our current focus is to synthesize new dinuclear complexes with neutral bmtz and then use a reducing agent to post-synthetically generate the ligand radical. These model compounds can then be used to study the effectiveness of bmtz at coupling magnetic moments in both the neutral and radical forms. Preliminary results for the radical [((NiII(tren)2(bmtz))]3+ complex (Figure 1) demonstrate that the bmtz radical engenders very strong ferromagnetic exchange (J = +65 cm-1) between the NiIIions. 

Exploring the magnetic coupling capabilities of a tetrazine-based radical ligand

248th National Meeting (2014)

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