1,2,3-Dithiazolyl and 1,2,3,5-Dithiadiazolyl Radicals as Spin-Bearing Ligands Towards the Design of New Molecular Materials
A series of binuclear coordination complexes of 4-(2′-pyrimidal)-1,2,3,5-dithiadiazolyl and its selenium analogue have been prepared to examine their structural and magnetic properties. The zinc(II) coordination complex is the first example of a DTDA radical ligand N-coordinated to a diamagnetic metal center. The magnetic properties reveal that it exhibits Curie behaviour and can be used as a benchmark to compare the analogous coordination complexes which possess paramagnetic metal ions. The nickel(II) coordination complex of the selenium containing radical pymDSDA was shown to dimerize in the solid state and is the only binuclear complex thus far that has done so. The manganese(II) complex of pymDSDA is by far the most interesting and is isomorphous to the DTDA analogue. For both complexes, one of the two molecules in the asymmetric unit form chains in the solid state joined by intermolecular contacts between a sulfur or selenium atom from the radical, and an oxygen atom coordinated to a neighbouring molecule. This feature gives rise to a ground state spin greater than that of an individual binuclear coordination complex. The radical ligand is however disordered in the solid state and so these random chain lengths are dependent on the orientation of the ligands in adjacent complexes. The 1,2,3-DTA species examined herein are related to the 4,5-dioxo-4,5-dihydronaphtho[1,2-d][1,2,3]dithiazolyl radical and the related protonated species 4-hydroxy-5H-naphtho[1,2-d][1,2,3]dithiazol-5-one. The proton from this latter compound has shown that it can be substituted with alkyl groups and this was achieved using acetyl chloride to place an acetyl group in this position. The above radical did not exhibit the strong donor properties required for metal coordination and preliminary investigations of the radical dianionic suggest that it is chemically irreversible by cyclic voltametry. The acetyl group unfortunately did not provide the chemically reversibility of interest although has established a potential route toward the substitution chemistry of this compound. The other 1,2,3-DTA compounds discussed herein are not complete, although the data acquired on the precursor compounds leading up to the radical will be discussed.