Metal Complexes of Bridging Neutral Radical Ligands: pymDTDA and pymDSDA

Metal complexes of the 4-(2′-pyrimidyl)-1,2,3,5-dithiadiazolyl
(pymDTDA) neutral radical ligand and its selenium analogue (pymDSDA)
are presented. The following series of metal ions has been studied
using M­(hfac)2 as the coordination fragment of choice (hfac
= 1,1,1,5,5,5-hexafluoroacetylacetonato): MnII, CoII, NiII, and ZnII. The binuclear cobalt
and nickel complexes of pymDTDA both exhibit ferromagnetic (FM) coupling
between the unpaired electrons on the ligand and the metal ion, while
the binuclear zinc complex of pymDTDA is presented as a comparative
example incorporating a diamagnetic metal ion. The binuclear manganese
complex of pymDTDA, reported in a preliminary communication, is compared
to the pymDSDA analogue, and new insight into the magnetic behavior
reveals that intermolecular magnetic coupling, mediated by chalcogen–oxygen
contacts, gives rise to a significant increase in the χT product at low temperature. Surprisingly, the binuclear
nickel complex of pymDSDA forms dimers in the solid state, as do the
mononuclear complexes of cobalt and nickel with pymDTDA. In addition,
mixed mononuclear/binuclear complexes of Mn- and Zn­(pymDTDA) have
been identified.