Manipulating the crystal packing of pyDTDA radical ligand coordination complexes with Mn(ii) and Ni(ii).

The synthesis of 4'-CN, 5'-CN and 5'-Br substituted pyDTDA neutral radical bidentate ligands is reported (pyDTDA = 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl). The Ni(hfac)(2) and Mn(hfac)(2) coordination complexes of both cyano substituted ligands, and the Mn(hfac)(2) coordination complex of the bromo substituted ligand, have been prepared and the crystal packing of these is compared (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-). Unlike the previously reported Mn(hfac)(2)(pyDTDA), the Mn(hfac)(2)(4'-CN-pyDTDA) complex does not form dimers in the solid-state making it possible to measure the magnetic coupling between the unpaired electrons on the coordinated Mn(ii) ion and the unpaired electron on the radical ligand by SQUID magnetometry; J/k(B) = -74(1) K, using H = -2J{S(Mn).S(Rad)} and g(av.) = 2.01.