Double helical assembly of imino nitroxyl diradicals by silver(I) ions

The co-ordination of imino nitroxyl diradicals to diamagnetic silver(I) ion s led to the self-assembled double helical dimer [Ag-2(bisimpy)(2)][PF6](2) 1 (diradical bisimpy=2,6-bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-2 -yl 1-oxyl)pyridine). The diradical has two imino nitroxyl groups linked by the pyridine group at its meta positions and acts as a tridentate ligand. In the double helicate two bisimpy bridge two silver(I) ions in a {4+2} con nectivity, and the silver(I) ions have a very short contact of 2.8943(5) An gstrom. Magnetic susceptibility measurements and crystal structure analysis revealed that the two radical moieties in bisimpy are ferromagnetically co upled (J=17.4(8) cm(-1); H=2J Sigma S-i. S-j) through the pyridine group, a nd imino nitroxyl overlaps between adjacent molecules result in an intermol ecular antiferromagnetic interaction (-52.3(7) cm(-1)).