A decanuclear dysprosium phosphonate (I) undergoes two consecutive SC–SC transformations, associated with OFF–ON–OFF switching of its single-molecule-magnetism.

Two 1D coordination polymers composed of DyZn(salen) units and pyridin- N-oxide-4-carboxylate have been prepared by solvothermal reactions. Complex 1 with the formula {[DyZn(L)(POC)](OH)(ClO)}·HO·MeOH [HL] = N, N'-bis(3-methoxysalicylidene)-1,3-diaminopropane, POC = pyridin- N-oxide-4-carboxylate] is composed of a zigzag chain cation [DyZn(L)(POC)] as well as isolated hydroxide and perchlorate anions. Complex 2 with the formula {[DyZn(L)(POC)](OH)(ClO)}·9HO [HL] = N, N'-bis(3-methoxysalicylidene)-1,2-diaminoethane] is also an ionic compound containing isolated hydroxide and perchlorate anions, but its cation shows a novel nanowire structure, in which six-coordinate zinc(II) ions with C symmetry act as the axis and [DyZn(L)(POC)] structural units as spiral leaves. Complex 1 shows good single-molecule magnet performance with an U/ k value of 235.3(3.1) K ( H = 0 Oe), one of the largest values for coordination polymers. A butterfly-shaped magnetic hysteresis loop can be monitored at as high as 3.8 K for 1, while a dc field is necessary for complex 2 to display slow magnet relaxation owing to the quantum-tunneling effect, with a much smaller U/ k value of 14.6(0.2) K ( H = 1000 Oe). The difference of magnetic properties has been explained using detailed ab initio calculations.