Single-Molecule Magnet Behavior of 1D Coordination Polymers Based on DyZn2(salen)2 Units and Pyridin- N-Oxide-4-Carboxylate: Structural Divergence and Magnetic Regulation.

Two 1D coordination polymers composed of DyZn2(salen)2 units and pyridin- N-oxide-4-carboxylate have been prepared by solvothermal reactions. Complex 1 with the formula {[DyZn2(La)2(POC)](OH)(ClO4)}·H2O·MeOH [H2La] = N, N'-bis(3-methoxysalicylidene)-1,3-diaminopropane, POC- = pyridin- N-oxide-4-carboxylate] is composed of a zigzag chain cation [DyZn2(La)2(POC)] n2 n+ as well as isolated hydroxide and perchlorate anions. Complex 2 with the formula {[Dy3Zn7(Lb)6(POC)6](OH)3(ClO4)2}·9H2O [H2Lb] = 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 C3 symmetry act as the axis and [DyZn2(Lb)2(POC)]2+ structural units as spiral leaves. Complex 1 shows good single-molecule magnet performance with an Ueff/ k value of 235.3(3.1) K ( Hdc = 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 Ueff/ k value of 14.6(0.2) K ( Hdc = 1000 Oe). The difference of magnetic properties has been explained using detailed ab initio calculations.