Triazole-based magnetic Langmuir-Blodgett films:: Paramagnetic to spin-crossover behavior

The behavior at the air-liquid interface of a series of metal(II) metallo-organic polymers of 4-octadecyl-1,2,4-triazole has been studied. Interactions between those amphiphilic compounds and metal ions in the subphase result in the formation of stable monolayers and well-defined Langmuir-Blodgett (LB) films incorporating oligomeric metal(II)/triazole units. Infrared, X-ray Photoelectron Microscopy, and magnetic measurements show that the obtained LB films are mostly resulting from recoordination of metal ions from the subphase with triazole ligands at the air-water interface. The relative stability of the polymers and the efficiency of association with 4-octadecyl-1,2,4-triazole have been found to follow the Ni > Fe similar to Cu > Co and Cu > Ni > Fe > Co sequences, respectively. In the iron(II) cases, partial spin-crossovers are observed, demonstrating for the first time the feasibility of triazole-based LB films possessing interesting magnetooptical properties.