LANGMUIR-BLODGETT-FILMS OF SPIN TRANSITION IRON(II) METALLOORGANIC POLYMERS .1. IRON(II) COMPLEXES OF OCTADECYL-1,2,4-TRIAZOLE

A series of iron(II) metalloorganic polymers of 4-octadecyl-1,2,4-triazole has been synthesized. Their spin transition properties have been checked by Mossbauer spectroscopy, by magnetic susceptibility measurements, and particularly by IR spectroscopy, which was shown to be an easy and sensitive way to characterize spin transition phenomena. Counteranion exchange was used to tune the spin transition temperature. The compound with tosylate counterions was found to present a sharp transition close to room temperature. Comparison between polymers of 4-octadecyl-1,2,4-triazole and 4-amino-1,2,4-triazole showed that the cooperativity process in those compounds is mainly intramolecular, i.e., between Fe-II centers of the same polymer chain. The iron(II) amphiphilic compounds were unstable at the air-water interface and direct fabrication of langmuir-Blodgett films was not achieved. Diffusion of iron(II) salts into Langmuir-Blodgett films of 4-octadecyl-1,2,4-triazole led to complexes with polymer chains that were too short to present spin transition properties.