Urethane cross-linked poly(oxyethylene)/siliceous nanohybrids doped with Eu3+ ions -: Part 2.: Ionic association

Fourier transform mid-IR and Raman spectroscopies were employed to investigate the anionic local surrounding in sol-gel derived organic/inorganic materials - monourethanesils - incorporating europium triflate, Eu(CF3SO3)(3). The hybrid framework of these xerogels contains short methyl end capped polyether segments grafted to a siliceous network through urethane cross-links. Samples with compositions infinity > n greater than or equal to 10 (where n indicates the ratio of (OCH2CH2) moieties per lanthanide ion) were examined. The spectral data obtained provide conclusive evidence of the presence of "free'' and weakly coordinated CF3SO3- ions located in two distinct sites in the whole range of salt concentration analyzed. At n = 30 and 10, along with these species, two new anionic configurations, assigned to contact ion pairs and "cross-link separated'' ions pairs, emerge. Two-dimensional correlation spectroscopic analysis allowed to clarify the number of components present in two critical bands containing strongly overlapped spectral profiles. The number of anionic environments found in the m-Ut(750)(n)Eu(CF3SO3)(3) family confirms the rich coordinating possibilities offered by polymer systems incorporating trivalent triflate salts.