EMISSION-SPECTRA OF EUROPIUM(III) COMPLEXES WITH 4-METHYLMORPHOLINE-N-OXIDE

Complexes of Eu(III) with 4-methylmorpholine-N-oxide (MMNO), with perc hlorate, hexafluorophosphate and trifluoromethane-sulfonate as counter ions were prepared and characterized by elemental analysis and IR spe ctroscopy. The room temperature fluorescence spectrum of Eu(ClO4)(3) . 6MMNO suggests an Oh symmetry for the Eu(O)(6) chromophore. The spect rum is highly modified at 77 K, suggestive of a C-3v symmetry. The ver y unusual sharp transition in the fluorescence behavior occurs at 25 K as obtained from a In intensity vs. 1/T (K), plot and is interconvert ible to the original room temperature spectrum. The spectra of the cor responding hexafluorophosphate and trifluoromethanesulfonate complexes , at both 298 and 77 K are consistent with a C-3v symmetry, no changes with temperature being observed.