Nitromethane anionic ligands

For 2,7-dmnapy complexes of the same rare earth, the recorded intensities of the nitrate complexes are always greater than those in which acac is the anion. Conductivity measurements on nitromethane solutions of M(acac)3(2,7-dmnapy) give A values of 6-9 which are typical of nonelectrolytes (II, 12). IR spectra of the acac complexes have vCO absorptions at approximately 1600 and 915 cm" and i/M-0 bands at 405 and 313 cm" These absorptions and the lack of a 1700-cm band indicate that both oxygens of each of the acac units are coordinated to the metal (II, 30). The more intense fluorescence of the nitrate complex may result from the presence of a second 2,7-dmnapy ligand which would increase the coordination number of the rare earth from 8 to 10. The triplet state of acac is reported at 25,300 cm (31). The triplet state of napy at 22,210 cm" is closer to the rare earth resonance levels and may contribute to a more efficient energy transfer which in turn would enhance fluorescence intensity. 

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