The absorption difference, comparative absorption spectrophotometry, and quantitative analysis of 4f–4f spectra of praseodymium(III) complexes with ligands possessing varying structural features and binding capabilities have clearly indicated that the 3H4 → 3P2, 3H4 → 3P1, 3H4 → 3P0, and 3H4 → 1D2 transitions exhibit substantial intensification as well as a wide variation of oscillator strength. Since these transitions do not follow the selection rules they cannot be considered hypersensitive. Ligands such as β-diketones, Schiff bases, amino acids, diols, nucleic bases, nucleosides, nucleotides, alkoxides, and haloacetates with widely differing binding features in terms of coordinating ability, denticity, and normalized bite appear to induce, to varying degrees, high sensitivity in these non-hypersensitive transitions. The present article reports the high sensitivity of the 3H4 → 3P2, 3P1, 3P0, and 1D2, transitions of Pr(III) by considering the solution spectra of 173 species. This unique sensitivity is termed Ligand Mediated Pseudohypersensitivity. Keywords: praseodymium(III), 4f–4f transitions, hypersensitive transitions.
Hypersensitive Transitions in Rare‐Earth Ions
