Scientists directly observe rare lanthanide species that could boost green chemistry
Researchers have captured the first direct spectroscopic proof that rare-earth elements can be converted into highly reactive forms under visible light—opening the door to more efficient, sustainable chemical manufacturing. The finding could accelerate development of greener catalysts for pharmaceutical and chemical production.
Originaltitel: Divalent intermediates in lanthanide-based photocatalysts: spectroscopic characterization and reactivity
<p>The reduction of stable trivalent lanthanide species (Ln(III)) by the excited states of organic chromophores is the basis of photocatalytic divalent lanthanide-mediated reduction reactions. While indirect evidence of the photochemical formation of the reactive Ln(II) species is abundant, direct spectroscopic evidence of their presence is scarce. Here, nine chromophores with absorptions covering the near UV and visible ranges were systematically investigated in the presence of Ln(III) ions to evaluate their ability to reduce Eu(III) upon excitation with visible light to the catalytically active Eu(II) species. Irradiated mixtures of Eu(III) and the chromophores were characterized using UV-vis absorption and emission and EPR spectroscopy. Several of the chromophore-Eu(III) combinations were competent photocatalysts in the presence of N,N-diisopropylethylamine or Zn terminal reductants. These results demonstrate that a variety of visible-absorbing chromophores can efficiently generate reactive Eu(II) from Eu(III) to catalyze Ln(II)-mediated reduction reactions.</p>