Lanthanide ions emitting in the near-infrared (NIR) region possess an intrinsically small molar absorption coefficient in the ultraviolet (UV)-vis-NIR spectrum, which is unfavourable for pumping efficiency. On the contrary, using organic lanthanide complexes it is possible to populate the excited state levels of the emitting ion through an efficient intramolecular energy transfer from the optically excited ligands, which act as light-harvesting antennae. With the aim of studying and maximizing the transfer to lanthanide metals, we have synthesized oligothiophene and thiophenefluorene ligands bearing carboxylate clamps able to complex erbium and other lanthanide 3(+) ions. The complexes of {4'-(hydroxycarbonyl)methyi-[2,2';5',2 '']terthiophen-3'-yl} acetic acid and 9-(hydroxycarbonyl)-methyl-2,7-dithien-2-yl-[fluoren-9-yl-]acetic acid with Er3+ and different ancillary ligands have been prepared and their optical properties were carefully studied. Moreover, relaxation dynamics measurements have been carried out on all complexes in order to determine emission lifetimes, which result to be of the order of magnitude 2 mu s. Quantum chemical calculations have been performed to explain optical absorption data in terms of different coordination types. The complexes containing phenanthroline/pyridine are modelled by adding to the dianion of the ligand one univalent/divalent counterion. The absorption spectra computed in this way are in close agreement with experiment, and the univalent -> divalent theoretical wavelength shift goes in the right direction. The addition of a counterion has an even bigger effect on the triplet states, and hence on their matching with the emitting states of the ion.
Destri, S., Pasini, M., Porzio, W., Rizzo, F., Dellepiane, G., Ottonelli, M., et al. (2007). New erbium complexes emitting in infrared region based on oligothiophene and thiophenefluorene carboxylate. JOURNAL OF LUMINESCENCE, 127(2), 601-610 [10.1016/j.jlumin.2007.03.018].
New erbium complexes emitting in infrared region based on oligothiophene and thiophenefluorene carboxylate
MEINARDI, FRANCESCO;
2007
Abstract
Lanthanide ions emitting in the near-infrared (NIR) region possess an intrinsically small molar absorption coefficient in the ultraviolet (UV)-vis-NIR spectrum, which is unfavourable for pumping efficiency. On the contrary, using organic lanthanide complexes it is possible to populate the excited state levels of the emitting ion through an efficient intramolecular energy transfer from the optically excited ligands, which act as light-harvesting antennae. With the aim of studying and maximizing the transfer to lanthanide metals, we have synthesized oligothiophene and thiophenefluorene ligands bearing carboxylate clamps able to complex erbium and other lanthanide 3(+) ions. The complexes of {4'-(hydroxycarbonyl)methyi-[2,2';5',2 '']terthiophen-3'-yl} acetic acid and 9-(hydroxycarbonyl)-methyl-2,7-dithien-2-yl-[fluoren-9-yl-]acetic acid with Er3+ and different ancillary ligands have been prepared and their optical properties were carefully studied. Moreover, relaxation dynamics measurements have been carried out on all complexes in order to determine emission lifetimes, which result to be of the order of magnitude 2 mu s. Quantum chemical calculations have been performed to explain optical absorption data in terms of different coordination types. The complexes containing phenanthroline/pyridine are modelled by adding to the dianion of the ligand one univalent/divalent counterion. The absorption spectra computed in this way are in close agreement with experiment, and the univalent -> divalent theoretical wavelength shift goes in the right direction. The addition of a counterion has an even bigger effect on the triplet states, and hence on their matching with the emitting states of the ion.
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