Structures, luminescence and vibrational spectroscopy of europium and terbium nitro- and dinitro-substituted benzoates. Nitro groups as quenchers of Ln³⁺ luminescence

详细信息	查看全文 | 推荐本文 |

• 作者：V. Tsaryuk^a ; ^{vtsaryuk@mail.ru} ; ^{vit225@ire216.msk.su} ; V. Kudryashova^a ; P. Gawryszewska^b ; R. Szostak^b ; A. Vologzhanina^c ; K. Zhuravlev^a ; Z. Klemenkova^c ; J. Legendziewicz^b ; V. Zolin^a
• 关键词：Eu3+ ; Tb3+ ; Nitrobenzoate ; 1 ; 10-Phenanthroline ; 2 ; 2&prime ; -Bipyridine ; Luminescence ; Raman spectra ; IR spectra ; Energy transfer ; X-ray crystal structure
• 刊名：Journal of Photochemistry and Photobiology A ; Chemistry
• 出版年：2012
• 期刊代码：66_10106030
• 类别：ch
• 出版时间：1 July, 2012
• 卷：239
• 期：Complete
• 页码：37-46
• 文件大小：900 K

摘要

The nitro-substituted benzoates Ln(NBenz)₃路nH₂O, Ln(DNBenz)₃路nH₂O, Ln(NBenz)₃路L路nH₂O and Ln(DNBenz)₃路L路nH₂O (Ln = Eu, Tb; NBenz = 2- and 4-nitrobenzoate anions, DNBenz = 3,5- and 2,5-dinitrobenzoate anions; L = Phen and Bpy) were investigated by methods of luminescence and vibrational Raman and IR spectroscopy. The crystal structures of [Eu(4-NBenz)₃路(H₂O)₂]路0.5H₂O and [Eu₂(4-NBenz)₆路Bpy₂路(H₂O)₂]路2H₂O (1) were solved by X-ray diffraction methods. Known structural data for lanthanide nitrobenzoates are analyzed. The influence of NO₂ groups located in different positions of benzene ring on the structure of Ln³⁺ coordination centre and on processes of the excitation energy transfer to Ln³⁺ ion was studied. The presence of electron-withdrawing nitro groups at aromatic ring of the ligand dramatically decreases Eu³⁺ and Tb³⁺ luminescence efficiencies. This fall amounts to factor 鈭?0² in comparison with europium and terbium benzoates. Low sensitization efficiency of Ln³⁺ luminescence in nitrobenzoates is caused by a dissipation of the excitation energy through the ligand excited state corresponding to transition between the NO₂ oxygen lone pairs orbital and the 蟺* orbital of nitrobenzoate ligand. A low energy of the ligand state in comparison with Tb^{3+ 5}D₄ state makes for a supplementary reduction of the sensitization of Tb³⁺ luminescence. In ternary compounds, an interligand energy transfer from the Phen or Bpy molecule to nitrobenzoate anion with following quenching due to the nitrobenzoate non-radiative relaxation is observed.