Bifunctional ZnIILnIII Dinuclear Complexes Combining Field Induced SMM Behavior and Luminescence: Enhanced NIR Lanthanide Emission by 9-Anthracene Carboxylate Bridging Ligands

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• 作者：María A. Palacios ; Silvia Titos-Padilla ; José Ruiz ; Juan Manuel Herrera ; Simon J. A. Pope ; Euan K. Brechin ; Enrique Colacio
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：February 3, 2014
• 年：2014
• 卷：53
• 期：3
• 页码：1465-1474
• 全文大小：416K
• ISSN：1520-510X

文摘

There were new dinuclear Zn^II鈥揕n^III complexes of general formulas [Zn(渭-L)(渭-OAc)Ln(NO₃)₂] (Ln^III = Tb (1), Dy (2), Er (3), and Yb (4)), [Zn(渭-L)(渭-NO₃)Er(NO₃)₂] (5), [Zn(H₂O)(渭-L)Nd(NO₃)₃]路2CH₃OH (6), [Zn(渭-L)(渭-9-An)Ln(NO₃)₂]路2CH₃CN (Ln^III = Tb (7), Dy (8), Er (9), Yb(10)), [Zn(渭-L)(渭-9-An)Yb(9-An)(NO₃)₃]路3CH₃CN (11), [Zn(渭-L)(渭-9-An)Nd(9-An)(NO₃)₃]路2CH₃CN路3H₂O (12), and [Zn(渭-L)(渭-9-An)Nd(CH₃OH)₂(NO₃)]ClO₄路2CH₃OH (13) prepared from the reaction of the compartmental ligand N,N鈥?i>,N鈥?trimethyl-N,N鈥?bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H₂L), with ZnX₂路nH₂O (X = NO₃^{鈥?/sup> or OAc鈥?/sup>) salts, Ln(NO₃)₃路nH₂O, and, in some instances, 9-anthracenecarboxylate anion (9-An). In all these complexes, the ZnII ions invariably occupy the internal N₃O₂ site whereas the LnIII ions show preference for the O₄ external site, giving rise to a Zn(渭-diphenoxo)Ln bridging fragment. Depending on the ZnII salt and solvent used in the reaction, a third bridge can connect the ZnII and LnIII metal ions, giving rise to triple-bridged diphenoxoacetate in complexes 1鈥?b>4, diphenoxonitrate in complex 5, and diphenoxo(9-anthracenecarboxylate) in complexes 8鈥?b>13. DyIII and ErIII complexes 2, 8 and 3, 5, respectively, exhibit field induced single molecule magnet (SMM) behavior, with U_eff values ranging from 11.7 (3) to 41(2) K. Additionally, the solid-state photophysical properties of these complexes are presented showing that ligand L2- is able to sensitize TbIII- and DyIII-based luminescence in the visible region through an energy transfer process (antenna effect). The efficiency of this process is much lower when NIR emitters such as ErIII, NdIII, and YbIII are considered. When the luminophore 9-anthracene carboxylate is incorporated into these complexes, the NIR luminescence is enhanced which proves the efficiency of this bridging ligand to act as antenna group. Complexes 2, 3, 5, and 8 can be considered as dual materials as they combine SMM behavior and luminescent properties.}