Intrazeolite photochemistry.: 20.: Characterization of highly luminescent europium complexes inside zeolites
Intrazeolite photochemistry.: 20.: Characterization of highly luminescent europium complexes inside zeolites
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DOI：
10.1021/jp980669g
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发表时间：
1998-10-29
影响因子：
3.3
通讯作者：
Scaiano, JC
中科院分区：
文献类型：
--
作者：
Alvaro, M;Fornés, V;Scaiano, JC
通过在Y、丝光沸石和ZSM-5分子筛中吸附Eu（3+）与2，2 ′-联吡啶（bipy）、苯甲酰基三氟丙酮（btfa）、1，10-邻菲咯啉（phen）和吡啶二甲酸（dpic）的配合物，合成了Eu（3+）与Y、丝光沸石和ZSM-5分子筛的配合物。通过改变Eu（3+）的含量和Eu（3+）：配体的比例得到不同的样品。络合物的形成及其化学计量已被评估元素化学分析（燃烧和原子吸收）和热重-差示扫描量热法以及红外和漫反射（DR）光谱。固体的DR光谱的显著特征是在500 nm区域中存在中等强度的带，这对于溶液中的相同络合物是不存在的。所有的样品，包括那些不含任何有机配体，表现出室温发射激光激发时，虽然发光强度显着增加络合。的发射寿命是在毫秒的时间尺度，并不遵循简单的一级动力学。关于发光衰减，我们观察到：（i）配合物发光在分子筛中比在溶液中寿命长得多;（ii）发光寿命的顺序为dpic > phen > bipy > bfta;（iii）寿命随配体的加入量而增加;（iv）随分子筛中Eu（3+）含量的增加衰减更快;（v）发射寿命按ZSM-5 >丝光沸石> Y的顺序延长。这些事实已被合理化的结果，在复杂的阻碍替代非发射性失活途径在沸石介质中经历的构象刚度的增加。固体的脱水和随后的D（2）O再水化不改变未络合的Eu（3+）-Y样品的衰变，但增加Y沸石内Eu-btfa络合物的寿命2倍。这表明发射Eu（3+）没有被溶剂化（可能位于方钠石笼和六棱柱内），而Eu-btfa络合物与单个H（2）O分子配位。
Four organometallic complexes of Eu(3+) With 2,2'-bipyridine (bipy), benzoyltrifluoroacetone (btfa), 1,10-phenanthroline (phen), and dipicolinic acid (dpic) have been prepared in Y, mordenite, and ZSM-5 zeolites by adsorbing the ligand into Eu(3+)-doped zeolites. Different samples were obtained varying the Eu(3+) content and the Eu(3+):ligand ratio. Formation of the complexes and their stoichiometry have been assessed by elemental chemical analysis (combustion and atomic absorption) and thermogravimetry-differential scanning calorimetry as well as IR and diffuse reflectance (DR) spectroscopies. The distinctive feature of DR spectra of the solids is the presence of a band of medium intensity in the 500 nm region that is absent for the same complexes in solution. All the samples, including those that do not contain any organic ligand, exhibit room-temperature emission upon laser excitation, although luminescence intensity notably increases upon complexation. The emission lifetimes are in the millisecond time scale and do not follow simple first-order kinetics. Concerning the emission decay, the following observations were made: (i) the complex luminescence is much longer lived inside the zeolites than in solution; (ii) the emission lifetime follows the order dpic > phen > bipy > bfta; (iii) lifetime increases with the amount of the ligand incorporated; (iv) the decays are more rapid as the Eu(3+) content of the zeolite increases; and (v) emission becomes longer lived in the order ZSM-5 > mordenite > Y. These facts have been rationalized as the result of an increase in the conformational rigidity experienced by the complex that impedes alternative nonemissive deactivation pathways in zeolite media. Dehydration of the solids and subsequent D(2)O rehydration does not alter the decay of the uncomplexed Eu(3+)-Y samples but increases the lifetime of the Eu-btfa complex inside Y zeolite by a factor of 2. This is indicative that emitting Eu(3+) are not solvated (probably located inside the sodalite cages and hexagonal prisms), while the Eu-btfa complex is coordinated with a single H(2)O molecule.