Ambili Raj D B, Biju Silvanose, Reddy M L P
Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science & Technology (NIIST), CSIR, Thiruvananthapuram, 695 019, India.
Dalton Trans. 2009 Sep 28(36):7519-28. doi: 10.1039/b907031a. Epub 2009 Jul 23.
A novel beta-diketone ligand, 4,4,5,5,5-pentafluoro-1-(9H-fluoren-2-yl)-1,3-pentanedione (Hpffpd), which contains a polyfluorinated alkyl group, as well as a long conjugated fluorene unit, and a chelate phosphine oxide ligand, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide (DDXPO) were synthesized and utilized for the synthesis of two new europium complexes [Eu(pffpd)3(C2H5OH)(H2O)] 1 and [Eu(pffpd)3(DDXPO)] 2. For comparison, the [Eu(pffpd)3(DPEPO)] 3 complex was also synthesized involving a known chelate phosphine oxide, bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO). The synthesized complexes have been characterized by various spectroscopic techniques and their solid-state photophysical properties were investigated. The single-crystal X-ray diffraction analyses of 2 and 3 revealed that these complexes are mononuclear, and that the central Eu3+ ion is surrounded by eight oxygen atoms, six of which are from the three bidentate fluorinated beta-diketonates, and the other two oxygen atoms from the chelate phosphine oxide. The coordination polyhedra can be described as distorted square antiprism. Compound 2 has a solid-state photoluminescence quantum yield of 48%, which is about two times higher than that of compound 3 (28%). This may be due to the fact that DDXPO in 1 has the mezzo first triplet excited state energy level (T1) between the first singlet excited energy level (S1) and T1 of Hpffpd, which may support one more additional energy transfer from the T1 energy level of DDXPO to that of Hpffpd, and consequently improves the energy transfer in the Eu3+ complex. Furthermore, DDXPO (average Eu-O = 2.34 A) in complex 2 coordinates more strongly with the central Eu3+ as compared to DPEPO in complex 3 (average Eu-O = 2.38 A) which can improve the energy transfer between the ligands and central metal ion, and consequently enhances the photoluminescence efficiency of the corresponding Eu3+ complex.
合成了一种新型的β-二酮配体4,4,5,5,5-五氟-1-(9H-芴-2-基)-1,3-戊二酮（Hpffpd），其含有多氟烷基以及长共轭芴单元，还合成了一种螯合氧化膦配体4,5-双（二苯基膦基）-9,9-二甲基氧杂蒽（DDXPO），并将其用于合成两种新型铕配合物[Eu(pffpd)3(C2H5OH)(H2O)] 1和[Eu(pffpd)3(DDXPO)] 2。为作比较，还合成了涉及已知螯合氧化膦双（2-（二苯基膦基）苯基）醚氧化物（DPEPO）的[Eu(pffpd)3(DPEPO)] 3配合物。通过各种光谱技术对合成的配合物进行了表征，并研究了它们的固态光物理性质。对2和3的单晶X射线衍射分析表明，这些配合物是单核的，中心Eu3+离子被八个氧原子包围，其中六个来自三个双齿氟化β-二酮酸酯，另外两个氧原子来自螯合氧化膦。配位多面体可描述为扭曲的方形反棱柱。化合物2的固态光致发光量子产率为48%，约为化合物3（28%）的两倍。这可能是由于1中的DDXPO在Hpffpd的第一单重激发能级（S1）和T1之间具有中间第一三重激发态能级（T1），这可能支持从DDXPO的T1能级到Hpffpd的T1能级的另外一次能量转移，从而改善了Eu3+配合物中的能量转移。此外，配合物2中的DDXPO（平均Eu-O = 2.34 Å）与中心Eu3+的配位比配合物3中的DPEPO（平均Eu-O = 2.38 Å）更强，这可以改善配体与中心金属离子之间的能量转移，从而提高相应Eu3+配合物的光致发光效率。
