Chemical Sciences and Technology Division, CSIR-Network Institutions on Solar Energy, National Institute for Interdisciplinary Science and Technology (NIIST), Thiruvananthapuram-695 019, India.
Dalton Trans. 2012 Dec 28;41(48):14671-82. doi: 10.1039/c2dt31827j.
A new aromatic carboxylate ligand, 4-[4-(9H-carbazol-9-yl)butoxy]benzoic acid (HL), has been synthesized by the replacement of the hydroxyl hydrogen of 4-hydroxy benzoic acid with a 9-butyl-9H-carbazole moiety. The anion derived from HL has been used for the support of a series of lanthanide coordination compounds [Ln = Eu (1), Gd (2) and Tb (3)]. The new lanthanide complexes have been characterized by a variety of spectroscopic techniques. Complex 3 was structurally authenticated by single-crystal X-ray diffraction and found to exist as a solvent-free 1D coordination polymer with the formula Tb(L)(3). The structural data reveal that the terbium atoms in compound 3 reside in an octahedral ligand environment that is somewhat unusual for a lanthanide. It is interesting to note that each carboxylate group exhibits only a bridging-bidentate mode, with a complete lack of more complex connectivities that are commonly observed for extended lanthanide-containing solid-state structures. Examination of the packing diagram for revealed the existence of two-dimensional molecular arrays held together by means of CH-π interactions. Aromatic carboxylates of the lanthanides are known to exhibit highly efficient luminescence, thus offering the promise of applicability as optical devices. However, due to difficulties that arise on account of their polymeric nature, their practical application is somewhat limited. Accordingly, synthetic routes to discrete molecular species are highly desirable. For this purpose, a series of ternary lanthanide complexes was designed, synthesized and characterized, namely [Eu(L)(3)(phen)] (4), [Eu(L)(3)(tmphen)] (5), [Tb(L)(3)(phen)] (6) and [Tb(L)(3)(tmphen)] (7) (phen = 1,10-phenanthroline and tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline). The photophysical properties of the foregoing complexes in the solid state at room temperature have been investigated. The quantum yields of the ternary complexes 4 (9.65%), 5 (21.00%), 6 (14.07%) and 7 (32.42%), were found to be significantly enhanced in the presence of bidentate nitrogen donors when compared with those of the corresponding binary compounds 1 (0.11%) and 3 (1.45%). Presumably this is due to effective energy transfer from the ancillary ligands.
一种新的芳香羧酸配体，4-[4-(9H-咔唑-9-基)丁氧基]苯甲酸（HL），是通过用 9-丁基-9H-咔唑取代 4-羟基苯甲酸的羟基氢合成的。HL 的阴离子被用于支持一系列镧系元素配位化合物[Ln=Eu（1），Gd（2）和Tb（3）]。新型镧系元素配合物通过各种光谱技术进行了表征。配合物 3 通过单晶 X 射线衍射结构鉴定，并发现其为无溶剂的 1D 配位聚合物，其化学式为[Tb（L）（3）]（n）。结构数据表明，化合物 3 中的铽原子位于八面体配体环境中，这对于镧系元素来说有些不寻常。有趣的是，每个羧酸根仅表现出桥联双齿模式，完全没有通常在扩展的含镧系元素固态结构中观察到的更复杂的连接性。对堆积图的检查表明，存在由 CH-π相互作用结合在一起的二维分子阵列。众所周知，镧系元素的芳香羧酸具有高效的发光性能，因此有望作为光学器件应用。然而，由于其聚合物性质带来的困难，其实际应用有些受限。因此，高度期望有离散分子物种的合成途径。为此，设计、合成和表征了一系列三元镧系元素配合物，即[Eu（L）（3）（phen）]（4），[Eu（L）（3）（tmphen）]（5），[Tb（L）（3）（phen）]（6）和[Tb（L）（3）（tmphen）]（7）（phen=1,10-邻菲罗啉和 tmphen=3,4,7,8-四甲基-1,10-邻菲罗啉）。在室温下，研究了上述配合物在固态中的光物理性质。与相应的二元化合物 1（0.11%）和 3（1.45%）相比，三元配合物 4（9.65%）、5（21.00%）、6（14.07%）和 7（32.42%）的量子产率在存在双齿氮供体时显著提高。这可能是由于辅助配体的有效能量转移所致。
