Six novel luminescent lanthanide-2-phenylpyrimidine-carboxylate frameworks, namely, [Ln(ppmc)3(phen)] (Ln = Eu (1), Tb (2)), [Ln(ppmc)2(C2O4)0.5(H2O)] (Ln = Eu (3), Tb (4)), [Eu(ppmdc)(phen)(C2O4)0.5]·0.5H2O} (5) and [Tb(ppmdc)(benzoate)(phen)] (6) (Hppmc = 2-phenylpyrimidine-4-carboxylic acid, H2ppmdc = 2-phenylpyrimidine-4,6-dicarboxylic acid) have been synthesized. The X-ray structure analyses reveal that all of the compounds contain carboxylate-bridged dimer units; however, coordination environments of Ln3+ ions, bridging modes of carboxylate, and the linkage between them are different. In the isostructural compounds 1 and 2, extensive π–π stacking exists between the anti–anti carboxylate bridged dimer. However, syn–anti carboxylate bridges are found in compounds 3 and 4 in which oxalate connects the dimers to form 1D chains. Compound 5 has a 2D structure connected by both μ4-ppmdc2− and oxalate in which the carboxylates adopt both anti–anti and chelate-bridging modes. Compound 6 featuring 1D chains also contains anti–anti carboxylate-bridged dimers that are linked by the μ3-ppmdc2− ligand. All six compounds show characteristic red or green emission attributed to Eu3+ and Tb3+. The luminescence lifetime and quantum yield are presented and discussed in detail. The use of different ligands and reaction conditions has led to distinct coordination environments of lanthanide ions and the aggregation of dimeric units, which are considered as the dominating factors for the resulting photoluminescence behaviour of solid samples.
六种新型发光
镧系元素-2-
苯基嘧啶-
羧酸盐骨架,即[Ln(ppmc)3(phen)] (Ln = Eu (1), Tb (2))、[Ln(ppmc)2(
C2O4)0.5(
H2O) )] (Ln = Eu (3), Tb (4)), [Eu(ppmdc)(phen)( )0.5]·0.5 } (5) 和 [Tb(ppmdc)(
苯甲酸盐)(phen)] (6) (Hppmc = 2-
苯基嘧啶-4-
羧酸,H2ppmdc = 2-
苯基嘧啶-4,6-二
羧酸)已合成。 X射线结构分析表明所有化合物均含有
羧酸桥二聚体单元;然而,Ln3+离子的配位环境、
羧酸盐的桥联模式以及它们之间的连接是不同的。在同构化合物 1 和 2 中,抗-抗
羧酸桥二聚体之间存在广泛的 π-π 堆积。然而,在化合物 3 和 4 中发现了顺反
羧酸酯桥,其
中草酸连接二聚体形成一维链。化合物5具有由μ4-ppmdc2−和
草酸盐连接的二维结构,其中
羧酸盐采用抗-抗和螯合-桥接模式。具有一维链的化合物 6 还包含通过 μ3-ppmdc2−
配体连接的抗抗
羧酸桥二聚体。所有六种化合物均显示出由 Eu3+ 和 Tb3+ 引起的特征性红色或绿色发射。详细介绍并讨论了发光寿命和量子产率。不同
配体和反应条件的使用导致了不同的
镧系离子配位环境和二聚体单元的聚集,这被认为是固体样品光致发光行为的主导因素。