Structural and photoluminescent studies of lanthanide complexes with tripodal triRNTB (N-substituted tris(benzimidazol-2-ylmethyl)amine): ligand substituent, anionic and secondary ligand effects
作者:Mei Pan、Xiang-Li Zheng、Yu Liu、Wei-Sheng Liu、Cheng-Yong Su
DOI:10.1039/b818322h
日期:——
Six N-substituted NTB ligands (NTB = (tris(benzimidazol-2-ylmethyl)amine), namely, triMeNTB (L1), triEtNTB (L2), triPrNTB (L3), triBuNTB (L4), triAlNTB (L5) and triBzNTB (L6), have been synthesized through replacing the H atoms on the NH groups by methyl, ethyl, npropyl, nbutyl, allyl, and benzyl groups, respectively. Their corresponding Sm3+, Eu3+ and Tb3+ complexes consisting of different anions or secondary ligands have been prepared and characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction measurements. Three types of structural models have been obtained: ML2 where two triTNTB ligands wrap around the Ln3+ ion with anions (ClO4− and CF3SO3−) free of coordination, MLA3 where one triRNTB ligand holds the Ln3+ ion with anions (Cl−, NO3− and picrate) participating in coordination, and MLL′3 where one triNTB ligand and three secondary antipyrine ligands coordinate with the Ln3+ ion. The Ln3+ ions in ML2 type complexes are 8-coordinating and display a slightly distorted cubic (LnN8) coordination geometry. The Ln3+ ions in MLA3 and MLL′3 types complexes show two different coordination geometries: one is 7-coordinating (MLA3 with Cl− anion and MLL′3), which can be described as a severely distorted cube short of one corner (LnN4Cl3 or LnN4O3), and the other is 10-coordinating (MLA3 with NO3− and picrate anions) which can be regarded as a severely distorted cube with one corner substituted by a three-atom cap (LnN4O6). The photoluminescent study reveals that the complexes with different Ln3+ ions show a general luminescent intensity tendency of Tb > Eu > Sm. The modification of the NTB molecule by altering R groups tunes the triplet states of the ligands and results in differentiable photophysical properties of the complexes. The anions or secondary ligand also have remarkable effects on the luminescent properties of the complexes.
通过将 NH 基团上的 H 原子分别替换为甲基、乙基、正丙基、正丁基、烯丙基和苄基,合成了六种 N 取代的 NTB 配体(NTB = (三(苯并咪唑-2-基甲基)胺),即 triMeNTB (L1)、triEtNTB (L2)、triPrNTB (L3)、triBuNTB (L4)、triAlNTB (L5) 和 triBzNTB (L6)、是分别用甲基、乙基、正丙基、正丁基、烯丙基和苄基取代 NH 基上的 H 原子合成的。通过元素分析、红外光谱和单晶 X 射线衍射测量,制备了由不同阴离子或次级配体组成的相应 Sm3+、Eu3+ 和 Tb3+ 复合物,并对其进行了表征。得到了三种结构模型:在 ML2 中,两个三硝基甲苯配体环绕 Ln3+ 离子,阴离子(ClO4- 和 CF3SO3-)不参与配位;在 MLA3 中,一个三硝基甲苯配体抱住 Ln3+ 离子,阴离子(Cl-、NO3- 和苦味酸盐)参与配位;在 MLL′3 中,一个三硝基甲苯配体和三个次级反吡啶配体与 Ln3+ 离子配位。ML2 型配合物中的 Ln3+ 离子具有 8 个配位,并显示出略微扭曲的立方(LnN8)配位几何形状。MLA3 和 MLL′3 型配合物中的 Ln3+ 离子显示出两种不同的配位几何:一种是 7 配位(带有 Cl- 阴离子和 MLL′3 的 MLA3),可被描述为缺少一个角的严重扭曲立方体(LnN4Cl3 或 LnN4O3);另一种是 10 配位(带有 NO3- 和苦味酸根阴离子的 MLA3),可被描述为一个角被三原子帽取代的严重扭曲立方体(LnN4O6)。光致发光研究表明,不同 Ln3+ 离子的配合物显示出锑 > Eu > Sm 的总体发光强度趋势。通过改变 R 基团对 NTB 分子进行修饰,可以调整配体的三重态,从而使配合物具有不同的光物理性质。阴离子或次级配体对配合物的发光特性也有显著影响。