The ligand H2L = 2,2â²-bipyridine-6,6â²-dicarboxylic acid reacts with Ln(NO3)3·xH2O (x = 6, Ln = Eu, Tb; x = 5, Ln = Gd) in MeOH/Et3N to give complexes with 1â¶2 and 2â¶3 metalâ¶ligand stoichiometry, (Et3NH)[LnL2] and [Ln2L3(H2O)3]·xH2O (x = 1, Ln = Eu, Tb; x = 0, Ln = Gd) which have been isolated and characterised. A sizeable quantum yield is obtained for the 1â¶2 Euâ¶Ligand complex in aqueous solution (QEuabs = 11.5 ± 2.3% at pH = 6.6), pointing to an efficient ligand-to-metal energy transfer. The presence of some inner-sphere interaction with water was deduced from Eu(5D0) lifetime measurements in water (0.86 ± 0.01 ms vs. 1.55 ± 0.02 ms in the solid state between 10 and 295 K, qest = 0.3â0.4 water molecule). For [TbL2]â, sensitisation of TbIII also occurs (QTbabs = 6.3 ± 1.3% at pH = 6.6) but the Tb(5D4) excited level is de-populated at room temperature by a back-transfer process to the ligand. The crystal structure obtained for the 2â¶3 Tbâ¶ligand complex evidences two distinct terbium sites, one TbIII being complexed to two ligands affording a mono-anionic complex, itself linked to the second terbium ion with a μ-carboxylate bridge; the generic formulation of the crystallised complex is [TbL2-μ-TbL(H2O)3]·2H2O· 2MeOH. Consecutive dimers are linked by an elaborate network of H-bonds involving interstitial solvent molecules. A photophysical study of the 2â¶3 Euâ¶Ligand complex in the solid state points to the same structural features, revealing two metal ion sites with essentially no bonded water (q = 0.3, site I) and with 3 co-ordinated water molecules (q = 2.8, site II), respectively. The H2L synthon is therefore an interesting building block for the design of elaborate compartmental ligands and/or of supramolecular functional assemblies.
配体 H2L=2,2-联
吡啶-6,6-二
甲酸与 Ln(
NO3)3·x 反应 (x=6, Ln=Eu, Tb; x=5, Ln= Gd) 在 MeOH/Et3N 中,得到与 1-2 和 2-3
金属
配体化学计量的配合物,(Et3NH)[Ln
L2] 和 [Ln2L3(
H2O)3]·x (x=1, Ln) = Eu, Tb; x = 0, Ln = Gd) 已被分离和表征。
水溶液中的 1-2 Eu-
配体络合物获得了相当大的量子产率(QEuabs = 11.5 ± 2.3%,pH = 6.6),表明
配体到
金属的能量转移有效。从
水中的 Eu(5D0) 寿命测量中推断出与
水存在一些内球相互作用(在 10 到 295 K 之间,固态下为 0.86±0.01 ms 与 1.55±0.02 ms,qest = 0.3-0.4个
水分子)。对于 [Tb
L2]-,TbIII 也会发生敏化(QTbabs = 6.3± 1.3%,pH = 6.6),但 Tb(5
D4) 激发
水平在室温下通过反向转移过程减少至
配体。 2-3 Tb-
配体络合物获得的晶体结构证明了两个不同的
铽位点,一个 TbIII 与两个
配体络合,形成单阴离子络合物,其本身通过 μ-
羧酸根桥与第二个
铽离子相连;结晶复合物的通用配方是[Tb
L2-μ-TbL( )3]·2 ·2MeOH。连续二聚体通过涉及间隙溶剂分子的复杂氢键网络连接。对固态 2-3 Eu-
配体配合物的光物理研究指出了相同的结构特征,揭示了两个基本上没有键合
水的
金属离子位点(q = 0.3,位点 I)和 3 个配位的
水分子(q = 2.8,位点 II)。因此,H2L 合成子是设计精心设计的区室
配体和/或超分子功能组件的一个有趣的构建模块。