Four new macrocyclic-phthalimide ligands were synthesised via the coupling of N-(3-bromopropyl)phthalimide either to cyclen (1,4,7,10-tetraazacyclododecane) itself or its carboxylate-functionalized analogues, and photophysical studies were carried out on their corresponding Tb(III) complexes in aqueous media as a function of pH. Luminescence intensities of Tb·L1a1a–Tb·L3a3a were in ‘switched off’ mode under acidic conditions (pH < 4), and were activated on progression to basic conditions as the phthalimido functions therein were hydrolysed to their corresponding phthalamates Tb·L1b1b1b–Tb·L3b3b3b. Emission of phthalamate-based macrocyclic Tb(III) complexes Tb·L1b1b1b–Tb·L3b3b3b was in ‘switched on’ mode between pH 4 and 11, exhibiting high quantum yields (Φ) and long lifetimes (τ) of the order of milliseconds at pH ∼ 6. Tb(III) emissions were found to decline with increasing number of chromophores. The values of Φ and τ were 46% and 2.4 ms respectively for Tb·L1b1b at pH ∼ 6 when activated. This is the best pH-dependent sensor based on a Tb(III) complex reported to date, benefiting from the macrocyclic architecture of the ligand.
通过将 N-(3-
溴丙基)邻苯二甲
酰亚胺与环烯(1,4,7,10-四
氮杂环十二烷)本身或其羧基功能化类似物偶联,合成了四种新的大环邻苯二甲
酰亚胺配体。在酸性条件下(pH < 4),Tb-L1a1a-Tb-L3a3a 的发光强度处于 "关闭 "模式,而在碱性条件下,当其中的邻苯二甲酰亚氨基官能团水解为相应的邻苯二甲酸盐 Tb-L1b1b1b-Tb-L3b3b 时,发光强度被激活。邻苯二甲酸酯基大环 Tb(III) 复合物 Tb-L1b1b1b-Tb-L3b3b3b 的发射在 pH 值为 4 到 11 之间处于 "开启 "模式,在 pH 值为 ∼ 6 时表现出高量子产率(Φ)和长寿命(τ),约为几毫秒。研究发现,随着发色团数量的增加,锑(III)的排放量也在下降。在 pH 值为 6 时,Tb-L1b1b 激活后的Φ和τ值分别为 46%和 2.4 毫秒。得益于配体的大环结构,这是迄今为止报道的基于
锑(III)复合物的最佳 pH 依赖性传感器。