Mononuclear Zn(II) complexes with the general formula [Zn(L)2] have been synthesized in good yields by reacting Zn(OAc)2 with HL in a ratio of 1 : 2 in methanol solvent. Here L is the deprotonated form of 6-[(quinolin-8-ylamino)methylene]cyclohexa-2,4-dienone (HL1), 4-chloro-6-[(quinolin-8-ylamino)methylene]cyclohexa-2,4-dienone (HL2), 4-methyl-6-[(quinolin-8-ylamino)methylene]cyclohexa-2,4-dienone (HL3), 2,4-dimethyl-6-[(quinolin-8-ylamino) methylene]cyclohexa-2,4-dienone (HL4), 2-methoxy-6-[(quinolin-8-ylamino) methylene]cyclohexa-2,4-dienone (HL5). The electronic structures and photophysical properties of the ligands were calculated by DFT and TDDFT methods. The X-ray structure of one complex is reported. The ligands have a strong binding ability [(0.75–15.37) × 104] and ratiometric response to Zn2+ ions. With the addition of Zn2+ ions to the ligands in THF solution a sharp color change is observed visually, and as well a significant enhancement of the fluorescence intensity and the quantum yield for this series occurs. The introduction of other metal ions having biological and environmental effects results in either unaltered or quenched emission intensity. However we observed the sensing property of the ligands strongly depends on the substituent at the ortho position of the phenol group. DFT calculation reveals that the ICT process take place from the salicylaldehyde (donor moiety) to quinoline (acceptor moiety) which is responsible for the enhancement of the fluorescence intensity of ligands after complexation.
单核Zn(II)配合物,通用公式为[Zn(L)₂],通过在
甲醇溶剂中以1:2的比例将Zn(OAc)₂与HL反应,合成得率良好。这里的L是去质子化形式的6-[(
喹啉-8-
氨基)亚甲基]
环己烯-2,4-二酮(HL1)、4-
氯-6-[(
喹啉-8-
氨基)亚甲基]
环己烯-2,4-二酮(H
L2)、4-甲基-6-[(
喹啉-8-
氨基)亚甲基]
环己烯-2,4-二酮(HL3)、2,4-二甲基-6-[(
喹啉-8-
氨基)亚甲基]
环己烯-2,4-二酮(HL4)、2-甲氧基-6-[(
喹啉-8-
氨基)亚甲基]
环己烯-2,4-二酮(HL5)。通过DFT和TDDFT方法计算了
配体的电子结构和光物理性质,并报道了一种配合物的X射线结构。
配体具有强的结合能力[(0.75–15.37) × 10⁴],以及对Zn²⁺离子的比率响应。当Zn²⁺离子加入到THF溶液中的
配体时,观察到明显的颜色变化,同时该系列的荧光强度和量子产率显著增强。引入具有
生物和环境作用的其他
金属离子结果是发射强度不变或被淬灭。然而,我们观察到
配体的传感性质强烈依赖
苯酚基团的邻位取代基。DFT计算表明ICT过程发生在
水杨 aldehyde(供体部分)和
喹啉(受体部分)之间,这对配合后的
配体荧光强度的增强起关键作用。