Two polyaminophenolic fluorescent chemosensors for H<sup>+</sup>and Zn(<scp>ii</scp>). Spectroscopic behaviour of free ligands and of their dinuclear Zn(<scp>ii</scp>) complexes
作者:Gianluca Ambrosi、Cristina Battelli、Mauro Formica、Vieri Fusi、Luca Giorgi、Eleonora Macedi、Mauro Micheloni、Roberto Pontellini、Luca Prodi
DOI:10.1039/b810228g
日期:——
The UV-Vis and fluorescence optical properties of the two polyamino-phenolic ligands 3,3′-bis[N,N-bis(2-aminoethyl)aminomethyl]-2,2′-dihydroxybiphenyl (L1) and 2,6-bis[bis(2-aminoethyl)amino]methyl}phenol (L2) were investigated in aqueous solution at different pH values as well as in the presence of Zn(II) metal ion. Both ligands show two diethylenetriamine units separated by the 1,1′-bis(2-phenol) (BPH) or the phenol (PH) for L1 and L2, respectively. Both ligands are fluorescence-emitting systems in all fields of pH examined, with L1 showing a higher fluorescence emission than L2. In particular, the emission of fluorescence mainly depends on the protonation state of the phenolic functions and thus on pH. The highest emitting species is H3L3+ for both systems, where the BPH is monodeprotonated (in L1) and the PH is in the phenolate form (in L2). On the contrary, when BPH and PH are in their neutral form both ligands show the lowest fluorescence, since H-bonds occurring between the phenol and the closest tertiary amine functions decrease fluorescence. The Zn(II)-dinuclear species are also fluorescent in the pH range where they exist; the highest emitting species being [Zn2(H−2L1)]2+ and [Zn2(H−1L2)]3+ which are present in a wide range of pH including the physiological one. Fluorescence experiments carried out at physiological pH highlighted that, in the case of L1, the presence of Zn(II) ion in solution produces a simultaneous change in λem with a drop in fluorescence due to the formation of the [Zn2(H−2L1)]2+ species, while, in the case of L2, it gives rise to a strong CHEF effect (a twenty-fold enhancement was observed) due to the formation of the [Zn2(H−1L2)]3+ species. These results, supported by potentiometric, 1H and 13C NMR experiments, are of value for the design of new efficient fluorescent chemosensors for both H+ and Zn(II) ions.
研究了 3,3′-双[N,N-双(2-氨基乙基)氨基甲基]-2,2′-二羟基联苯(L1)和 2,6-双[双(2-氨基乙基)氨基]甲基}苯酚(L2)这两种多氨基酚配体在不同 pH 值的水溶液中以及在金属锌(II)离子存在下的紫外可见光和荧光光学性质。 对于 L1 和 L2,这两种配体都显示出两个二乙烯三胺单元,分别被 1,1′-双(2-苯酚)(BPH)或苯酚(PH)隔开。 这两种配体在所考察的所有 pH 值范围内都是荧光发射系统,其中 L1 的荧光发射率高于 L2。 特别是,荧光发射主要取决于酚功能的质子化状态,因此也取决于 pH 值。 在这两种体系中,发射率最高的物种是 H3L3+,其中 BPH 为单质子化(L1 时),PH 为苯酚形式(L2 时)。 相反,当 BPH 和 PH 处于中性形态时,由于苯酚和最接近的叔胺功能之间发生的 H 键会降低荧光,因此这两种配体都显示出最低的荧光。 Zn(II)- 二核物种在它们存在的 pH 值范围内也会发出荧光;发射率最高的物种是[Zn2(H-2L1)]2+ 和[Zn2(H-1L2)]3+,它们存在于包括生理 pH 值在内的广泛 pH 值范围内。 在生理 pH 值下进行的荧光实验表明,在 L1 的情况下,由于形成了 [Zn2(H-2L1)]2+ 物种,溶液中 Zn(II)离子的存在会同时引起 λem 的变化和荧光的下降;而在 L2 的情况下,由于形成了 [Zn2(H-1L2)]3+ 物种,会引起强烈的 CHEF 效应(观察到增强了 20 倍)。 这些结果得到了电位计、1H 和 13C NMR 实验的支持,对于设计 H+和 Zn(II)离子的新型高效荧光化学传感器具有重要价值。