Proton-assisted interaction between luminescent species containing diazacrown ethers and anthryl chromophores
作者:Frédérique Loiseau、Cinzia Di Pietro、Sebastiano Campagna、Marco Cavazzini、Giovanni Marzanni、Silvio Quici
DOI:10.1039/b500918a
日期:——
The multicomponent species 1 and 2 (structural formulas shown in Fig. 1), made of diazacrown receptors and anthracene-based chromophores, have been synthesized, together with 3, an already-known species containing the anthracene chromophore and an appended amino group. The absorption spectra and luminescence properties of 1–3 have been studied in acetonitrile solution, both in the absence and presence of protons. All of the compounds exhibit luminescence, the intensity of which is enhanced in the presence of protons, and have the role of inhibiting the reductive electron transfer emission quenching processes operating in non-protonated 1–3. The emission intensity of an equimolar solution of 1 and 3 is increased by proton addition, as expected, however the maximum of the intensity is reached when acid concentration is about 1.5 times higher than those of 1 or 3. This suggests that proton-assisted interaction between 1 and 3 takes place. The equimolar solution of 2 and 3 exhibits two emission features, each one assigned to a component chromophore. Low acid concentration leads to enhancement of the 400 nm emission, related to the species 3, and higher acid concentration allows for enhancement of the 520 nm emission, related to the species 2. A closer observation of the luminescence titration curve, as well as NMR data, indicates that a 2·3 adduct is present even before proton addition, and the adduct is further stabilized by protonation to form 2·H·3.
由二氮杂冠受体和基于蒽的发色团组成的多组分物种1和2(结构式如图1所示)以及含有蒽发色团和附加氨基的已知物种3已经合成。 1-3 的吸收光谱和发光性质已经在乙腈溶液中进行了研究,无论是在质子不存在还是存在的情况下。所有化合物均表现出发光,其强度在质子存在下增强,并具有抑制非质子化 1-3 中还原电子转移发射猝灭过程的作用。正如预期的那样,1 和 3 的等摩尔溶液的发射强度通过添加质子而增加,但是当酸浓度比 1 或 3 的溶液高约 1.5 倍时,强度达到最大值。这表明质子辅助相互作用1 和 3 之间发生。 2 和 3 的等摩尔溶液表现出两种发射特征,每一种都分配给一种组分发色团。低酸浓度导致与物种 3 相关的 400 nm 发射增强,而较高的酸浓度则导致与物种 2 相关的 520 nm 发射增强。 更仔细地观察发光滴定曲线以及 NMR数据表明,甚至在质子添加之前就存在2·3加合物,并且该加合物通过质子化进一步稳定以形成2·H·3。