Department of Chemistry, Faculty of Arts and Science, Eastern Mediterranean University, Famagusta, N. Cyprus, Mersin 10, Turkey.
Photochem Photobiol Sci. 2011 Aug;10(8):1283-93. doi: 10.1039/c1pp05019b. Epub 2011 May 6.
An oligomer (3) containing flexible hydrophilic hexa(ethylene glycol) and hydrophobic naphthalene-bisimide chromophores has been synthesized by a one-step condensation reaction and its photophysical and electrochemical properties were investigated. 3 was characterized through the data from NMR, IR, UV-vis, GPC, DSC, TGA, elemental analysis and cyclic voltammetry. The average molecular weight (M(w)) of 3 was 4430 g mol(-1). Intrinsic viscosity was measured as 0.28 dL g(-1) in m-cresol at 25 °C. It has high thermal stability (T(d) = 325 °C). Interestingly, compound 3 shows excimer-like emission in all kinds of solvents. The band gap energy (E(g)), LUMO and HOMO energy values in nonpolar and polar protic solvents were 2.71 eV/3.12 eV, -3.69 eV/-3.88 eV and -6.40 eV/-7.00 eV for 3, respectively. The oligomer showed concentration and solvent dependent fluorescent color tunability. Remarkably, the fluorescent colors of the excimer emissions at 10(-6) M concentration in CHCl(3), DMF and MeOH are light yellow, light blue-yellow and strong blue, respectively, and become more intense at higher concentrations. The excimer emission color in CHCl(3) and DMF is fluorescent yellow and changed to green in MeOH at 10(-4) M concentration. 3 shows two reversible reduction steps at -1.103 and -1.457 V (vs. ferrocene/ferrocenium) in nonpolar solvent CH(2)Cl(2) and only one at -0.917 V in (50:50) CH(3)OH-CH(3)CN binary solvent mixture with higher reversibility. Strong blue-shifts of emission band were noted in protic solvents, which confirm the existence of a negative solvatochromism probably due to protonation. The strong solvent-dependent photophysical and electrochemical properties, including the large shift of excimer emission maximum reflecting self-assembly mediated through hydrogen bonding and π-stacking interactions, make the oligomer a potential candidate for various photo-sensing applications.
一种含有柔性亲水性六（乙二醇）和疏水性萘并双咪唑发色团的低聚物（3）通过一步缩合反应合成，并对其光物理和电化学性质进行了研究。3 通过 NMR、IR、UV-vis、GPC、DSC、TGA、元素分析和循环伏安法的数据进行了表征。3 的平均分子量（M(w)）为 4430 g mol(-1)。在 25°C 的间甲酚中，特性粘度测量为 0.28 dL g(-1)。它具有很高的热稳定性（T(d) = 325°C）。有趣的是，化合物 3 在各种溶剂中均显示出激基缔合物样发射。非极性和质子性溶剂中化合物 3 的能带隙能量（E(g)）、LUMO 和 HOMO 能量值分别为 2.71 eV/3.12 eV、-3.69 eV/-3.88 eV 和-6.40 eV/-7.00 eV。低聚物表现出浓度和溶剂依赖性荧光颜色可调谐性。值得注意的是，在 10(-6) M 浓度的 CHCl(3)、DMF 和 MeOH 中，激基缔合物发射的荧光颜色分别为浅黄色、浅黄色和深蓝色，浓度越高颜色越鲜艳。在 CHCl(3)和 DMF 中，激基缔合物发射的荧光颜色为黄色，在 10(-4) M 浓度的 MeOH 中变为绿色。3 在非极性溶剂 CH(2)Cl(2)中显示出两个可逆的还原步骤，分别为-1.103 和-1.457 V（相对于铁/铁离子），而在（50:50）CH(3)OH-CH(3)CN 二元溶剂混合物中仅一个步骤为-0.917 V，具有更高的可逆性。在质子溶剂中观察到发射带的强烈蓝移，这证实了由于质子化而存在负溶剂化变色现象。强烈的溶剂依赖性光物理和电化学性质，包括激基缔合物发射最大的显著位移，反映了通过氢键和π-堆积相互作用介导的自组装，使低聚物成为各种光传感应用的潜在候选物。
