In this study, we report the synthesis and characterization of three novel âpushâpullâ chromophores, in which multiple phenylenevinylene units are endcapped by ferrocene as donor units and malonate moieties as acceptor units. These chromophores have spectroscopic and electrochemical characteristics which consistently change according to the extension of the conjugated bridge, thus to the variation of the HOMOâLUMO band gap. The 1,3-dicarbonyl units, directly incorporated into the conjugated molecular structures, are able to coordinate Lewis acid-like cations, such as lanthanides, as confirmed by UV/Vis, 1H NMR and cyclic voltammetry studies. The UV/Vis spectroscopic response upon complexation with Sc3+ or Eu3+ as the triflate salts is rather unselective and nonlinear in going from the least to the most Ï-extended chromophore. Binding studies in MeCN, analyzed via equilibrium-restricted factor analysis, give values between log Ka = 1.21 and 3.07 and affirm a 1â:â1 stoichiometry of the host:guest complexes in all cases. On the other hand, cyclic voltammetry reveals a selectivity in the response to Sc3+ coordination over Ln3+ (Eu3+, but also Lu3+ and Er3+ were tested) for the two shorter chromophores, whereas the ligand with the longest Ï-bridge is able to sense Er3+ (ÎE1/2 complexed/uncomplexed chromophore = 20 mV) selectively over the other lanthanides.
在这项研究中,我们报告了三种新型“推-拉”发色团的合成和表征,其中多个
苯乙烯基单元由
二茂铁作为供体单元和
丙二酸酯部分作为受体单元封端。这些发色团具有光谱和电
化学特性,这些特性会随着共轭桥的延伸而变化,从而随着HOMO-LUMO带隙的变化而变化。1,3-二羰基单元直接结合到共轭分子结构中,能够与类似
路易斯酸的阳离子(如
镧系元素)配位,这一点已通过紫外/可见光、1H NMR和循环伏安法研究证实。当与
三氟甲磺酸盐Sc3+或Eu3+配位时,紫外/可见光光谱响应从最少的到最长的Β-延伸发色团,是非选择性和非线性的。通过平衡限制因子分析在MeCN中进行的结合研究给出了log Ka = 1.21至3.07之间的值,并确认在所有情况下,主客体复合物的
化学计量比为1∶1。另一方面,循环伏安法显示,对于两个较短的发色团,Sc3+配位对Ln3+(测试了Eu3+,还测试了Lu3+和Er3+)的反应具有选择性,而具有最长Β-桥的
配体能够比其他��