School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332-0400, USA.
J Org Chem. 2010 Feb 5;75(3):523-34. doi: 10.1021/jo901961a.
Five new, unsymmetrical 1,4-distyryl-2,5-bisphenylethynylbenzenes (cruciforms, XF) have been prepared by a sequential Horner reaction of the bisphosphonate of 2,5-diiodo-1,4-xylene with two different aromatic aldehydes. The obtained diiodide was coupled to phenylacetylene under Sonogashira conditions with (Ph(3)P)(2)PdCl(2) as catalyst. The resulting XFs carry dibutylamino, pyridyl, cyano, and diphenylamino residues on their styryl arms to give rise to donor-, acceptor-, and donor-acceptor-substituted XFs. The optical properties of these XFs were investigated. Titration studies using trifluoroacetic acid tracked changes in the electronic structure of the XFs upon protonation. Donor XFs display a blue shift in absorption and emission upon protonation, while the pyridyl-substituted XF displays red shift in absorption and emission upon protonation. In the case of the donor-acceptor XF carrying a pyridyl and an aminostyryl arm, the first protonation occurs either on the pyridine or on the dibutylamino arm; a red shift is seen in absorption (for the former) and a blue shift is observed in emission (for the latter). The titration studies indicate that the protonated XFs do not display kinetic photoacidity when operating either in dichloromethane or acetonitrile solutions. The trends observed for protonation were mirrored when the XFs bind to metal cations. While the binding constants of the metal cations to the XFs were lower than for that for protons, as in some cases full metalation of the XF could not be obtained, the results were qualitatively the same. We did not find dynamic excited-state decomplexation events in the XFs that we have investigated. The XFs, stilbene derivatives, are different from other reported, similarly structured fluorophores as they show significant ratiometric changes in emission upon metal complexation; thus, distyrylbenzene-derived fluorophores may be, in the end, viable choices as platforms for metal ion detection.
已经通过双膦酸酯 2,5-二碘-1,4-二甲苯与两种不同的芳醛的顺序 Horner 反应制备了五个新的不对称 1,4-二芳基-2,5-双苯乙炔基苯（十字形，XF）。获得的二碘化物在 Sonogashira 条件下与苯乙炔偶联，使用（Ph(3)P)(2)PdCl(2)作为催化剂。所得的 XF 在其苯乙烯臂上带有二丁氨基、吡啶基、氰基和二苯基氨基残基，从而产生供体、受体和供体-受体取代的 XF。研究了这些 XF 的光学性质。使用三氟乙酸进行的滴定研究跟踪了 XF 的电子结构在质子化时的变化。供体 XF 在质子化时显示出吸收和发射的蓝移，而吡啶取代的 XF 在质子化时显示出吸收和发射的红移。在带有吡啶基和氨基苯乙烯臂的供体-受体 XF 的情况下，第一个质子化发生在吡啶或二丁氨基臂上；在吸收中观察到红移（对于前者），在发射中观察到蓝移（对于后者）。滴定研究表明，质子化的 XF 在二氯甲烷或乙腈溶液中均不显示动力学光酸性。当 XF 与金属阳离子结合时，观察到的质子化趋势得到了反映。虽然金属阳离子与 XF 的结合常数低于与质子的结合常数，但在某些情况下，无法获得 XF 的完全金属化，结果在性质上是相同的。我们没有发现我们研究的 XF 中存在动态激发态去络合事件。XF，二苯乙烯衍生物，与其他报道的类似结构的荧光团不同，因为它们在金属络合时显示出显著的发射比率变化；因此，二苯乙烯衍生的荧光团最终可能是金属离子检测的可行选择。
