Department of Chemistry, University of South Dakota, Vermillion, South Dakota 57069, United States.
J Org Chem. 2011 Oct 7;76(19):7866-71. doi: 10.1021/jo2013143. Epub 2011 Sep 8.
Site-selective imination of anthraquinone-based macrocyclic crown ethers using titanium tetrachloride as the catalyst yields imines where only the external carbonyl group of the anthraquinone forms Schiff-bases. The following aromatic amines yield monomeric compounds (aniline, 4-nitroaniline, 4-pyrrolaniline, and 1,3-phenylenediamine). Reaction of 2 equiv of the macrocyclic anthraquinone host with 1,2- and 1,4-phenylenediamine yields dimeric imine compounds. The 1,2-diimino host acts as a luminescence sensor, exhibiting enhanced selectivity for Ba(II) ion. Spectroscopic data indicate that two barium ions coordinate to the sensor. Due to E/Z isomerization of the imine, the monomeric complexes are nonluminescent. Restricted rotation about the 1,2 oriented C═N groups or other noncovalent/coordinate-covalent interactions acting between neighboring crown ether rings may inhibit E/Z isomerization in this example, which is different from current examples that employ coordination of a metal cation with a chelating imine nitrogen atom to suppress E/Z isomerization and activate luminescence. The 1,4-diimino adduct, where the crown rings remain widely separated, remains nonluminescent.
使用四氯化钛作为催化剂，对蒽醌基大环冠醚进行选择性亚胺化，只有蒽醌的外部羰基形成席夫碱。以下芳香胺生成单体化合物（苯胺、4-硝基苯胺、4-吡咯烷苯胺和 1,3-苯二胺）。与 2 当量的大环蒽醌主体与 1,2-和 1,4-苯二胺反应，生成二亚胺化合物。1,2-二亚氨基主体作为发光传感器，对钡(II)离子表现出增强的选择性。光谱数据表明，两个钡离子与传感器配位。由于亚胺的 E/Z 异构化，单体配合物是非发光的。由于 1,2 定向 C═N 基团的受限旋转或相邻冠醚环之间的其他非共价/配位共价相互作用，可能会抑制本例中的 E/Z 异构化，这与当前采用金属阳离子与螯合亚胺氮原子配位来抑制 E/Z 异构化并激活发光的例子不同。1,4-二亚胺加合物中，冠环仍然相距很远，保持非发光。
