Inoue Michiko B., Medrano Felipe, Inoue Motomichi, Raitsimring Arnold, Fernando Quintus
CIPM, Universidad de Sonora, Apartado Postal 130, Hermosillo, Sonora, Mexico, and Department of Chemistry, University of Arizona, Tucson, Arizona 85721.
Inorg Chem. 1997 May 21;36(11):2335-2340. doi: 10.1021/ic9614374.
A condensation reaction between ethylenediaminetetraacetic dianhydride and p-xylenediamine gave a new chelating cyclophane, 3,10,21,28-tetraoxo-5,8,23,26-tetrakis(carboxymethyl)-2,5,8,11,20,23,26,29-octaaza[12.12]paracyclophane, abbreviated as (32edtaxan)H(4), which has three types of electron-donor groups, i.e., amine, carboxylate, and amide groups. The formation of the cyclophane has been confirmed by a single-crystal X-ray analysis of its Zn(2+) complex, [Zn(2)(32edtaxan)].7.5H(2)O, which crystallized in the monoclinic space group P2(1)/c with a = 19.818(1) Å, b = 13.169(1) Å, c = 18.134(1) Å, beta = 104.491(6) degrees, and Z = 4. Each cyclophane molecule coordinates two Zn(2+) ions and results in the formation of a binuclear chelate molecule. The coordination geometry around each metal ion is distorted octahedral, the donor atoms being two carboxylate oxygen atoms, two amine nitrogen atoms, and two amide oxygen atoms. The new cyclophane exhibited a well-defined fluorescence band at 290 nm with 210 nm excitation. The emission intensity was markedly increased in the Zn(2+) complex, in which the coordination of Zn(2+) ions increases the rigidity of the cyclophane leading to a high fluorescence quantum yield. When the cyclophane was coordinated to Cu(2+) ions, the molar absorptivity of a pi-pi transition band observed at 260 nm was increased by a factor of about 10. Such a large spectral change was not observed for the Zn(2+) and Ni(2+) complexes. In the Cu(2+) complex, the two phenyl rings of the cyclophane are expected to be brought closer, as a result of the coordination of deprotonated amide nitrogens to the central metal ion. This allosterism via ring contraction is responsible for the novel behavior of the absorption spectrum. The emission band of the cyclophane was weakened by coordination of copper and nickel as a result of fluorescence quenching caused by a photo-induced electron transfer.
乙二胺四乙酸二酐与对苯二胺之间的缩合反应生成了一种新的螯合环番，即3,10,21,28 - 四氧代 - 5,8,23,26 - 四（羧甲基）- 2,5,8,11,20,23,26,29 - 八氮杂[12.12]对环番，简称为(32edtaxan)H(4)，它具有三种电子供体基团，即胺基、羧基和酰胺基。通过对其锌（II）配合物[Zn(2)(32edtaxan)].7.5H(2)O进行单晶X射线分析，证实了该环番的形成，该配合物在单斜空间群P2(1)/c中结晶，a = 19.818(1) Å，b = 13.169(1) Å，c = 18.134(1) Å，β = 104.491(6)°，Z = 4。每个环番分子配位两个锌（II）离子，形成双核螯合分子。每个金属离子周围的配位几何形状为扭曲八面体，供体原子为两个羧基氧原子、两个胺基氮原子和两个酰胺氧原子。这种新的环番在210 nm激发下，在290 nm处呈现出明确的荧光带。在锌（II）配合物中，发射强度显著增加，其中锌（II）离子的配位增加了环番的刚性，导致高荧光量子产率。当环番与铜（II）离子配位时，在260 nm处观察到的π - π跃迁带的摩尔吸光系数增加了约10倍。对于锌（II）和镍（II）配合物，未观察到如此大的光谱变化。在铜（II）配合物中，由于去质子化酰胺氮与中心金属离子的配位，环番的两个苯环预计会靠得更近。这种通过环收缩的变构作用导致了吸收光谱的新行为。由于光诱导电子转移引起的荧光猝灭，环番的发射带因铜和镍的配位而减弱。
