Transition Metal (II)/(III), Eu(III), and Tb(III) Ions Induced Molecular Photonic OR Gates Using Trianthryl Cryptands of Varying Cavity Dimension
摘要:
Three heteroditopic cryptands with different cavity dimensions have been synthesized in high yields at 278 K without employing any templating metal ion. The three secondary amino nitrogens in each cryptand could be derivatized with anthryl groups to have a fluorophore-spacer-receptor configuration, The fluorophores in these systems do not show any fluorescence due to an efficient photoinduced intramolecular electron transfer (PET) from nitrogen lone pairs. However, the fluorescence can be recovered to different extents in the presence of different metal ions and protons as well. On complexation by a transition metal ion or on protonation in a solvent like dry THF, each exhibits large fluorescence enhancement as the nitrogen lone pairs responsible for PET are engaged in bonding. Inner-transition-metal ions like Eu(III) or Tb(III) show remarkable discrimination and give high fluorescence enhancement only in one case where the cavity size is smaller than that of other two. Each system exhibits large fluorescence enhancement with Pb(II) among the heavy metal ions studied. The present study shows that transition metal ions and Pb(II), which are known for quenching, can indeed cause fluorescence enhancement in cryptand-based systems. It is also reported for the first time that inner-transition-metal ions can also cause fluorescence. The enhancement in each case is interpreted in terms of a communication gap between the metal ion and fluorophore. Such cryptand-based fluorophores can be useful as potential molecular photonic devices and metal ion sensors as well.
Synthesis, characterization and complexation properties of a heteroditopic cryptand L towards CuII and ZnII: crystal structures of L·3H2O and [ZnL][ClO4]2·2H2O
摘要:
通过三(3-氨基丙基)胺和 2,2′,2″-硝基三(乙烯氧基)三(苯甲醛)的三脚架-三脚架席夫碱缩合,然后用 NaBH 4 原位还原,在 5 ℃ 和无任何模板金属离子的条件下,高产率地合成了一种新的杂二价隐核糖(L)。分子具有内端构象,两个桥头硝基之间的距离为 5.291 Å。这种隐核糖与铜(II)和锌(II)高氯酸盐形成通式为 [ML][ClO 4 ] 2 的单核隐核酸盐。测定了 [ZnL][ClO 4 ] 2 -2H 2 O 的晶体结构。Zn II 以几乎理想的四面体几何形状占据了空腔的 N 4 端。在 298 K 的乙腈溶液中,蓝色的隐色酸铜(II)在 875 和 745 纳米波长处显示出配位体场带,在 275 纳米波长处显示出配位体对金属的电荷转移,这表明存在假四面体 CuN 4 配位。不过,它在固态或溶液中的 EPR 光谱特征是典型的磁浓缩复合物。