Preparation of dendrimers with cooperated functional groups.

点击翻译按钮获取中文摘要

1. Snowflake-shaped porphyrin dendrimers with and without anthraquinonyl terminals (AQ) were prepared. Highly efficient intramolecular singlet energy-transfer from the branching chains or conjugated chains to the Zn porphyrin core was observed in dendrimers. When the Zn porphyrin core in the dendrimer with AQ was excited in degassed THF, the intensity of the Zn porphyrin florescence decreased to 31% compared to dendrimer without AQ. The degree of fluorescence quenching is more remarkable in polar solvent. These results suggest that the fluorescence quenching in the dendrimer with AQ is attributable to the intramolecular electron-transfer from the Zn porphyrin core to AQ. Comparison of the relative fluorescence intensity with reference compound suggested that the remarkable enhancement of the electron-transfer rate by dendritic architectures.2. Novel dendrons containing both flexible side chains and a rigid conjugated chain were prepared. Bipyridine units were incorporated at the end of the rigid conjugated chain as well as the flexible branched chains to control the conformation of the branching chains by a metal complexation. The dendron formed 1:1 iron(II) complexes in chloroform-methanol (1:1) at room temperature.3. A covalently linked assembly of the five snowflake-shaped dendrimers was prepared. The snowflake-shaped dendrimers with an iodo and three phenyl terminals (AB3-type) and with four ethynyl terminals at the end of conjugated chains (A4-type) served as key building brocks for the pentamer. Sonogashira coupling reaction of the A3B-type dendrimer with the A4 dendrimer afforded the desired pentamer in 19% yield. The pentamer was unambiguously characterized by means of NMR and MALDI-TOF mass spectroscopy. UV-Vis and fluorescence spectroscopy suggested intramolecular singlet energy transfer from the four peripheral zinc porphyrin units to the free base porphyrin core.