Construction of snowflake-shaped dendritic covalent assemblies with rigid conjugated networks.
A convergent method for the construction of shape-persistent nanoscale assemblies with conjugated backbones was developed. The copper-free Sonogashira coupling reaction was successfully applied to the formation of multiple covalent connections between conjugated terminals (iodide substituted aryl groups) of AB(2)-type outer components and four conjugated terminals (acetylenic bonds) of an inner A(4)-type core dendrimer. The conjugated networks in the starting components are expanded during the assembly process to afford nanoscale dendritic conjugated networks of the type A(4)(AB(2))(4), which have a porphyrin core, and longer (3.9 or 4.5 nm) and shorter (1.6 nm) conjugated chains. Fluorescence measurements revealed that singlet energy is effectively transferred in the assemblies from peripheral benzyl ether units and conjugated chains to the free base porphyrin core.
Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 Japan. kozaki@sci.osaka-cu.ac.jp
Masatoshi
M
Kozaki
Shirou
S
Morita
Shuichi
S
Suzuki
Keiji
K
Okada