Synthesis and Characterization of [5]Cycloparaphenylene
摘要:
The synthesis of highly strained [5]cycloparaphenylene ([5]CPP), a structural unit of the periphery of C-60 and the shortest possible structural constituent of the sidewall of a (5,5) carbon nanotube, was achieved in nine steps in 17% overall yield. The synthesis relied on metal-mediated ring closure of a triethylsilyl (TES)-protected masked precursor 1c followed by removal of the TES groups and subsequent reductive aromatization. UV-vis and electrochemical studies revealed that the HOMO-LUMO gap of [5]CPP is narrow and is comparable to that of C-60, as predicted by theoretical calculations. The results suggest that [5]CPP should be an excellent lead compound for molecular electronics.
The synthesis of highly strained [5]cycloparaphenylene ([5]CPP), a structural unit of the periphery of C-60 and the shortest possible structural constituent of the sidewall of a (5,5) carbon nanotube, was achieved in nine steps in 17% overall yield. The synthesis relied on metal-mediated ring closure of a triethylsilyl (TES)-protected masked precursor 1c followed by removal of the TES groups and subsequent reductive aromatization. UV-vis and electrochemical studies revealed that the HOMO-LUMO gap of [5]CPP is narrow and is comparable to that of C-60, as predicted by theoretical calculations. The results suggest that [5]CPP should be an excellent lead compound for molecular electronics.
Practical Synthesis of [<i>n</i>]Cycloparaphenylenes (<i>n</i>=5, 7-12) by H<sub>2</sub>SnCl<sub>4</sub>-Mediated Aromatization of 1,4-Dihydroxycyclo-2,5-diene Precursors
synthesized in greater than 0.3 g scale. 119Sn NMR spectroscopy clarifies the in situ formation of an atecomplex, H2SnCl4, upon mixing a 2:1 ratio of HCl and SnCl2, which serves as a highly active reducing agent under nearly neutral conditions. When more than 2 equivalents of HCl, in relation to SnCl2, are used, acid‐catalyzed decomposition of the CPP precursors takes place. The stoichiometry of HCl and SnCl2