Gram-Scale Syntheses and Conductivities of [10]Cycloparaphenylene and Its Tetraalkoxy Derivatives.

[10]Cycloparaphenylene ([10]CPP) and its tetraalkoxy derivatives were synthesized on the gram scale in 7 steps starting from 1,4-benzoquinone or 2,5-dialkoxy-1,4-benzoquinone. The key steps involve the highly cis-selective bis-addition of 4-bromo-4'-lithiobiphenyl to the quinones to produce a five-ring unit containing cyclohexa-1,4-diene-3,6-diol moiety, the platinum-mediated dimerization of the five-ring unit, and the H2SnCl4-mediated reductive aromatization of cyclohexadienediol. The tetraalkoxy substituents increased the solubility of [10]CPP in common organic solvents. The carrier-transport properties of thin films of [10]CPP and its derivatives were measured for the first time and indicated that [10]CPP derivatives could rival phenyl-C61-butyric acid methyl ester, which is used widely as an n-type active layer in bulk heterojunction photovoltaics.