Synthesis of controlled π-extended conjugate nanostructures of 1,1′-ferrocene

Synthesis of the (E,E)-1,1′-ferrocene nanostructures having controlled π-extended conjugation was satisfactory carried out starting of 1′-[2-(1,3-dioxolan)]-1-formylferrocene (1). The molecular unit (E)-1′-[2-(1,3-dioxolan)]-1-[β-(p-iodophenyl)ethenyl]ferrocene (2), was obtained in excellent yield by treatment of 1 with p-iodobenzyl triphenylphosphonium ylid followed by Z→E isomerization, catalyzed by iodine, in quantitative yield. Compound (E)-2 was transformed in (E)-1′-{2-(1,3-dioxolan)-1-[β-[4-(3-hydroxy-3-methyl-but-1-ynyl)-phenyl]-ethenyl}ferrocene, (E)-4, by palladium catalyzed cross-coupling with 2-methyl-but-3-yn-2-ol. (E)-4 gives (E)-1-[β-(4-ethynylphenyl)-ethenyl]-1′-[2-(1,3-dioxolan)]ferrocene (E)-5 by powder sodium hydroxide treatment. The molecular unit (E,E)-1-{β-[4-(β-(1′-formylferrocenyl)-ethenyl)-phenylethynyl]-phenyl]-ethenyl}-1′-formylferrocene, (E,E)-6, was synthesized by palladium catalyzed cross-coupling between the p-iodophenyl derivative (E)-2 and their ethynyl derivative (E)-5, in good yield. The (E,E)-1,1′-(p-iodophenyl)ethenyl ferrocene, (E,E)-7, was synthesized by reaction between 1,1′-diformylferrocene and the p-iodobenzyltriphenylphosphonium ylid, as a mixture of isomers which were purely isolated. Moreover, isomerization of the Z,Z and E,Z mixture to the E,E isomer, was induced by sunlight exposure, catalyzed by iodine, in quantitative yield. The (E,E)-1,1′-[β-(4-ethynylphenyl)-ethenyl]ferrocene, (E,E)-10, was synthesized in good yield, by palladium catalyzed cross-coupling of compound (E,E)-7 with 2-methyl-but-3-yn-2-ol, followed by powder sodium hydroxide treatment.