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

Abstract

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.