Optically Pure, Monodisperse cis-Oligodiacetylenes: Aggregation-Induced Chirality Enhancement

Authors


  • Funding from the University of Erlangen-Nuremberg, the Cluster of Excellence “Engineering of Advanced Materials” at the University of Erlangen-Nuremberg, the Deutsche Forschungsgemeinschaft (DFG; SFB 953: “Synthetic Carbon Allotropes”), the Interdisciplinary Center for Molecular Materials (ICMM), and the Bavarian Academy of Science is gratefully acknowledged.

Abstract

Conformational changes in the conjugated backbone of poly- and oligodiacetylenes (PDAs and ODAs) play an important role in determining the electronic properties of these compounds. At the same time, conformational changes can also result in a folded structure that shows helical chirality. Using D-camphor as a chiral building block, we have designed a high-yielding, iterative synthesis of monodisperse, optically pure cis-oligodiacetylenes (ODAs). cis-ODAs up to the tridecamer have been formed, which is the longest monodisperse cis-ODA reported to date. UV/Vis spectroscopy suggests a large effective conjugation length in THF, likely the result of a linear, planar conformation in this solvent. High-resolution STM/AFM measurements of the nonamer cast from THF onto HOPG show a linear structure. In iPrOH, circular dichroism (CD) spectra suggest the formation of chiral aggregates for ODAs with at least nine D-camphor units, based on a strong CD response.

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