Chirally twisted oligo(phenyleneethynylene) by cyclization with alpha-helical peptide.

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Spectroscopy

Background:

• Helical peptides and oligo(phenyleneethynylene) (OPE) are important molecular building blocks.
• Conjugated systems with chirality are of significant interest for advanced materials.

Purpose of the Study:

• To synthesize and characterize a novel cyclic conjugate of a helical decapeptide and OPE.
• To investigate the conformational and optical properties of the resulting C-OPE10 conjugate.
• To explore the potential for creating main-chain chiral pi-conjugated systems.

Main Methods:

• Synthesis of the cyclic peptide-OPE conjugate (C-OPE10).
• Circular dichroism (CD), absorption, and emission spectroscopies for conformational and optical analysis.
• Time-dependent density functional theory (TD-DFT) molecular simulations.

Main Results:

• Successful synthesis of the C-OPE10 cyclic conjugate.
• Observation of an induced negative Cotton effect in the OPE moiety, indicating a chirally twisted conformation.
• TD-DFT simulations confirmed a right-handed twist in the OPE moiety.

Conclusions:

• The cyclic conjugate C-OPE10 adopts a distorted, chirally twisted conformation.
• This work presents a novel strategy for generating pi-conjugated compounds with inherent main-chain chirality.
• The study provides insights into the optical properties of twisted OPE systems within a cyclic framework.