Aggregation of One‐Dimensional Wires: The Case of Long Oligoynes.

We show an unexpected aggregation phenomenon of a long oligoyne (Py[16]) with 16 contiguous triple bonds and endcapped with bulky 3,5‐bi(3,5‐bis‐tert‐butylphenyl)pyridine groups. Aggregation of 1D π‐conjugated oligoyne chains is rare given the minimal π–π intermolecular interactions as well as its flexibility that works against self‐assembly. In dilute solutions, the reversible aggregation of Py[16] initiates at low temperature in the range of 140–180 K, and is not observed for shorter oligoynes in this series. Cryogenic UV/Vis electronic absorption spectra and vibrational Raman spectra with different laser wavelength lines tuning from in‐resonance to off‐resonance conditions have been used to extract the vibrational features characterizing the monomer and aggregate species. Theoretical calculations complement the spectroscopic findings. [ABSTRACT FROM AUTHOR]