Reversible Color and Shape Changes of Nanostructured Fibers of a Macrocyclic π‑Extended Thiophene Hexamer Promoted by Adsorption and Desorption of Organic Vapor

A phenyl-substituted
macrocyclic π-extended thiophene hexamer 1, composed
of four thienylene-ethynylene and two thienylene-vinylene
units, has a solid-state structure in which π–π,
CH−π, and van der Waals interactions occur. Slow addition
of acetone to a solution of 1 in CS2 produces
a yellow nanostructured fiber 1-A containing a 1:1.5:1
ratio of 1, acetone, and CS2. Over a 2 min
period at 25 °C, 1-A gradually changes to an orange
fiber 1-B containing a 1:0.5:1 ratio of 1, acetone, and CS2. On exposure to acetone vapor, 1-B regenerates 1-A (vapochromism), and removal
of all solvents from 1-A and 1-B generates
a red-orange fiber 1-C, which upon brief immersion in
acetone/CS2 produces 1-A. Furthermore, 1-C is converted to orange yellow fiber 1-D upon
exposure to acetone vapor for 1 s at 25 °C. Analysis of the horizontal
and vertical profiles of the X-ray diffraction (XRD) patterns shows
that removal of solvent from 1-A reversibly creates 1-B in conjunction with a shape and size change along with
arching.