Nickel-Ion-Coordinated Reversibly Solvatochromic Polydiacetylene Based on Tubular Assembly of Macrocyclic Diacetylene
Bubsung Kim, Mohammed Iqbal Khazi, Jong‐Man Kim
Abstract
Polydiacetylenes (PDAs) present excellent chromogenic characteristics and have been extensively utilized as a sensory polymeric material to design and fabricate colorimetric sensor systems. Herein, we describe a Ni2+-ion-directed reversibly solvatochromic tubular PDA based on macrocyclic diacetylene (MCDA). A dimeric MCDA complex was formed through Ni2+-intercalated coordinative binding with carboxyl groups, which later transform into blue-phase PDA upon UV irradiation. Infrared spectral analysis confirmed the presence of structural water molecules coordinating to central Ni2+, which predicted to fulfill the octahedral geometry. Spectroscopic studies for the reversible blue–red chromatic behavior revealed a very unusual and unprecedented chromatic switching mechanism originating due to localized structural disruption at the Ni2+ coordination site that leads to torsion in the π-conjugated backbone for chromatic changes, in contrast to the typical residual monomeric dissolution-induced mechanism. This unusual behavior can be attributed to the coordinating water molecules, which presents an attractive advantage by creating a hydrophilic pocket at the coordination site and allows interactions with hydrophilic solvents causing structural distortion.