Stimuli-Responsive Room-Temperature N-Heteroacene Liquid: In Situ Observation of the Self-Assembling Process and Its Multiple Properties

A novel stimuli-responsive room temperature photoluminescent liquid 1 based on N-heteroacene framework is developed and analyzed by several experiments such as differential scanning calorimetry, X-ray diffraction, dynamic viscoelasticity measurement, in situ observation by optical and polarized optical microscope, UV-vis absorption and fluorescent spectroscopy, and by theoretical methods such as ab initio calculation and molecular dynamics computer simulation technique. In contrast to stimuli-responsive solid materials reported previously, liquid 1 in response to HCl vapor as single stimulus can involve dramatically multiple changes in physical properties such as rheological behavior, morphology, as well as photoluminescence. The present ab initio calculation and microsecond-timescale molecular dynamics (MD) simulations reveal that the complexation of 1 and HCl molecules induces a large dipole moment, leading to a formation of stacking structures due to their dipole-dipole interaction. Upon exposure to HC...