title: AIE phenomena of a cyanostilbene derivative as a probe of molecular assembly processes.
abstract: The initial processes of the crystallization of a solute molecule, 1-cyano-trans-1,2-bis-(4'-methylbiphenyl)-ethylene (CN-MBE) in binary solution (water and acetone), were investigated by means of fluorescence spectroscopy as well as scanning electron microscopy (SEM). With an increase in the volume fraction (Vw) of the poor solvent (water) in the solution, a drastic change in the fluorescence spectra and intensity of CN-MBE was observed. This change was attributed to aggregation induced emission (AIE). By analyzing the evolution of AIE by multivariate curve resolution-alternating least squares (MCR-ALS), it was revealed that four main species appeared in the solution depending on the Vwvalues. On the basis of molecular exciton theory, we assigned these four emissive states to the monomer, H-dimer, J-dimer, and H-aggregates. Interestingly, the J-dimer state was observed only in a Vwrange of 40% to 50%, just before the formation of the aggregate. This result suggests that the J-dimer plays an important role as the precursor for larger aggregates leading to crystal formation. By integrating the present results with previous work on the crystallization of CN-MBA through solvent evaporation, we discussed the dynamics of the crystallization from the viewpoint of the sequence of molecular species appearing in the aggregation in solution.
authors.affiliation: Institute of Education, Shinshu University, Nagano 380-8544, Japan. fito@shinshu-u.ac.jp.
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ito
authors.forename: Jun-Ichi
authors.initials: JI
authors.lastname: Fujimori
authors.forename: Narumi
authors.initials: N
authors.lastname: Oka
authors.forename: Michel
authors.initials: M
authors.lastname: Sliwa
authors.forename: Cyril
authors.initials: C
authors.lastname: Ruckebusch
authors.forename: Syoji
authors.initials: S
authors.lastname: Ito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyasaka