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 (V) 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 V values. 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 V range 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.

Self‐Assembled α‐Cyanostilbenes for Advanced Functional Materials

“…Depending on the experimental process, aggregates in colloidal solution or suspensions, or matrix‐dispersions can be achieved. Interestingly, some experimental methods, such as emission spectroscopy or fluorescence microscopy, that exploit the emissive abilities of CS‐blocks have allowed the observation and control of the assembly processes and enabled the interactions in the assemblies to be evaluated. [117a]…”

Emission and Color Tuning of Cyanostilbenes and White Light Emission

“…17,19−25 Among many known derivatives, there is an active interest toward materials exhibiting unique aggregation-induced emission (AIE or AIEE) for their excellent emissive properties in the solid or aggregated state due to restricted molecular rotations with subsequent reduction of radiationless decay processes. 26−29 α-Cyanostilbenes belongs to one such class of π-conjugated substrates that exhibit this unique emission behavior and were widely utilized for optical and biological applications. 30−35 Cyanostilbenes are considered to be an attractive platform as different chemical entities can be synthetically incorporated in the core structure in the form of the donor (D) or acceptor (A) groups and other functional moieties via routine synthetic procedures.…”

Real‐Time Fluorescence Visualization of Nanoparticle Aggregation and the Polymorph‐Transition Process of a Mechanofluorochromic Difluoroboron‐β‐Diketone Derivative

“…Figure 1d shows the fluorescence lifetime changes as a function of time after reprecipitation. [15] The simulated results were shown in the SI (FigureS4). The mean fluorescence lifetime (τ avg ) was 35.8 ns immediately following the precipitation, which decreased over time (after 60 min, τ avg was 12.5 ns).…”