Optical Properties And Assembly Structures Of Luminescent Molecules Induced By Chiral Aggregation

In this thesis,by modification of excellent fluorescent scaffold with amino acid attachments,a series of chiral fluorescent molecules were synthesized.Systematic research is carried out to study the optical properties,thermal stability and self-assembling behaviors.There were three parts in this thesis1.By modifying excellent luminescence molecules?phenanthro[9,10-d]imidazole,PIM?with alanine connected to the C₂ position,we synthesized chiral molecules C₂-PIM-D-Ala and C₂-PIM-L-Ala.The molecular structures were determined by nuclear magnetic resonance?NMR?,mass spectroscopy and elemental analysis.The chirality of the molecules was characterized by circular dichroism spectra and they showed mirror absorption,suggesting that their chirality was determined by Alanine attachments.Both molecules had aggregation induced emission enhancement?AIEE?and they also had circularly polarized luminescence?CPL?with the asymmetric factor⁰.01.Thermogravimetric analysis and differential scanning calorimetry suggested that they had excellent thermo stability.The incorporation of Alanine also endowed the molecules with the ability to self-assemble.Fluorescence microscope,scanning electron microscope and atomic force microscope?AFM?revealed that helical fibers were formed.2.By modifying PIM scaffold with alanine connected to the N₁ position,we synthesized chiral molecules N₁-PIM-D-Ala and N₁-PIM-L-Ala.In contrast to the AIEE molecule C₂-PIM-Ala,N₁-PIM-Ala was an ACQ molecule,suggesting that different locations of alanine attachment considerably affected the optical property of PIM.The thermodynamic data of N₁-PIM-Ala was similar to that of C₂-PIM-Ala and it showed that the location of alanine methyl ester make no difference to thermo stability.3.By modifying FAS and DPAS with alanine,FAS-L-Ala and DPAS-L-Ala weresynthesized with property of?excited-state intermolecular proton transfer,ESIPT?.FAS-L-Ala was nearly plane with the two phenyl groups locked together,while DPAS-L-Ala had a propeller shape with the two phenyl groups at free rotation state.Thus,DPAS-L-Ala had more significant AIEE property because the phenyl rings efficiently restricted the rotation of the molecules when they aggregated.The molecules also showed typical ESIPT characteristics that they had two emission peaks,which changed alternately upon the addition of different polar solvent.The molecules had obvious p H effect and were specific to cupric ion.They also had the ability to self-assemble into luminescent fibers as revealed by fluorescence microscope,atomic force microscope?AFM?and scanning electron microscope?SEM?.