Synthesis And Supramolecular Assembly Properties Of Novel Functional BODIPY-Type Molecules

Supramolecular polymerization is a process in which molecular building blocks form ordered aggregate through non-covalent interactions,such as hydrogen bonding,?-?stacking,hydrophobic interaction and van der Waals force.As one of the most outstanding functional dyes,BODIPY dye has been extensively applied in biological detection and nanomaterials fields for their excellent spectral property and good stability.The aim of this work is to design and synthesize novel BODIPY molecules and study systematically the thermodynamics and dynamics of self-assembly and the structures of supramolecular aggregates,and those studies could lay the foundation for further application.The specific research contents of this paper are as follows:(1)An aza-BODIPY molecule bearing tridodecyloxy benzamide pendants-triazole linkages was designed and synthesized by“click”reaction.Living supramolecular polymerization behaviour of the aza-BODIPY molecule was demonstrated based on biphasic aggregation pathways taking advantage of the interplay between intramolecularly H-bonded and intermolecularly H-bonded conformers.The results revealed that the metastable aggregate(Agg.I)could be successfully obtained via the rapid cooling of the hot methyl cyclohexane solution of monomers.In contrast,the aggregate(Agg.II)with thermodynamic stability was obtained by slowly cooling of the solution.In the morphological studies,the nanoparticles of Agg.I and nanofibers of Agg.II observed by AFM,TEM and SEM imaging.Aggregation mechanisms and packing patterns of Agg.I and Agg.II were investigated by temperature-dependent ¹H NMR,UV-Vis absorption spectroscopy,IR spectroscopy and SXRD.The kinetic study indicates that the transformation from Agg.I to Agg.II can be realized by either thermal transformation or seeded supramolecular polymerization.Based on the above research,the living supramolecular polymerization of Agg.I seeded by the Agg.II seeds at different temperatures were designed and conducted.The phenomenon about the significant deviation between initial rate of supramolecular polymerization cycles and the trend predicted by the law of“decrease by half”was observed,and its possible reason was analyzed.(2)The supramolecular polymerization of aza-BODIPY molecule in the mixed solvent of MCH/TOL was systematically studied.The metastable aggregates I of aza-BODIPY molecule in the mixed solvent of MCH/TOL were trapped kinetically,and transformed to thermodynamically stable aggregates II at high temperatures.The chiral supramolecular aggregates(Agg.H)were formed by increasing the proportion of TOL in the mixed solvent.The transformation of Agg.I in the mixed solvent(V_MCH/V_TOL=2/1)was induced by either non-chiral aggregate seeds(seed _Agg._II)or chiral supramolecular aggregate seeds(seed _Agg.H).The cooling-heating cycles for supramolecular polymerization were monitored by UV-Vis absorption spectroscopy and fitted with the nucleation-growth model,which finally revealed that the critical aggregation temperature of chiral supramolecular aggregates is much lower than that of ordinary aggregates.The results confirmed that the chiral aggregates were more stable than the achiral fibrous Agg.II.The living supramolecular polymerization of metastable aggregates successfully induced by chiral supramolecular aggregate seeds.(3)The supramolecular polymerization of aza-BODIPY molecules in chiral solvents was studied.The following conclusions were obtained by the research of UV-Vis absorption spectrum,circular dichroism and TEM:common fibrous aggregates can be formed in achiral limonene solution by aza-BODIPY molecules,and chiral fiber supramolecular aggregates can be formed in chiral limonene solution.Right-handed aggregates of aza-BODIPY with negative cotton effect were formed in(R)-(+)-Limonene solution,and more stable than helix fibrous aggregates in(S)-(-)-Limonene solution for the lower aggregation temperature and aggregation rate.(4)The amphiphilic BODIPY quaternary ammonium molecule bearing three hydrophobic dodecyl chains and two hydrophilic quaternary ammonium groups was designed and synthesized,and the aggregates of this compound could be formed in aqueous solution.Upon cooling the solution of dye molecules with different rates,metastable Agg.I and thermodynamic stable Agg.II could be formed through different aggregation pathways.Both Agg.I and Agg.II exhibit aggregation-induced enhanced emission(AIEE)phenomenon,and the quantum yields of aggregate I and aggregate II increased to 3.1 times and 4.4 times of that of monomer,respectively.Thus,AIEE properties of BODIPY molecules could be controlled by the dynamical pathways of supramolecular aggregation.The transformation of metastable aggregate achieved by thermal transformation or seeded supramolecular polymerization.