Living Supramolecular Polymerization of an Aza-BODIPY Dye Controlled by a Hydrogen-Bond Accepting Triazole Unit Introduced by Click Chemistry.

An aza-BODIPY dye 1 bearing two hydrophobic "fan-shaped" tridodecyloxybenzamide pendants through 1,2,3-triazole linkages was synthesized by "click" reaction and characterized. 1H NMR studies indicated that dye 1 exhibited variable conformations through intramolecular H-bonding interaction, which is beneficial for the polymorphism of aggregation. The thermodynamic, structural, and kinetic aspect for the supramolecular polymerization of dye 1 was investigated by UV/Vis absorption spectroscopy, IR spectroscopy, AFM, TEM, and SEM. The results revealed the biphasic aggregation pathways of dye 1, leading to the formation of off pathway, metastable Agg. I and thermodynamically stable Agg. II with distinct H-aggregation spectra and nanoscale morphology. The living manner of the supramolecular polymerization of dye 1 was demonstrated in seeded polymerization experiments with temperature-modulated successive cooling-heating cycles. Moreover, at temperatures higher than 298 K, the polymerization cycles exhibit distinct kinetic character in contrast to the typical living supramolecular polymerization behaviour at lower temperatures. This observation could be explained by a proposed mechanism in which the accumulative effect of the seeds generated by thermal transformation at high temperatures was considered.