|
内容記述 |
Supramolecular polymerization of π-extended compounds with hydrogen-bonding sites remains challenging, especially in high concentrations, due to their limited solubility in nonpolar solvents. Herein, we report an indirect method incorporating a thermal precursor approach for the supramolecular polymerization of a poorly soluble tetrabenzoporphyrin (BP) derivative with multiple hydrogen-bonding sites and chiral cholesterol groups (BPChol). Polymerization in the nonpolar solvent tetralin is induced by a retro-Diels–Alder reaction of the highly soluble precursor (CPChol) to BPChol in the hot solution, followed by natural cooling, as confirmed by monitoring absorption spectra. The emergence of circular dichroism signals in the BP absorption regions corroborates the formation of aggregates with supramolecular chirality, as the first chiroptical characterization of BP aggregates. Detailed structural analyses using high-resolution microscopies reveal a unique pyramidal multilayer structure with a spiral nature. Additionally, faster cooling produces monolayer nanosheets, which differ from the multilayer structures formed upon natural cooling. This is due to a different nucleation process in the cooperative polymerization. By using the nanosheets as seeds, seed-induced polymerization into extended sheets is confirmed. Notably, the indirect precursor method using CPChol allows polymerization at high concentrations (mM level) to afford the micro-sized pyramids, never obtained by the direct method using BPChol. |
