Self-Assembled Fibrillar Networks through Highly Oriented Aggregates of Porphyrin and Pyrene Substituted by Dialkyl l-Glutamine in Organic Media^†

Abstract

Microfibrous self-aggregation of chromophoric groups of porphyrin and/or pyrene substituted by didodecyl l-glutamic acid in organic media is confirmed by transmission electron microscopic (TEM) observation. Chromophoric probes of porphyrin and pyrene moieties enable evaluation of their assembling behavior photophysically through UV−vis, circular dichroism (CD), and fluorescence spectroscopic characterization. This spectroscopic characterization was able to compensate the lack of TEM observation for the aggregation even at a low concentration below the critical gel concentration. The temperature affects the salient features of the photophysics of porphyrin or pyrene in the microfibrous assemblies. Highly oriented network structures were formed at low temperature since the CD intensities of the porphyrin and pyrene systems increased with lowering the temperature. Fluorescence spectroscopic characterization confirmed the monomer excitation of porphyrin itself, and efficient excimer formation for the pyrene−pyrene charge transfer was detected at low temperature. In particular, we also obtained the preliminary results of fluorescence spectroscopic measurement on singlet−singlet energy migration from pyrene to porphyrin in the mixed assemblies for mimicry of the efficient energy transfer process of the photosynthetic antenna complex