Proton-Gradient-Driven Self-Assembly of Porphyrin and In Situ Dynamic Analysis in a Microflow Platform

Abstract

Despite rapid advances in supramolecular chemistry, only limited attention has been paid to regulating the self-assembling field, such as by studying diffusional dynamics or the hydrodynamic properties of the solvents that always surround the self-assembling molecules. Herein, we demonstrate that a proton gradient generated in laminar flow can facilitate the acid-base reaction, leading to effective self-assembly of TPPS, a type of porphyrin. In situ fluorescence microspectroscopies reveal that the acid-base reaction followed by self-assembly of TPPS proceed under a uniform diffusional environment in the laminar flow, leading to the creation of discrete J-aggregate fibers (length dispersity Lw/Ln <1.2). Furthermore, we can successfully evaluate the time required for nucleation to be 2.9 ms. In sharp contrast to conventional solution chemistry, the nucleation process of TPPS finishes at a much earlier stage, implying that nucleation might no longer be the rate-determining step in laminar flow. The present self-assembly system in laminar flow provides a way to create a variety of supramolecular architectures under reproducible kinetic conditions, and a comprehensive strategy to construct a kinetic database for self-assembly dynamics.