Porous organic crystals can be used to probe the effects of confinement on reactions including polymerizations. Geometric constraints imposed by the porous crystals and non-covalent interactions influence the structure of the growing polymer, potentially modulating the stereochemistry, tacticity, and alignment of the polymer chains. The Shimizu group utilizes urea hydrogen bonding to direct the assembly small building block such as triphenylamine bis-urea macrocycles 1 into columns affording functional porous organic crystals. These assembled columns contain the solvent of crystallization bound within the channels. Heating the crystals leads to removal of the solvent and activates the host for guest exchange by single-crystal-to-single-crystal transformations. Two different electron accepting molecules were successfully encapsulated inside the activated host 1. While 1-2,5-dichlorobenzoquinone exhibits a charge transfer (CT) transition upon complex formation, the 1-2,1,3-benzothiadiazole complex undergoes a photoinduced electron transfer upon irradiation with 365 nm LEDs. These porous crystals were also used to absorb monomers, including pyrrole (Py) and ethylenedioxythiophene (EDOT), which could be subsequently polymerized inside the host by heating in I2 atmosphere. 13C NMR, FT-IR, Raman and photophysical characterization shows presence of the polymers inside the channel. After dissolution of the host, SEM images of the insoluble polymers demonstrates that the polymers retain the size and morphology of host 1. The properties of these encapsulated polymers and their properties before and after removal from the porous crystals will be presented.

Exploring charge transfer and polymerizations within self-assembled bis-urea macrocycles

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.