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Optimized synthesis of thermally stable axially modified pyrazine-acene nanoribbon with gelation properties

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Abstract

In this paper, we explored comprehensive synthetic approaches to axially substituted N-heteroacene based nanoribbon with 11 linearly annulated rings. Although synthetically tedious, we found that a stepwise cyclization between α-diketone and o-aromatic diamine to grow nanoribbon is more efficient than simultaneous dicylization in one step using 3,6-disubstituted-1,2,4,5-tetraaminobenzene. In addition, for the axial modification, pre-modification of a building block was superior to post-modification of preformed nanoribbon. The nanoribbon was characterized with UV-Vis spectroscopy, CV, DSC, and TGA. The nanoribbon showed a relatively stabilized ELUMO of −3.74 eV due to the electron-deficient nature of the core and reduced Egap of 1.55 eV as a result of intramolecular charge transfer between the core and axial thiophene. The electronic properties were also investigated with theoretical calculations at B3LYP/6-31G* level of theory/basis set. Particular attention was paid to the distribution of frontier molecular orbitals as these correlated with the measured electronic properties. The title nanoribbon exhibited remarkable thermal stability with a 424 °C decomposition temperature at 5% weight loss. The axially substituted nanoribbon showed excellent one-dimensional fibrillation properties via organogelation. The nanoribbon gelled hydrocarbon solvents and select halogenated solvents with the lowest critical gelation concentration of 1.2 mM in hexadecane. FE-SEM confirmed the existence of endless flexible one-dimensional fibers with a thickness of ca. 200 nm. Despite the large π-core, the axial functionalization imparted not only processability but also self-assembly ability while maintaining excellent thermal stability. These properties would be useful in future optoelectronic applications.

Graphical abstract: Optimized synthesis of thermally stable axially modified pyrazine-acene nanoribbon with gelation properties

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Article information


Submitted
19 Dec 2019
Accepted
05 Feb 2020
First published
05 Feb 2020

New J. Chem., 2020, Advance Article
Article type
Paper

Optimized synthesis of thermally stable axially modified pyrazine-acene nanoribbon with gelation properties

S. H. Lee, M. S. Valverde Paredes, T. J. Rappenecker, K. A. Robins and D. Lee, New J. Chem., 2020, Advance Article , DOI: 10.1039/C9NJ06303J

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