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Beyond p ‐Hexaphenylenes: Synthesis of Unsubstituted p ‐Nonaphenylene by a Precursor Protocol
Author(s) -
Abdulkarim Ali,
Nathusius Marvin,
Bäuerle Rainer,
Strunk KarlPhilipp,
Beck Sebastian,
Räder Hans Joachim,
Pucci Annemarie,
Melzer Christian,
Jänsch Daniel,
Freudenberg Jan,
Bunz Uwe H. F.,
Müllen Klaus
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202001531
Subject(s) - oligomer , chemistry , polymer , polymer chemistry , solid state , intermolecular force , aromatization , mass spectrometry , nuclear magnetic resonance spectroscopy , thermal stability , crystallography , molecule , stereochemistry , organic chemistry , catalysis , chromatography
The synthesis of unsubstituted oligo‐ para ‐phenylenes ( OPP ) exceeding para ‐hexaphenylene—in the literature often referred to as p ‐sexiphenyl—has long remained elusive due to their insolubility. We report the first preparation of unsubstituted para ‐nonaphenylenes ( 9PP s) by extending our precursor route to poly‐ para ‐phenylenes ( PPP ) to a discrete oligomer. Two geometric isomers of methoxylated syn ‐ and anti ‐cyclohexadienylenes were synthesized, from which 9PP was obtained via thermal aromatization in thin films. 9PP was characterized via optical, infrared and solid‐state 13 C NMR spectroscopy as well as atomic force microscopy and mass spectrometry, and compared to polymeric analogues. Due to the lack of substitution, para ‐nonaphenylene, irrespective of the precursor isomer employed, displays pronounced aggregation in the solid state. Intermolecular excitonic coupling leads to formation of H‐type aggregates, red‐shifting emission of the films to greenish. 9PP allows to study the structure–property relationship of para ‐phenylene oligomers and polymers, especially since the optical properties of PPP depend on the molecular shape of the precursor.