Beyond p ‐Hexaphenylenes: Synthesis of Unsubstituted p ‐Nonaphenylene by a Precursor Protocol
| Autor: | Jan Freudenberg, Uwe H. F. Bunz, Christian Melzer, Klaus Müllen, Rainer Bäuerle, Daniel Jänsch, Ali Abdulkarim, Hans Joachim Räder, Annemarie Pucci, Marvin Nathusius, Sebastian Beck, Karl-Philipp Strunk |
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| Rok vydání: | 2020 |
| Předmět: |
pi interaction
Infrared 010402 general chemistry 01 natural sciences Oligomer oligo-para-phenylene Catalysis chemistry.chemical_compound Spectroscopy Oligophenylenes | Hot Paper chemistry.chemical_classification Full Paper 010405 organic chemistry Organic Chemistry Intermolecular force Aromatization General Chemistry Polymer Full Papers 0104 chemical sciences Crystallography Molecular geometry chemistry precursor route Cis–trans isomerism conjugation |
| Zdroj: | Chemistry – A European Journal Chemistry (Weinheim an Der Bergstrasse, Germany) |
| ISSN: | 1521-3765 0947-6539 |
| DOI: | 10.1002/chem.202001531 |
| Popis: | 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 (9PPs) 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 13C 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. Unsubstituted para ‐nonaphenylenes were prepared via thermal aromatization of cyclohexadienylene precursors in thin films. The greenish fluorescence of the material is caused by pronounced aggregation in the solid state, in which electronic couplings leads to formation of H‐type aggregates. The emission bands of this small‐molecule are similar with respect to its polymer analogue. |
| Databáze: | OpenAIRE |
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