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The Competitive Aggregation Pathway of an Asymmetric Chiral Oligo( p ‐phenyleneethynylene) Towards the Formation of Individual P and M Supramolecular Helical Polymers
Author(s) -
Fernández Zulema,
Fernández Berta,
Quiñoá Emilio,
Freire Félix
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202100162
Subject(s) - supramolecular chemistry , diastereomer , polymer , chemistry , crystallography , solvent , toluene , supramolecular polymers , stereochemistry , polymer chemistry , crystal structure , organic chemistry
A complex aggregation pathway towards two diastereomeric P and M supramolecular helices arises from the aggregation of a short, chiral, and rigid oligo(phenyleneethynylene) [OPE, ( S )‐ 1 ]. Thus, while Agg I aggregate is obtained when a DCM solution of ( S )‐ 1 is diluted with MCH at room temperature, Agg II aggregate is generated only after a slow heating (353 K)/cooling (273 K) process. Interestingly, during Agg I formation (mechanism 1), short P chain oligomers are produced, which have a great tendency to aggregate in plane, yielding brick‐like nanostructures that halt the aggregation process. On the other hand, after a heating/cooling cycle, long M type columnar helical aggregates ( Agg II ) are obtained, formed by individual supramolecular polymer chains (mechanism 2) easily visualized by AFM. The two different P / M orientations obtained for Agg I and Agg II reveal the dynamic character of the system and its ability to create diastereomeric helical structures under the right conditions. Different experimental protocols were explored to prepare long M type columnar helical aggregates, which are not obtained by using the previous MCH/DCM 99/1 (v/v) solvent mixture. The generation of the desired M oriented supramolecular polymer is achieved when toluene is added to the solvent mixture in a 97/2/1 MCH/Tol/DCM (v/v/v) ratio.