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Structural Control of the Molecular Packing and Dynamics of Mechanofluorochromic Materials Based on Small Donor–Acceptor Systems with Turn‐On Luminescence
Author(s) -
Josse Pierre,
Allain Magali,
Calupitan Jan Patrick,
Jiang Yue,
Cabanetos Clément,
Roncali Jean
Publication year - 2020
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202000420
Subject(s) - intermolecular force , materials science , amorphous solid , acceptor , luminescence , molecular dynamics , photoluminescence , molecule , intramolecular force , chemical physics , side chain , thin film , conjugated system , crystallography , polymer , photochemistry , nanotechnology , optoelectronics , stereochemistry , computational chemistry , chemistry , organic chemistry , composite material , physics , condensed matter physics
A series of simple donor–acceptor molecules consisting of an oligo‐oxyethylene (OOE) N ‐substituted diphenylamine connected to a dicyanovinyl (DCV) acceptor group by a thienyl π‐conjugating spacer are synthesized. Amorphous deep‐red freshly cast thin films rapidly evolve towards an almost colorless pale beige poly‐crystalline stable material from which a deep‐red photoluminescent state can be switched‐on by mechanical stimulation. The effects of the length of the OOE chain on the molecular packing of the material and on the dynamics of the recovery process and aggregation in solution are analyzed. Crystallographic results show that the length of the OOE chain directly controls the molecular packing from head‐to‐tail arrangement of the dipoles for short chain to co‐facial dimers leading to a non‐centrosymmetric material with nonlinear optics (NLO) activity for the longer ones. The analysis of the dynamics of the self‐recovery process of thin films and of molecular aggregation in solution shows that the dynamics of both processes is directly controlled by the length of the OOE chain. Since, as confirmed by optical and electrochemical results, the OOE substituents have strictly no influence on the electronic properties of the π‐conjugated system, the observed effects are unambiguously related to changes in intermolecular interactions.