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Hydrogen‐Bonded Dimeric Capsules with Appended Spiropyran Units: Towards Controlled Cargo Release
Author(s) -
Ferreira Pedro,
Moncelsi Giulia,
Aragay Gemma,
Ballester Pablo
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.202101643
Subject(s) - spiropyran , merocyanine , isomerization , chemistry , protonation , pyrrole , monomer , photochemistry , proton nmr , tetra , molar concentration , triflic acid , polymer chemistry , medicinal chemistry , stereochemistry , photochromism , organic chemistry , catalysis , ion , polymer
We report the synthesis of unprecedented tetra‐urea derivatives of calix[4]arene and calix[4]pyrrole containing four spiropyran (SP) units at their upper rim. We investigate the photo‐ and acid‐induced isomerization of the monomeric and homo‐dimeric tetra‐ureas derivatives using UV‐Vis and 1 H NMR spectroscopies. At micromolar concentration, irradiation of the samples with 365 nm light induces changes in their absorption spectra that are consistent with SP→merocyanine (MC) isomerization. However, analogous experiments at millimolar concentration do not produce noticeable changes in the 1 H NMR spectra. The addition of triflic acid to micromolar and millimolar solutions of the tetra‐ureas produces the quantitative isomerization of the SP units to the protonated merocyanine form (E‐MCH + ) and the simultaneous disassembly of the capsular dimers to form ill‐defined aggregates. The neutralization of the acid solutions resets the SP form. Under these acid/base treatment conditions, the controlled release of the included guest and the reassembly of the all‐SP tetra‐urea dimers occurs at different extents depending on its calix[4]arene or calix[4]pyrrole scaffold.