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Influence of the Z / E Isomerism on the Pathway Complexity of a Squaramide‐Based Macrocycle
Author(s) -
Orvay Francisca,
Cerdá Jesús,
Rotger Carmen,
Ortí Enrique,
Aragó Juan,
Costa Antonio,
Soberats Bartolome
Publication year - 2021
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.202006133
Subject(s) - supramolecular chemistry , squaramide , chemistry , polymerization , crystallography , monomer , hydrogen bond , supramolecular assembly , cucurbituril , stereochemistry , crystal structure , molecule , polymer , organic chemistry , enantioselective synthesis , organocatalysis , catalysis
The rising interest on pathway complexity in supramolecular polymerization has prompted the finding of novel monomer designs able to stabilize kinetically trapped species and generate supramolecular polymorphs. In the present work, the exploitation of the Z/E (geometrical) isomerism of squaramide (SQ) units to produce various self‐assembled isoforms and complex supramolecular polymerization pathways in methylcyclohexane/CHCl 3 mixtures is reported for the first time. This is achieved by using a new bissquaramidic macrocycle ( MSq ) that self‐assembles into two markedly different thermodynamic aggregates, AggA (discrete cyclic structures) and AggB (fibrillar structures), depending on the solvent composition and concentration. Remarkably, UV–vis, 1 H NMR, and FT‐IR experiments together with quantum‐chemical calculations indicate that these two distinct aggregates are formed via two different hydrogen bonding patterns (side‐to‐side in AggA and head‐to‐tail in AggB ) due to different conformations in the SQ units ( Z,E in AggA and Z,Z in AggB ). The ability of MSq to supramolecularly polymerize into two distinct aggregates is utilized to induce the kinetic‐to‐thermodynamic transformation from AggA to AggB , which occurs via an on‐pathway mechanism. It is believed that this system provides new insights for the design of potential supramolecular polymorphic materials by using squaramide units.