Supramolecular Polymerization of [5]Helicenes. Consequences of Self-Assembly on Configurational Stability

Abstract

The supramolecular polymerization of [5]helicenes 1 and 2 is investigated. The self-assembly of these helicenes proceeds by the operation of H-bonding interactions with a negligible participation of π-stacking. The enantiopurity of the sample has a dramatic effect on the supramolecular polymerization mechanism since it reverts the isodesmic mechanism for the racemic mixture to a cooperative one for the enantioenriched sample. Noticeably, the formation of supramolecular polymers efficiently increases the configurational stability of 1,14-unsubstituted [5]helicenes.

Symmetry-based rational design for boosting chiroptical responses

“…State-of-the-art calculations further revealed the decisive role of molecular symmetry (which determines the electric and magnetic transition Table 4). This theory-driven protocol for predicting the ground-state and excited-state chiroptical properties is not restricted to the design of superior chiroptical molecules but is expandable to the design of two-dimensionally and three-dimensionally aligned chiral elements, such as chiral supramolecular assembly 22 and chiral surface organization 23 .…”

Hierarchy of Asymmetry in Chiral Supramolecular Polymers: Toward Functional, Helical Supramolecular Structures

“…However, performing the same experiment, but with MCH as a solvent, results in negligible changes to the CD spectra upon heating the sample at the same temperatures as those utilized with CHCl 3 . These results confirm that supramolecular polymerization contributes to the efficient stabilization of [5]helicenes without incorporating any substituent at the fjord region …”

“…These resultsc onfirm that supramolecular polymerization contributest ot he efficient stabilizationo f [ 5]helicenes without incorporating any substituent at the fjord region. [54]…”

Supramolecular polymerization of chiral molecules devoid of chiral centers

“…73 In 2018 the group of Luis Sánchez reported the supramolecular polymerization of 5,7,8,10-tetrasubstituted [5]helicene derivatives with amide hydrogen bonding units on the 5-and 10-positions. 74 Two molecules were synthesized: one with a single amide hydrogen bonding unit at each position and a long alkyl solubilizing group (6) and one with two amide hydrogen bonding units at each position separated by a short alkyl linker (7). Compound 7 did not form SPs in solutions of methylcyclohexane (MCH), whereas compound 7 was shown to form SPs in solutions of MCH through amide hydrogen bonding (Fig.…”

“…AFM phase image (c) of the columnar aggregates formed from M-7 (10 μmol L -1 , 298 K, mica as surface). Reproduced with permission from Valera et al74…”