Aromatic oligoamide foldamers as versatile scaffolds for induced circularly polarized luminescence at adjustable wavelengths

Abstract

et al.. Aromatic oligoamide foldamers as versatile scaffolds for induced circularly polarized luminescence at adjustable

Influence of Positional Isomerism on the Chiroptical Properties of Functional Aromatic Oligoamide Foldamers

“…max.~4 50-470 nm). [11] However, the present study reveals an increased fluorescence quantum yield with elongation of the helix from 4 to 6 monomers: Φ lum = 0.058 vs. 0.014 for Q 6 and Q 4, respectively. This blue shift and increased emission quantum yield is consistent with an enhanced rigidification of the scaffold and hence less effective non-radiative deactivation pathways.…”

“…[20] Monomers based on an 8-amino-2-quinolinecarboxylic acid backbone and functionalized at position 4 were employed. [11,15] The quinoline monomer bearing the bis(9,9-dimethyl-9H-fluoren-2-yl)amine (DFA) substituent is hereafter named Q DFA while the quinoline analogue equipped with 1-ethynyl-3,5-bis (trifluoro-methyl)benzene is named Q CF3 . In order to evaluate the effect of the number of functional groups and their position on the helical scaffold, while preventing mutual steric interactions, positions 2 and 6 of the hexameric sequence were preferred for functionalization.…”

“…The reference hexamer Q 6 exhibits strong Cotton effects in the 230-430 nm spectral range, which is a characteristic feature of chromophoric quinoline oligoamide helices. [11,15,16,22] In anal- Figure 4. ECD spectra of the quinoline hexamers: P-Q 6 (black, solid line), M-Q 6 (black, dotted line), P-Q 6 DFA (2) (red, solid line), M-Q 6 DFA (2) (red, dotted line), P-Q 6 DFA (6) (orange, solid line), M-Q 6 DFA (6) (orange, dotted line), P-Q 6 DFA (2,6) (blue, solid line), M-Q 6 DFA (2,6) (blue, dotted line), P-Q 6 DFA (2) CF 3 (6) (green, solid line), M-Q 6 DFA (2) CF 3 (6) (green, dotted line), P-Q 6 CF 3…”

“…[10] In this context we have recently exploited aromatic oligoamide foldamers as a new platform for CPL modulation. [11] Aromatic oligoamide foldamers are synthetic oligomers that are able to adopt highly stable and predictable folded conformations in solution due to intramolecular interactions between adjacent units (e. g. hydrogen bonds, electrostatic repulsions and aromatic stacking). [12] Moreover, the sequential nature of these oligomers allows synthetic flexibility and high modularity for precise positioning of functional groups at predetermined location(s) on the helical scaffold.…”

Hyper-Rayleigh Scattering as a New Chiroptical Method: Uncovering the Nonlinear Optical Activity of Aromatic Oligoamide Foldamers

“…Moreover, aromatic oligoamides allow photoinduced charge transfer processes over long distances via multidimensional charge transport mechanisms [40][41][42] and can also behave as strong CPL emitters. 43,44 Here, we report the rational design and preparation of molecular helices based on a quinoline oligoamide backbone functionalized by electronically active substituents, along with the assessment of their NLO properties in solution. In particular, HRS studies were performed using either linearly-polarized (LP) incident light ( Figure 1A) or circularly-polarized (CP) incident light ( Figure 1B) to probe the enantiomeric differential scattering intensities and quantify, for the first time, the hyper-Rayleigh optical activity (HROA) of such chiral molecular systems.…”