H-bonding driven J-type aggregation and cooperative supramolecular polymerization of a sulfur-substituted chiral naphthalene-diimide (NDI)-derivative (S,S)-NDI-2 in decane leads to remarkable enhancement of fluorescence quantum yield (43.3 % from 0.5 % in the monomeric state) and intense CPL signal in the aggregated state with a high luminescence dissymmetry factor (glum ) of 4.6×10-2 . A mixture of NDI-2 with a structurally similar NDI-derivative NDI-1 (mixture of racemic (S,S)- and (R,R)- isomers and the achiral derivative) in 1:9 (NDI-2/NDI-1) ratio, when heated and slowly cooled to room temperature, showed no enhanced CD band, indicating lack of any preferential helicity. However, when a monomeric solution of the NDI-1 in tetrahydrofuran (THF) was injected to preformed seed of NDI-2 in decane, a prominent CD signal appeared, indicating chiral amplification resulting in induced CPL with high glum value of 2.0×10-2 from mostly (>98.5 %) diastereomeric mixture.
Keywords: aggregation; chiral resolution; chirality; circular dichroism; hydrogen bonds; supramolecular polymerization.
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