Mirror-Symmetry-Breaking in Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-biphenyl] (PF8P2) is Susceptible to Terpene Chirality, Achiral Solvents, and Mechanical Stirring

Abstract

Solvent chirality transfer of (S)-/(R)-limonenes allows the instant generation of optically active PF8P2 aggregates with distinct circular dichroism (CD)/circularly polarized luminescence (CPL) amplitudes with a high quantum yield of 16-20%. The present paper also reports subtle mirror-symmetry-breaking effects in CD-/CPL-amplitude and sign, CD/UV-vis spectral wavelengths, and photodynamics of the aggregates, though the reasons for the anomaly are unsolved. However, these photophysical properties depend on (i) the chemical natures of chiral and achiral molecules when used in solvent quantity, (ii) clockwise and counterclockwise stirring operations, and (iii) the order of addition of limonene and methanol to the chloroform solution.

Tempo-spatial chirogenesis. Limonene-induced mirror symmetry breaking of Si Si bond polymers during aggregation in chiral fluidic media

“…By adding poor solvent (methanol) to the nBuPS solution, CD-and CPL-active nBuPS is instantly formed during aggregation. This terpene chirality induced aggregation process was already established in our previous papers [44,[49][50][51][52][53][54], however nBuPS and related diarylpolysilanes were not studied.…”

“…This open system allows investigation of tempo-spatial molecular chirality transcription of the soft aggregates. Particularly, time-dependent alteration in the size of optically active aggregates becomes measurable because optically active aggregation becomes popular in recent years [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Aiming at realizing the soft matter coacervate system enabling open flows of chiral substances in the ground state and/or circularly polarized radiation in the photoexcited state, the following five bis(p-alkylphenyl)polysilanes, were chosen: nBuPS, EtPS, iPrPS, iBuPS, and tBuPS ( Fig.…”

“…The other four EtPS, iPrPS, iBuPS, and tBuPS possibly adopt a similar stiff backbone because they commonly have bulky diaryl groups attached to the backbone. Non-polar (S)-/(R)-limonene and (1S)-/(1R)-α-pinene were chosen as chiral terpenes because limonene and α-pinene are efficient stereogenic center transferable solvents for several circular dichroism (CD)-silent and/or circularly polarized light (CPL)-silent πand σ-conjugated polymers [44,[49][50][51][52][53][54]. CD-active and/or CPL-active aggregation of these polymers occurs with the help of van der Waals force only with these terpenes.…”

Supramolecular Chirality: Solvent Chirality Transfer in Molecular Chemistry and Polymer Chemistry

“…However, nonpolar (S)-and (R)-α-pinenes are inducible to CD-and CPL-active polymers [126]. We assume that, similar to the non-coplanar ability of biphenyl, due to H-H repulsion (Figure 22), the inherent twisting ability between the nearest neighboring fluorene rings and between fluorene and the adjacent vinylene moiety is responsible for the double-well potential, leading to the instability of coplanar fluorene ring conformations ( Figure 23) [125][126][127][128]130,131]. Indeed, fluorenes linked with a C≡C triple bond did not produce any CD-active aggregate, due to the lack of H-H repulsion (Figure 23) [128].…”

Achiral Polydialkylsilane Aggregates That Record Stirring Direction

“…[10] However,w hen molecules or aggregates are large enough to decreaset he local effects of the Brownian motion of the solvent molecules, they might be sensitive to fluidic flows. In polymer systems, both the alignment of DNA [11] and the aggregate of as emi-rigid polymer [12] have been found to be sensitive to fluidic flows.…”