Time-evolved, far-red, circularly polarised luminescent polymer aggregates endowed with sacrificial helical Si-Si bond polymersElectronic supplementary information (ESI) available: Experimental section, CPL/PL/CD/UV-Vis spectra, DFT/TD-DFT-calculations, photographs of the colour change and characterisation of F8DBT by 1H-NMR. See DOI: 10.1039/c7qm00096k

An enantiomeric pair of non-charged, helical dialkylpolysilanes ( PSi- R and PSi- S ) were endowed with circularly polarised luminescence (CPL) at 700 nm and circular dichroism (CD) at 660 nm when non-helical poly{[dioctylfluorene]- alt -[bis(thiophenyl)-benzothiazole]} ( PF8DBT ) formed a hetero-aggregate with PSi- R and PSi- S in a 1-to-1 ratio as repeating units. The initial ultraweak CPL ( g em ) and CD ( g abs ) amplitudes of the as-prepared aggregates were magnified up to −0.019 at 706 nm (induced by PSi- S ) and +0.017 at 695 nm (induced by PSi- R ) after prolonged ageing at ambient temperature for 24 h. These CPL amplitudes were maintained after the selective photoscissoring of PSi- S and PSi- R at 313 nm for 60 s. A time-dependent growth behaviour in the hetero-aggregate size (initially 400 nm; reached 2000 nm in one day) was observed and characterised using dynamic light scattering (DLS). To investigate the origin of the time-evolution characteristics, the energy potential, dipole moments and CD/UV-Vis-near-infrared (NIR) spectra were simulated upon altering the dihedral angle sets of several model oligomers of PF8DBT using density functional theory (DFT)/time-dependent DFT (TD-DFT) (B3LYP/6-31G(d,p)). An additional Zerner's Intermediate Neglect of Differential Overlap (ZINDO) calculation qualitatively established that the two hypothetical, chirally dipole-dipole-cancelled, π - π - stacked, slipped dimers cause red shifts in the CD and UV-Vis-NIR spectra, which were associated with an enhanced | g abs |, 1 × 10 −3 at 715 nm and 0.5 × 10 −3 at 660 nm, compared to the corresponding monomeric value (| g abs | 0.1 × 10 −3 at 620 nm) obtained using TD-DFT. Non-charged helical polysilanes ( PSi ) were spontaneously endowed with CPL on the order of g em = ±0.02 at 700 nm when non-helical red- and far-red π-conjugated polymeric ( PF8DBT ) aggregates were employed after ageing at 20-25 °C for 24 h, followed by PSi -selective photoscissoring at 313 nm for 60 s.