Synthesis and Steady State Photophysical Property Analysis of Beads on a Chain (BoC) Silsesquioxane Oligomers Containing Arene and Heteroarene Cross-linkers

Beads on a Chain Fluorescent Oligomeric Materials: Interactions of Conjugated Organic Cross-Linkers with Silsesquioxane Cages

“…This suggests that our increased PLQY results from global energy transfer within the combined phenyl SQ and PQ system to the central acceptor linker as a sink, which can then release energy through fluorescence. We have found that shorter oligomers tend to be brighter as well . Note that in the PQ oligomer the 320 nm absorption band (Figure B) present in the other oligomer systems is missing likely due to the electronic withdrawing nature of the linker improving interactions with donor phenyls, as discussed in the transient absorption data.…”

“…This is in comparison to BoC oligomers with divinylbenzene linkers, which showed large emission red-shifts in the oligomers. ,, This suggests that only slight interactions are taking place between the phenyl cages and the linkers here. This could be due to the higher proportion of T 10 cage sizes in this system, which show less ability to form excimers, or due to the spatial overlap between the linkers and cage phenyl systems, both of which have been observed to result in spectral red-shifts in the oligomeric compounds over models. Further analysis is undertaken to understand the small changes in spectra using time-resolved fluorescence and femtosecond transient absorption measurements.…”

“…The synthesis of mixed vinyl/phenylSQs was performed based on our previous report . In addition to those methods, the separation of vinyl/phenylSQs to increase the proportion of di- and trivinyl was undertaken as outlined below.…”

“…However, few researchers have looked at gaining a better understanding of the photophysical and/or electronic properties of silsesquioxanes with bridging conjugated organic groups, with the majority focus being toward application driven light emitting or photoresponsive network materials. ,− Less study has been devoted to linked soluble (lightly branched) SQs (BoC), which we expand on in this work. − Asuncion and Laine developed the earliest examples of BoC systems having unique photophysical properties. They used fluoride catalysis to rearrange cages into mixed functionalities with bromostyrenyl/phenyl units as one component and vinyl/phenyl units as a second component to form mixed T 10 /T 12 cages, which were coupled using Heck cross-coupling reactions to form 1,4-divinylbenzene conjugated organic bridges .…”