# Synthetic Routes to Silsesquioxane-Based Systems as Photoactive Materials and Their Precursors
## 1 Introduction
### Cross-Metathesis and Related Modifications for Silyalkenyl Fragment Formations
It was demonstrated that the products (H1-4) and their free emitter counterparts showed nearly the same \(\lambda_{\rm ab}\) and broader absorption bands for the hybrids (H), that may have originated from the \(\sigma\)-\(\pi\) conjugation effect of Si-C=C- in obtained materials. The authors proved that the combination of an inorganic POSS core with stilbene chromophores endowed the resulting materials with novel optical limiting properties and high thermal stability. However, there wano information on how the presence of \(\alpha\) and \(\beta\) isomers in H affected these properties. In 2016, [PERSON] et al. developed a new spherosilicate-based compound containing carbazole and pyrene units [103]. This new organic-inorganic amorphous hybrid material was obtained in a two-step reaction involving: (1) synthesis of chromophore using alkylation of \(N\)-dipyrenylcarbazole with allyl bromide, and (2) hydrosilylation of obtained olefin with Q\({}_{8}\)M\({}_{8}\) in the presence of [PERSON]'s catalyst (Figure 30). Figure 15:4 Functionalization of octahydrospherosilicate with \(N\)-allyl-carbazole derivative. Figure 15:5 Synthetic pathway for the hydrosilylation of terminal alkynes with OHS. The authors demonstrated that this newly-developed POSS derivative exhibits excellent thermal stability, efficient control of POSS dispersion behavior and good film-forming properties. The photophysical properties of the product were determined and compared with chromophore used in solution (CHCl3) and in solid state. The UV-vis spectra of both compounds showed a strong absorption band at \(\lambda_{\text{ab}}=281\) nm, which can be attributed to the \(\pi\)-\(\pi^{\star}\) local electron transition of the carbazole fragment, and a longer-wavelength absorption band at \(\lambda_{\text{ab}}\) ca. 349 nm, which corresponds to the \(\pi\)-\(\pi^{\star}\) electronic transition of the chromophore backbones. The shape and position of the PL emission spectra was different for the product and chromophore, which can be attributed to the fact that bulky POSS cages reduce the extent of substrate aggregation. This conclusion also supports measurement of PL quantum efficiency (PLQE) of the product (90%), which was much higher than that of the separate chromophore (66%). The results of emission in solid state were interesting, and showed ca. 20 nm red-shift in \(\lambda_{\text{em}}\) compared to the solution-phase spectra. This suggests the presence of weak van der Waals forces and intermolecular \(\pi\)-\(\pi\) interactions of adjacent chromophore fragments. Although significantly red-shifted behavior was observed in the film state, the final product exhibited an emission band centered at 454 nm, which was substantially blue-shifted compared to that of the substrate film (463 nm). These observations indicate that the POSS cage inhibits the aggregation of chromophore units to improve their color purity and stability both in solution and the solid state. This also promotes its possible applications in solution-processed optoelectronic devices. [PERSON] and [PERSON] et al. reported on the synthesis of two organic-inorganic nanohybrid materials obtained by decorating spherosilicate POSS cores with 2,3,4,5-tetraphenylsilole units through a one-step hydrosilylation process (Figure 31) [104]. As presented in Figure 31, Q8M8 and Q8V8 were used as synthetic scaffolds and two different silole derivatives were chosen as their reagents. Expected products (**1**, **2**) were isolated with 57% and 47% yields, respectively. Their thermal and photophysical properties were determined along with their utility as potential sensors for the selective detection of nitroaromatic explosives in aqueous media. As expected, thermal stability of these systems was improved (up to 390 \({}^{\circ}\)C). Photophysical properties of both products were solvent-dependent. It was observed that product **1** emits weakly at 486 nm in THF and at 496 nm in a mixture of THF/water (1:9), while in 90% water content the photoluminescence intensity is 68-fold higher than in pure THF.