# Synthetic Routes to Silsesquioxane-Based Systems as Photoactive Materials and Their Precursors
## 1 Introduction
### Cross-Metathesis and Related Modifications for Silyalkenyl Fragment Formations
Interestingly, the cross-metathesis for OVS proceeded with 0.5 mol % of the catalyst and at room temperature only in the cases of T\({}_{10}\) and T\({}_{12}\) at 40 \({}^{\circ}\)C. The purification of these compounds concerned filtration over Celite, precipitation and column chromatography, obtaining final products with 74%-82%yields. Additionally, the p-NH\({}_{2}\)-vinylStilbene product was transformed into respective benzamide derivatives. All of the compounds were characterized in terms of photophysical properties. For T\({}_{8}\) compounds, the absorption (\(\lambda_{\mathrm{ab}}\) 260-358 nm) and emission (\(\lambda_{\mathrm{em}}\) 304-482 nm) spectra showed red shifts in comparison with their organic counterparts (styrene and p-vinylstilbene). The octa(XStyryl)silsesquioxane T\({}_{8}\) showed smaller red-shifts than octa(R'Stilbenevinyl) silsesquioxane T\({}_{8}\)compounds (10-40 nm shifts vs. 30-80 nm shifts--i.e., Stokes shifts at ca. 50 nm) as might be expected due to a larger conjugation for the R\({}^{\prime}\)StilbenevinylT\({}_{8}\) compounds. The red shift is also larger in the presence of more electron-donating groups (-OMe). The NH\({}_{2}\)StilbeneVinylT\({}_{8}\) exhibited effects of solvent polarity on its emission behavior (DCM and MeCN) due to charge-transfer (CT) interactions that were also proved by DFT calculations, as noted previously [58]. The StilbeneVinylT\({}_{10}\) and T\({}_{12}\) derivatives were separated effectively due to the proper solvent choice. Their photophysical properties were compared along with the StilbeneVinylT\({}_{8}\) to observe the impact of the cage size and  
Figure 17: Synthetic reaction route based on sequential cross-metathesis and Sonogashira coupling for dumbbell-shaped \(\pi\)-conjugated systems with POSS as pendant groups. symmetry measured in solution (THF) and films. In general, the red-shift emission was observed for all three compounds, due to the \(\pi\)-conjugation, and the additional red-shifted spectra for films revealed the aggregation of chromophores, as expected. Additionally, two-photon spectroscopy analysis was performed to compare the polarization and non-linear absorption properties of the separated T\({}_{8}\), T\({}_{10}\) and T\({}_{12}\) cages along with the p-triethoxysilylvinylstilbene and p-vinylstilbene. Due to the differences in symmetry, especially between T\({}_{10}\) and T\({}_{12}\) cages, these compounds displayed changes in the dipole moment of excitation and exhibited different emission maxima wavelengths, with excitation at \(\lambda_{\text{ex}}\) = 333 nm (T\({}_{10}-\lambda_{\text{em}}\) = 386 nm, high intensity), \(\lambda_{\text{ex}}\) = 400 nm (T\({}_{10}-\lambda_{\text{em}}\) = 453 nm) and \(\lambda_{\text{ex}}\) = 800 nm (T\({}_{10}\) - \(\lambda_{\text{em}}\) = 450 nm, the highest intensity when compared with T\({}_{8}\) and T\({}_{12}\)). Indeed, the observed impact on fluorescence decreased for bigger T\({}_{12}\) cages, which may have been derived from the cage symmetry and/or the chromophores' proximity. Moreover, a red-edge effect in these 3D molecular structures was observed (i.e., the red-shifted emission wavelengths upon shifting of the excitation wavelength to the red end of the abs. spectra. The highest effect was observed in the case of deca(Stilbene)silesquisoxane T\({}_{10}\), which suggests a possible application of these compounds as a new class of hybrid materials offering switchable emissions. The cross-metathesis process, leading to polymeric POSS systems (e.g., ADMET reaction), was described in Section 3.1 due to the ease of comparison of the products, and is analogous in structure to a Heck coupling reaction [63]. The [PERSON] research group presented an interesting combination of analogous cross-metathesis and Heck coupling sequences leading to octa(carborane-Stilbenevinyl)silesquisoxane T\({}_{8}\) cages (Figure 19) [78]. The cross-metathesis of OVS with p-bromostyrene was perfumed using the synthetic procedure reported by [PERSON] [71].