# Synthetic Routes to Silsesquioxane-Based Systems as Photoactive Materials and Their Precursors
## 1 Introduction
### Cross-Metathesis and Related Modifications for Silyalkenyl Fragment Formations
As a result, the emission spectra of W\({}_{62}\) and W\({}_{53}\) possessing two (W\({}_{62}\)) and three (W\({}_{53}\)) Y groups also exhibited the THF/water mixture emission dependence. The emission spectrum of W\({}_{62}\) in THF presented two peaks at \(\lambda_{\rm em}\) = 410 and 440 nm, but with the increasing content of water an enhancement of two new red-shifted peaks at \(\sim\)530 and 570 nm were noted. As a result, the light band was fully covered from 400 to 700 nm, making the realization of a white light emission possible. Interestingly, this feature was preserved in the solid state and enabled its application as dopants in the synthesis of white-light-emitting materials. [PERSON], [PERSON] and [PERSON] et al. presented T\({}_{8}\) silsesquioxane-based dyes that were obtained by a copper(l)-catalyzed 1,3-dipolar cyclo-addition of octakis(3-azidopropyl)ocatasilsesquioxane with alkyne-substituted 4,4-di-fluoro-4-bora-3a,4a-diaza- s-indacene (BDP) chromophore (Figure 38) [124]. The reaction conditions (also reagent stoichiometry) as well as the type of Cu catalyst affected the number of BDP substituents attached to the T\({}_{8}\) core, and the process was carried out to obtain mono-BDP-substituted and fully (i.e., octa-BDP) substituted product. These two systems, along with their respective BDP analogues (as model compounds), were analyzed in terms of their photophysical properties. P1 and P8 exhibited similar absorption and fluorescence properties (P1: \(\lambda_{\rm ab}\) = 526 nm, \(\lambda_{\rm em}\) = 540 nm; P8: \(\lambda_{\rm ab}\) = 523 nm, \(\lambda_{\rm em}\) = 546 nm) but P8 revealed substantial fluorescence decay that was attributed to the strong \(\pi\)-\(\pi\) interaction of BDP units and formation of H-type or \"sandwich\" aggregates. Additionally, the fluorescence of P8 was strongly dependent on the type of solvent used (its poor solubility in non-polar media), and acetone was found to be the best. The compounds were analyzed for their lasing properties (in solution and in a solid state) in comparison to the BDP molecular analogues. Interestingly, compound P1 reached a laser efficiency of up to 56% (in the solid matrix) and up to 60% (in ethyl acetate solution) while maintaining a high photostability when compared to the  
Figure 17:3 Reaction path towards octa- and mono-BDP derivatives of T\({}_{8}\) silsesquioxane (BDP–POSS). Figure 17:4 Synthetic route to octa(azidomethylene)spherosilicate derivatives obtained by a 1,3-dipolar Huisgen reaction. parent BDP model (35%). This proves the high application potential of BDP-POSS-based systems in the formation of new photonic materials as alternative sources for optoelectronic devices. An interesting work on the radical thiol-ene reaction (TEC) (mediated via DMPA = 2,2-Dimethoxy-2-phenylacetophenone) of propargyl thiol and octa(vinyl)POSS (OVS) functionalization, and its further ligation with rhodamine 6G, was presented by [PERSON] et al. (Figure 17:5) [125]. The authors reported on the photophysics of compound and related absorption (\(\lambda_{\text{ab}}\) = 532 nm)--emission spectra (\(\lambda_{\text{em}}\) = 554 nm) that were pH dependent and increased in intensity with a decrease in pH value. Due to their problems with solubility, an increase of intensity was noted for higher-content ethanol in the water/ethanol solution. This compound was tested as a fluorescent chemosensor for a variety of metals, and the results indicated a positive response for Au\({}^{3+}\) ion (50:50 water/ethanol, pH = 1 and molar concentration of rhodamine units of 10\({}^{-5}\) M). Under these conditions, there was a strong fluorescence emission enhancement. As a result, POSS-Rh8 may be used as selective fluorescent chemosensor for the selective determination of Au(3+) ions in aqueous media. One of the reactions applied in the chemistry of silsesquioxanes was free radical copolymerization leading to hybrid materials that are more amenable to solution techniques (e.g., spin-coating that results in large-area device fabrication).