# Synthetic Routes to Silsesquioxane-Based Systems as Photoactive Materials and Their Precursors
## 1 Introduction
### Cross-Metathesis and Related Modifications for Silyalkenyl Fragment Formations
On the other hand, the phosphorescence of metal complexes, especially iridium or platinum, and their use in specific types of OLED devices was reported [110]. However, these complexes may suffer from self-quenching in the solid due to interaction aggregation. This may be improved by anchoring them onto the Si-O-Si core (described in Section 3.4). The idea of grafting of non-conjugated polymers (as a transparent matrix) with the metal complex covalently attached to the polymer backbone was studied. In this scenario, solubility would be additionally improved in comparison to the conjugated counterparts, thus facilitating application. An interesting paper of [PERSON] and [PERSON] et al. reported on the efficient synthesis of poly(methylmethacrylate) via the AIBN (2,2'-Azobis(2-methylpropionitrile))-mediated radical copolymerization of two types of methylmethacrylates (bearing mono(propyl)heptaphenyl(silsesquioxne) = M3, carbazole unit = M1, with styryl-based iridium complex = M2) used in different molar ratio (POSS from 2 to 8 mol %) and resulting in copolymeric systems (Figure 40) [126]. Depending on the specific ratio of comonomers, the molecular weights varied (\(M_{n}\) = 5100-19,400 g/mol, suggesting formation of other oligomeric systems), with PDI from 1.4 to 2.2. The obtained materials were characterized in terms of their absorption emission properties, comparing the results with analyses for each monomer M2, M3 along with the copolymer without  
Figure 17:6 The synthetic route of the copolymer-based Ir complex. Figure 17:7 Reaction path towards octa-functionalized silsesquioxane with rhodamine 6G. POSS (i.e., M2 + M3 and final ternary copolymers M1 + M2 + M3 with 2-8 mol % POSS contribution). The absorption spectra of copolymers in DCM showed peaks at \(\lambda_{\rm{ab}}\) = 237, 261, 294, 328 and 342 nm, which came from the carbazole segment and iridium complex moiety. The photoluminescence spectra (\(\lambda_{\rm{ex}}\) = 365 nm) in solution exhibited blue and green emission bands \(\lambda_{\rm{em}}\) ca. 420 and 435 nm (derived from the host carbazole unit M1), with additional green emission bands at \(\lambda_{\rm{em}}\) ca. 530 nm (derived from the guest iridium complex fragment M2). The band at 530 nm was enhanced with the increase of iridium complex content from 0.5 to 5.0 mol % while the bands around 420 and 435 nm decreased in intensity. There was energy transference suggested by the host (donor) carbazole moiety to the guest (acceptor) iridium complex moiety, which is also dependent on the content of Ir units along with the POSS moiety. However, the ternary copolymer with 5 mol % or iridium units and 2 mol % of POSS exhibited a significant enhancement of the green emission that may have indicated the separation of Ir complex units, preventing their aggregation, so that the concentration-quenching was restrained in the solution. In a solid state, the emission spectra presented only one little red-shifted green emission band (up to \(\sim\)10 nm) but there was an interesting enhancement of the spectra intensity for the copolymer with 0.5 mol % of Ir complex content, meaning that the POSS unit prevented the aggregation of Ir units more effectively--a phenomenon that was more intensive with an increase in POSS content. The quantum efficiencies for these systems in a solid state were also higher, up to 52% (when compared to binary copolymers M2 + M3, \(\Phi\) = 7-24%), which suggests that incorporation of POSS units enhances luminescence profoundly. Thermal resistance was also improved. These aspects make the obtained materials definite candidates for OLED devices.