# Synthetic Routes to Silsesquioxane-Based Systems as Photoactive Materials and Their Precursors
## 1 Introduction
also presented a synthesis of asymmetric pyrylene-based diimine with thePOSS unit as pendant moiety and \(N\)-isopropylacrylamide unit that was subjected to atom transfer radical polymerization (ATRP), resulting in a well-defined amphiphilic fluorescent polymer with a 58% yield [29]. Their fluorescence red emission bands were retained at ca. 645 nm (\(\lambda_{\text{ex}}=495\) nm) and were found to be temperature-dependent (intensity enhanced with an increase in temperature). This could be used to fabricate thermo-responsive materials, in biosensors, and so on. The imitation reaction was used by [PERSON] et al. to anchor rhodamine B hydrazide units using propyloxy-p-benzaldehyde-functionalized T\({}_{10}\) silsesquioxane (Figure 4) [33]. The precursor reagent T\({}_{10}\) was obtained via nucleophilic substitution cage rearrangement of octa(chloropropyl)silsesquioxane, but reported reaction conditions that resulted in a 15% yield of T\({}_{10}\). Here, the authors reported on the synthesis of penta-substituted rhodamine B hydrazide T\({}_{10}\) derivative with very high (98%) yield. The bulkiness of rhodamine B hydrazide moieties enabled the introduction of only five units onto the Si-O-Si core. Nevertheless, the photophysical properties of this compound were found to be interesting in the presence of Hg\({}^{2+}\) ion, with absorption at \(\lambda_{\text{ab}}=520\) nm and red emission (\(\lambda_{\text{ex}}=520\) nm) that increased with the ion concentration rise. The observed active  
Figure 3: Reaction route for the synthesis of asymmetric pyrylene diimide. form that exhibited fluorescence was a spiro-lactam form of rhodamine B unit after Hg\({}^{2+}\) chelation. Analogous tests were performed for others metal ions but none of them gave the same fluorescence response. This was a very interesting work enabling use of the presented compound as a selective dual chemosensor for Hg\({}^{2+}\) that afforded both fluorescence enhancement and color change from colorless to pink, with a 0.63 ppb detection limit. As reported by [PERSON], [PERSON] and co-workers [34], an example of the parallel amidation and esterification of 4-(1,2,2-triphenylvinyl)benzoic acid used for the modification of octa(aminopropyl)POSS and octa [hydroxypropylodi(methyl)siloxy]POSS, respectively, resulted in the formation of analogous octafunctionalized silsesquioxanes differing from each other with the spacer (containing amide or ester functionality) between POSS and organic areen coronae. These two systems were obtained with 77% and 58% yields. Although these two compounds exhibited absorption spectra (in THF) at around \(\lambda_{\text{ab}}\) = 325 nm, the effective emission band was presented only for the amide derivative (a wide of spectrum ranging from 375 to 600 nm) with a maximum \(\lambda_{\text{em}}\) = 458 nm (\(\lambda_{\text{em}}\) = 365 nm). This compound was found to be a selective chemosensor for Cu\({}^{2+}\) ions (other TMs were also tested) by fluorescence quenching in DMSO. Anchoring the POSS unit on 3,4-ethylenedioxythiophenes was explored by [PERSON] and [PERSON] et al. [35; 36; 37]. They proposed an amidation reaction of amonipropyl(heptaisobutyl)POSS with anhydride, followed by a palladium-mediated Stille reaction to obtain the respective reagents, with moderate (44%-59%) yields. These systems were reagents in the electrochemical (co-)polymerization, resulting in highly conjugated poly(3,4-ethylenedioxythiophenes) (PEDOTs) known for their interesting electrochemical properties. PEDOTs can be used as elements in electrochromic device fabrication because their color depends on the oxidation state. [PERSON] and [PERSON] [38; 39] reported the use of mono(3-mercaptoethanolpropyl) heptaisobutylocasislessquioxane as a dopant in the formation of solid stable perovskite (CsPbX\({}_{3}\) (X = Br or I)) colloidal nanocrystals (NCs), with a surface protection of POSS as luminophores exhibiting different emissions colors.