## 3 Results
### Characterization of PMMA + Complex Composites
The L-edges of 3\(d\) transition metals have been relatively underexplored, partly due to their significant surface sensitivity. These edges are highly responsive to variations in coordination and oxidation states and, owing to their reduced intrinsic broadening, provide more detailed insights into the electronic structure of transition metal ions. The spectra for titanium significantly differ in peak position. For powders, two additional tiny features in the pre-edge region were identified (at. ca. 456.4 and 457.3 eV), resulting from dipole forbidden transitions (Figure 4). Figure 4: Normalized XANES spectra of titanium(IV) L\({}_{2,3}\)-edge for powdered samples (P1, P2, P3) collected using the TEY detector and composite materials (K1, K2, K3) with 20% admixture of the studied titanium complexes using an FY detector. Such signals in the range of 456.5-457.5 eV were also observed for TiO\({}_{2}\)[62; 63]. They are not visible for our composites registered in FY mode. It should be noted that the spectra were successfully measured only for the composites with the highest admixture of the studied titanium complex (20%). After dispersing our complexes in a polymeric matrix, those spectra underwent no significant changes, and the shifts are within 0.3 eV. This might indicate the stability of the obtained cores. In all cases, titanium spectra show more intense bands corresponding to the L\({}_{2}\) edge than for the L\({}_{3}\) peaks. In general, there are four main features (Table S2). Peaks at ca. 458 and 461 eV correspond to 2p\({}_{3/2}\rightarrow\) t\({}_{\rm gg}\) and 2p\({}_{3/2}\rightarrow\) e\({}_{\rm g}\) transitions, whereas at ca. 463 and 466 eV they correspond to 2p\({}_{1/2}\rightarrow\) t\({}_{\rm gg}\) and 2p\({}_{1/2}\rightarrow\) e\({}_{\rm g}\), respectively. It should be noted that we cannot distinguish any significant profile change or band splitting for e\({}_{\rm g}\) levels. This effect is quite common, even for TiO\({}_{2}\), and it is ascribed to the splitting of e\({}_{\rm g}\) levels into \(d_{z^{2}}\) and \(d_{x^{2}-y^{2}}\), and the profile change is considered a fingerprint between rutile and anatase [63]. In the reported spectra, a deconvolution was performed in Athena using Gaussian functions, and the results are presented in Table S2. In the case of FY detection mode, the spectra were much noisier, and hence they were smoothed. Nevertheless, no obvious pre-peak was observed, and smoothing did not exclude any peak. The profound structural and topological differences concerning even coordination numbers for the studied titanium complexes resulted in peak position shifts. The separation between t\({}_{\rm gg}\) and e\({}_{\rm g}\) levels is called crystal field splitting (\(\Delta\) parameter). Hence, we can calculate this parameter from L\({}_{3}\) and L\({}_{2}\) edges. In our case, this difference is similar for both edges, being 3.0 and 3.0 for PI, 2.9 and 2.8 eV for P2, 2.3 and 2.4 eV for P3, 3.1 and 3.1 for K1, 3.0 and 3.0 for K2, and 2.3 and 2.2 eV for K3. Hence, we can suppose that both core holes (2p\({}_{3/2}\) and 2p\({}_{3/2}\)) are screened similarly. These data also show that \(\Delta_{\rm oct}\) (almost all titanium atoms were found in an octahedral environment, except for Ti4 in (**1**) and Ti2 in (**2**) [31; 32]) for powders and composites are almost identical, and the changes are tiny (up to 0.2 eV). It also proves that the polymeric matrix did not affect the structure of titanium clusters. Moreover, these data agree well with those determined using the Kubelka-Munk method and theoretical calculations, which were 3.12, 2.96, and 2.39 eV for (**1**), (**2**), and (**3**), respectively [32]. Unfortunately, XANES experiments have only been conducted on titanium complexes, which is primarily due to sample availability and the characteristics of the beamline. Our spectra were measured using soft X-ray radiation, with 2000 eV as the maximum available energy at the PIRX beamline.