Using insights obtained from probe molecule studies and analysis of molecular analogs, supplemented by the additional information arising from DFT calculations, we turned back our attention to understanding the NMR signal of the supported materials ( 15 N-py/Ga@SiO2 and Ga@SiO2). We thus chose to model the NMR spectra with the extended Czjzek model (ECM) considering the presence of two sites. The ECM is characterized by three parameters: 𝜂 0 and 𝐶 𝑄,0 which define the local geometry of the site, and 𝜀, a measure for the perturbation of the well-defined site by Czjzek-noise.