Although C1s core ionization energies and 13 C-NMR chemical shifts are different spectroscopic techniques, they both provide valuable insights into the chemical environment of carbon atoms within the same compound. Despite their distinct measurement principles, they share a common goal of probing the molecular structure, making them complementary tools for characterizing carbon atoms. C1s core ionization energies, typically measured through techniques like X-ray photoelectron spectroscopy (XPS), reveal information about the energy required to remove an electron from the 1s orbital of a carbon atom. This energy is influenced by factors such as the local electronic environment, including neighboring atoms and functional groups, as well as structural features like bond lengths and angles. Consequently, variations in C1s ionization energies across different carbon atoms within a molecule reflect differences in their chemical surroundings. On the other hand, 13 C-NMR chemical shifts provide information about the local magnetic environment of carbon atoms. When a carbon atom is placed in a magnetic field, its nuclei exhibit resonance frequencies that are influenced by the electronic environment surrounding the carbon nucleus. Chemical shifts in the NMR spectrum result from differences in electron density distribution and magnetic shielding effects caused by neighboring atoms and functional groups.