### Atomic and Electronic Structure of Composites Based on [M(Salen)] and Carbon Nanomaterials
In turn, O 1s PE spectra are usually fitted with two [37] or three [103; 134; 135; 137; 138] components of comparable intensities and associated with O 1s binding energies in oxygen-containing groups -CO- (532.0-532.7 eV), -C-O-C- (531.2-531.5 eV), and -C-O-M- (529.7-530.0 eV). Let us now move on to consider the most frequently encountered M 2\(p\) PE spectra of composites with [M(Salen)] complexes in the literature. Unfortunately, the method of energy calibration of M 2\(p\) PE spectra in the studies presented in Table 5 is often not specified. Therefore, it is not possible to carry out a comparative analysis of the energy position of the  
Figure 17: C 1s (a) and N 1s (b) PE spectra of [Ni(Salen)]/rGO. Adapted from Ref. [109] with permission. most intense \(2p_{3/2}\) PE line to estimate the degree of oxidation of the complexing metal in various [M(Salen)] complexes. At the same time, it is known that a change in the energy distance between the \(2p_{3/2}\) and \(2p_{1/2}\) lines (\(dE\)) in the M \(2p\) PE spectra allows one to estimate the degree of oxidation of metals [139]. In view of the above, in order to carry out a more accurate spectral analysis, we assessed not only the energy position of the \(2p_{3/2}\) line but also the \(dE\) values, which are given in Table 5. So, for [M(Salen)] with Co, Cu, and Ni complexing metals, the value of the \(dE\) parameter is in the ranges of 14.7-15.2, 19.9-20, and 17.2-21.2 eV, respectively. It is important to note that the change in \(dE\) for the same complexing metal in composites ([M(Salen)]/ MWCNTs) can be explained by a change in the oxidation state of the metal due to the additional addition of functional groups to the salen ligand (Salfen, (OH)\({}_{2}\)-salen, Toc-(Salen), (3-CH\({}_{3}\)-Salen)). It is noteworthy that composites with [Cu(Salen)] supported on carbon materials showed the same value of \(dE=19.9\) eV for different carbon substrates (MWCNTs and GO), indicating that the carbon substrate has little effect on the charge state of the complexing metal in [Cu(Salen)]. It should be noted that XPS studies of [M(Salen)]/(carbon nanomaterials) composites are not systematic, which leads to an incomplete understanding of changes in the chemical (charge) state of the metal atom and the salen ligand atoms in [M(Salen)] monomers and poly-[M(Salen)] during their deposition on the surface of carbon materials. In addition, the lack of a comprehensive approach, including the study of XPS spectra of all elements in the composite, does not allow us to assess the features of the interaction of nanostructured carbon materials with [M(Salen)] complexes and their derivatives. It is important to note that studies of unoccupied electron states using X-ray absorption spectroscopy, as well as those of the occupied valence electron states using valence photoemission, are still missing for these composites. As a consequence, the lack of these data significantly complicates the development of new highly efficient nanocomposites for various purposes based on monomeric salen complexes or their polymer derivatives and carbon nanostructures.