2025/10/28 by Korusenko, Petr M., Petrova, Olga V., Vereshchagin, Anatoliy A. +8
#Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)
paper · doi:10.48550/arxiv.2510.24149
A detailed study of poly-[Ni(Salen)] polymer in its oxidized (Ox) and reduced (Red) states was conducted using X-ray photoelectron (XPS) and ultraviolet photoemission (UV PES) spectroscopy, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and quantum-chemical calculations. XPS analysis revealed significant energy shifts (-1.5 to -1.8 eV) and broadening of the PE lines for all atoms upon polymerization, indicating a major redistribution of valence electron density between the monomer fragments. In the oxidized polymer, new features in the Ni 2p and O 1s PE spectra were associated with the formation of polarons with weakened Ni-O bonds; this effect diminished upon reduction as the number of polarons decreased. Quantum-chemical calculations attributed the valence band broadening to enhanced C 2p contributions from π-conjugation between monomers. NEXAFS spectroscopy confirmed the stability of the ethylenediamine fragment and the direct involvement of the phenolic rings of the salen ligand in polymerization, also revealing a partial weakening and incomplete restoration of the π bonding between O and Ni atoms upon reduction. Furthermore, it was shown that it is the BF4- anions that weaken the Ni-O bonds during oxidation, which are partially preserved in the reduced state.