Atomic and electronic structure of poly-[Ni(Salen)]: combined study by XPS, UV PES, NEXAFS and DFT methods

Petr M. Korusenko; Olga V. Petrova; Anatoliy A. Vereshchagin; Oleg V. Levin; Ratibor G. Chumakov; Konstantin P. Katin; Sergey V. Nekipelov; Victor N. Sivkov; Alexandra V. Koroleva; Alexander S. Konev; Alexander S. Vinogradov

arXiv · 2510.24149

Atomic and electronic structure of poly-[Ni(Salen)]: combined study by XPS, UV PES, NEXAFS and DFT methods

Petr M. Korusenko·Olga V. Petrova·Anatoliy A. Vereshchagin·Oleg V. Levin·Ratibor G. Chumakov·Konstantin P. Katin·Sergey V. Nekipelov·Victor N. Sivkov·Alexandra V. Koroleva·Alexander S. Konev·Alexander S. Vinogradov

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Abstract

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 $BF_{4}^-$ anions that weaken the Ni-O bonds during oxidation, which are partially preserved in the reduced state.

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Petr M. Korusenko, Olga V. Petrova, Anatoliy A. Vereshchagin, Oleg V. Levin, Ratibor G. Chumakov, Konstantin P. Katin, Sergey V. Nekipelov, Victor N. Sivkov, Alexandra V. Koroleva, Alexander S. Konev, Alexander S. Vinogradov. 2025-10-28. Atomic and electronic structure of poly-[Ni(Salen)]: combined study by XPS, UV PES, NEXAFS and DFT methods. https://arxiv.org/abs/2510.24149

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