Unexpected XPS binding energy observations further highlighted by DFT calculations of ruthenocene-containing [Irᴵᴵᴵ(ppy)₂(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)₂(FcCOCHCORc)]
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Date
2024
Authors
Buitendach, Blenerhassitt E.
Erasmus, Elizabeth
Fourie, Eleanor
Malan, Frederick P.
Conradie, Jeanet
Niemantsverdriet, J. W. (Hans)
Swarts, Jannie C.
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
The series of iridium(III) complexes, [Ir(ppy)₂(RCOCHCOR′)], with R = CH₃ and R′ = CH₃ (1), Rc (2), and Fc (3), as well as R = Rc and R′ = Rc (4) or Fc (5), and R = R′ = Fc (6), ppy = 2-phenylpyridinyl, Fc = Feᴵᴵ(η⁵–C₅H₄)(η⁵–C₅H₅), and Rc = Ruᴵᴵ(η⁵–C₅H₄)(η⁵–C₅H₅), has been investigated by singlecrystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ ΣχR ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing ΣχR (ΣχR = the sum of Gordy group electronegativities of the R groups on β-diketonato ligands = a measure of electron density on atoms), while in Fe 2p orbitals, XPS binding energy, as expected, increased with increasing ΣχR. Which trend direction prevails is a function of main quantum level, n = 1, 2, 3. . ., sub-quantum level (s, p, d, and f), initial state energies, and final state relaxation energies, and it may differ from compound series to compound series. Relations between DFT-calculated orbital energies and ΣχR followed opposite trend directions than binding energy/ΣχR trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f₇/₂ and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that 1 (IC₅₀ = 25.1 μM) and 3 (IC₅₀ = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC₅₀ = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH₂COCH₃(IC₅₀ = 66.6 μM).
Description
Keywords
Idium, Ferrocene, Ruthenocene, β-diketonato complexes, X-ray photoelectron spectroscopy, DFT calculations, X-ray-induced decomposition, Cytotoxic properties, Antibacterial activity
Citation
Buitendach, B. E., Erasmus, E., Fourie, E., Malan, F. P., Conradie, J., Niemantsverdriet, J. W., & Swarts, J. C. (2024). Unexpected XPS binding energy observations further highlighted by DFT calculations of ruthenocene-containing [Irᴵᴵᴵ(ppy)₂(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)₂(FcCOCHCORc)]. Molecules, 29(22), 5383. https://doi.org/10.3390/molecules29225383