Unexpected XPS Binding Energy Observations Further Highlighted by DFT Calculations of Ruthenocene-Containing [Ir<sup>III</sup>(ppy)<sub>2</sub>(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)<sub>2</sub>(FcCOCHCORc)]
The series of iridium(III) complexes, [Ir(ppy)<sub>2</sub>(RCOCHCOR′)], with R = CH<sub>3</sub> and R′ = CH<sub>3</sub> (<b>1</b>), Rc (<b>2</b>), and Fc (<b>3</b>), as well as R = Rc and R′ = Rc (<b>4</b>) or Fc (&l...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-11-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/29/22/5383 |
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| Summary: | The series of iridium(III) complexes, [Ir(ppy)<sub>2</sub>(RCOCHCOR′)], with R = CH<sub>3</sub> and R′ = CH<sub>3</sub> (<b>1</b>), Rc (<b>2</b>), and Fc (<b>3</b>), as well as R = Rc and R′ = Rc (<b>4</b>) or Fc (<b>5</b>), and R = R′ = Fc (<b>6</b>), ppy = 2-phenylpyridinyl, Fc = Fe<sup>II</sup>(η<sup>5</sup>–C<sub>5</sub>H<sub>4</sub>)(η<sup>5</sup>–C<sub>5</sub>H<sub>5</sub>), and Rc = Ru<sup>II</sup>(η<sup>5</sup>–C<sub>5</sub>H<sub>4</sub>)(η<sup>5</sup>–C<sub>5</sub>H<sub>5</sub>), has been investigated by single-crystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ Σχ<sub>R</sub> ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing Σχ<sub>R</sub> (Σχ<sub>R</sub> = 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 Σχ<sub>R</sub>. 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 Σχ<sub>R</sub> followed opposite trend directions than binding energy/Σχ<sub>R</sub> trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f<sub>7/2</sub> and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that <b>1</b> (IC<sub>50</sub> = 25.1 μM) and <b>3</b> (IC<sub>50</sub> = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC<sub>50</sub> = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH<sub>2</sub>COCH<sub>3</sub> (IC<sub>50</sub> = 66.6 μM). |
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| ISSN: | 1420-3049 |