Axial Ligand Effects on the Mechanism of Ru-CO Bond Photodissociation and Photophysical Properties of Ru(II)-Salen PhotoCORMs/Theranostics: A Density Functional Theory Study
Density functional theory (DFT) calculations were employed to study a series of complexes of general formula [Ru(salen)(X)(CO)]<sup>0/−1</sup> (X = Cl<sup>−</sup>, F<sup>−</sup>, SCN<sup>−</sup>, DMSO, Phosphabenzene, Phosphole, TPH, CN<sup>−<...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/5/1147 |
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| Summary: | Density functional theory (DFT) calculations were employed to study a series of complexes of general formula [Ru(salen)(X)(CO)]<sup>0/−1</sup> (X = Cl<sup>−</sup>, F<sup>−</sup>, SCN<sup>−</sup>, DMSO, Phosphabenzene, Phosphole, TPH, CN<sup>−</sup>, N<sub>3</sub><sup>−</sup>, NO<sub>3</sub><sup>−</sup>, CNH<sup>−</sup>, NHC, P(OH)<sub>3</sub>, PF<sub>3</sub>, PH<sub>3</sub>). The effect of ligands X on the Ru-CO bond was quantified by the <i>trans</i>-philicity, Δ<i>σ</i><sup>13</sup>C NMR parameter. The potential of Δ<i>σ</i><sup>13</sup>C to be used as a probe of the CO photodissociation by Ru(II) transition metal complexes is established upon comparing it with other <i>trans</i>-effect parameters. An excellent linear correlation is found between the energy barrier for the Ru-CO photodissociation and the Δ<i>σ</i><sup>13</sup>C parameter, paving the way for studying photoCORMs with the <sup>13</sup>C NMR method. The strongest <i>trans</i>-effect on the Ru-CO bond in the [Ru(salen)(X)(CO)]<sup>0/−1</sup> complexes are found when X = CNH<sup>−</sup>, NHC, and P(OH)<sub>3</sub>, while the weakest for X = Cl<sup>−</sup>, NO<sub>3</sub><sup>−</sup> and DMSO <i>trans</i>-axial ligands. The Ru-CO bonding properties were scrutinized using Natural Bond Orbital (NBO), Natural Energy Decomposition Analysis (NEDA) and Natural Orbital of Chemical Valence (NOCV) methods. The nature of the Ru-CO bond is composite, i.e., electrostatic, covalent and charge transfer. Both donation and backdonation between CO ligand and Ru metal centre equally stabilize the Ru(II) complexes. Ru-CO photodissociation proceeds via a <sup>3</sup>MC triplet excited state, exhibiting a conical intersection with the T<sub>1</sub> <sup>3</sup>MLCT excited state. Calculations show that these complexes show bands within visible while they are expected to be red emitters. Therefore, the [Ru(salen)(X)(CO)]<sup>0/−1</sup> complexes under study could potentially be used for dual action, photoCORMs and theranostics compounds. |
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| ISSN: | 1420-3049 |