Photophysical Properties of a Chiral Iridium-Based Photosensitizer as an Efficient Photodynamic Therapy Agent: A Theoretical Investigation
Abstract
1. Introduction
2. Results and Discussion
2.1. Structural Parameters
2.2. Excitation Energies and Absorption Spectra
2.3. Spin–Orbit Coupling and Intersystem Crossing
2.4. Type I Mechanism
3. Materials and Methods
4. Conclusions
- The optimized geometrical parameters, particularly the Ir-N bond lengths, are in good agreement with experimental X-ray crystallographic data for analogous iridium complexes, validating the computational approach.
- The calculated vertical excitation energies accurately reproduce the experimental absorption spectrum. Notably, the S1 absorption peak at ~470 nm is attributed to an intra-ligand charge transfer from the thiophene substituents to the imidazo-phenanthroline core, consistent with observed optical behavior.
- Spin–orbit coupling between singlet and triplet states, particularly in the S1–T2 and S1–T3 pathways, is sufficient to enable rapid intersystem crossing. This supports an efficient Type II PDT mechanism via singlet oxygen generation.
- Thermodynamic analysis indicates that electron transfer leading to superoxide formation is feasible under certain conditions—specifically when the photosensitizer is in the singlet excited state—suggesting that both Type I and Type II PDT mechanisms are accessible.
- These results position the chiral iridium complex as a versatile and promising candidate for PDT applications. Future work will focus on experimental validation, phototoxicity assessments, and structural optimization to enhance therapeutic performance and selectivity.
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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State | D1 | D2 | D3 | D4 | D5 | D6 |
---|---|---|---|---|---|---|
S0 | 2.187 | 2.187 | 2.070 | 2.016 | 2.016 | 2.070 |
S1 | 2.156 | 2.152 | 2.054 | 2.011 | 2.011 | 2.054 |
T1 | 2.157 | 2.156 | 2.055 | 2.010 | 2.010 | 2.055 |
State | E | λ | f | Transition (%) |
---|---|---|---|---|
T1 | 1.88 | 658.0 | 0.997 | H → L (63.6%) H → L + 1 (26.6%) |
T2 | 2.50 | 495.6 | 0.997 | H → L (25.5%) H → L + 1 (52.5%) H − 2 → L (10.4%) |
T3 | 2.61 | 474.3 | 0.997 | H − 1 → L (44.8%) H − 1 → L + 1 (41.6%) |
S1 | 2.64 | 470.0 | 0.997 | H → L (86.6%) H → L + 1 (9.1%) |
T | ΔE(S₁-Tⱼ) | SOC | kISC |
---|---|---|---|
T1 | 0.74 | 0.28 | 5.73 × 102 |
T2 | 0.03 | 3.95 | 1.77 × 109 |
T3 | −0.07 | 217.76 | 3.71 × 109 |
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Spiegel, M. Photophysical Properties of a Chiral Iridium-Based Photosensitizer as an Efficient Photodynamic Therapy Agent: A Theoretical Investigation. Int. J. Mol. Sci. 2025, 26, 5062. https://doi.org/10.3390/ijms26115062
Spiegel M. Photophysical Properties of a Chiral Iridium-Based Photosensitizer as an Efficient Photodynamic Therapy Agent: A Theoretical Investigation. International Journal of Molecular Sciences. 2025; 26(11):5062. https://doi.org/10.3390/ijms26115062
Chicago/Turabian StyleSpiegel, Maciej. 2025. "Photophysical Properties of a Chiral Iridium-Based Photosensitizer as an Efficient Photodynamic Therapy Agent: A Theoretical Investigation" International Journal of Molecular Sciences 26, no. 11: 5062. https://doi.org/10.3390/ijms26115062
APA StyleSpiegel, M. (2025). Photophysical Properties of a Chiral Iridium-Based Photosensitizer as an Efficient Photodynamic Therapy Agent: A Theoretical Investigation. International Journal of Molecular Sciences, 26(11), 5062. https://doi.org/10.3390/ijms26115062