Lanthanoid(III) and Actinoid(III) Motexafins in Photodynamic Therapy – a Computational Study on the Electronic Properties of Motexafin Gadolinium

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Lanthanoid(III) motexafins show promise as photosensitizers in photodynamic therapy. This study explores their potential as catalytically active drugs, particularly focusing on Motexafin Gadolinium. The molecular structures of trivalent lanthanoid and actinoid motexafins were optimized using density functional theory, incorporating significant relativistic effects and in vivo conditions through a solvent model. Results align well with existing crystallographic data. The study evaluates vertical and adiabatic ionization potentials, electron affinities, and reduction potentials relative to the standard hydrogen electrode. A systematic mechanism is proposed for generating reactive oxygen species, with Motexafin Gadolinium acting as a catalyst for singlet electron transfer from reducing metabolites, such as ascorbate, to oxygen during radiation therapy. These reactive species, including singlet oxygen and hydrogen peroxide, are vital for inducing apoptosis in cancerous tissues. Additionally, UV/Vis spectra for Motexafin Gadolinium were calculated in both gas and aqueous phases using time-dependent density functional theory. The analysis emphasizes the performance of various functionals regarding long-range charge transfer transitions and the absorption characteristics in the red spectral region, crucial for radiation therapy applications. A detailed comparison of calculated spectra in gas and aqueous solutions, represented by cont