Theoretical study of C6F5-corrole molecules functionalized with aromatic groups for Photodynamic Therapy

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2023-05, Vol.293, p.122500, Article 122500
• Main Authors: da Rocha, Vinícius N., Köhler, Mateus H., Nagata, Khayth, Piquini, Paulo C.
• Format: Article
• Language: English
• Subjects: Corrole; Intersystem crossing; Molecular docking; Photodynamic therapy
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2023.122500

The singlet oxygen generation by electronically excited molecules in photodynamic therapy (PDT) requires light absorption within a specific wavelength window, and a subsequent intersystem crossing transition to a triplet excited state that is, at least, 0.98 eV higher in energy than the singlet ground state. Tetrapyrrolic macrocycles, such as porphyrin and corrole, have been widely used in oxygen singlet generation for PDT. Suitable functionalization can potentialize these macrocycles as photosensitizers. In this contribution, we use Density Functional Theory (DFT) calculations to determine the structural, electronic and spectroscopic properties of corrole macrocycles bound to different polycyclic aromatic groups in the gas phase, dichloromethane, and water. We also calculate the spin–orbit coupling (SOC) matrix elements of the intersystem crossing channels involving the first excited singlet states and excited triplet states. The results for optical absorption show that the threshold wavelength for optical absorption increases with the polarity of the environment and the number of aromatic rings of the ligands, whereas the oscillator strengths increase with the polarity of the environment but decrease with the number of aromatic rings. It is verified that the triplet excited states involved in the intersystem crossing transitions satisfy the energy requirement for the oxygen singlet generation. The magnitude of spin–orbit coupling (SOC) matrix elements associated with the intersystem crossing are also seen to be dependent on the environment involving the corrole molecules, and on the number of aromatic rings of the ligands connected to the corrole. Further, the binding of the functionalized corrole molecules with biomolecules as the calf thymus DNA and human serum albumin is studied and characterized through molecular docking. These results show that the corrole macrocycles, suitably functionalized with polycyclic aromatic groups, fulfill several criteria to be considered as good PDT photosensitizers. [Display omitted] •Optical absorption of the functionalized corrole molecules at the therapeutic window.•Spin–orbit coupling matrix elements between singlet and triplet excited states large enough to the occurrence of intersystem crossing.•Binding of the corrole molecules with human serum albumin and calf thymus DNA.