Multifunctional Magnetic Materials of Organic Origin for Biomedical Applications: A Theoretical Study

Six different diradical systems based on azulene coupler and nitronyl nitroxide radical moieties have been studied theoretically. Among them, three ferromagnetic diradicals are chosen for further calculation to assess their usability in different biological applications such as two-photon absorption photodynamic therapy (TPA-PDT) and magnetic reso nance imaging contrast agents (MRICA). The TPA cross-section values have been calcu lated to judge their efficiency as TPA-PDT photosensitizing agents. Calculated values of TPA cross-section lie in the range of commonly used photosensitizers for PDT. It is seen that the ferromagnetic diradicals can act as very good MRI contrast agents due to their high magnetic anisotropy characteristics. In connection to the magnetic anisotropy, the zero-field splitting (ZFS) parameters are also computed using density functional theory (DFT) based methods. It is found that the proposed diradicals can show good relaxation behaviour and consequently act as efficient MRI contrast agents. Thus, one can anticipate the multifunctional biological activity of these diradicals.