Synthesis of novel pyridazine-substituted derivatives of natural chlorins

In the present study, a series of novel chlorophyll a derivatives bearing pyridyl-substituted pyridazine residues at various positions of the macrocycle was synthesized via the inverse electron-demand Diels–Alder (IEDDA) reaction. The key photophysical properties of the obtained chlorins were investigated to assess their potential as photosensitizers for photodynamic therapy (PDT). The proposed peripheral design of the macrocycle opens up avenues for the creation of diagnostic metal complexes or polycationic derivatives, underscoring the high potential of these conjugates as multimodal theranostic agents.