Synthesis, Characterisation and Biological Evaluation of π-Extended Fe(II) Bipyridine Complexes as Potential Photosensitizers for Photodynamic Therapy

[Display omitted] •Synthesis and characterisation of three π-extended Fe(II) polypyridine complexes.•Investigations of the use of these compounds as chemotherapeutic and photodynamic therapy agents.•Photophysical studies studied revealed absorption in the biological spectral window.•(Photo-)cytotoxicity of the metal complexes in cancerous human cervical carcinoma cells was assessed. Photodynamic therapy (PDT) has received increasing attention over the recent years to treat a variety of cancers. The use of metal complexes as PDT agents is currently a highly investigated alternative due to the attractive chemical and photophysical properties of these compounds. However, most of the metal complexes studied so far are based on rare metals, limiting their use since these metals are neither cheap nor abundant. It would be therefore of high interest to develop compounds based on a cheap, abundant metal. Having this in mind, we designed Fe(II) polypyridine complexes with an absorption in the biological spectral window (600–900 nm) through extension of the π-system. Importantly, the complexes were found to be stable in human plasma and upon light irradiation. A cytotoxic effect in the micromolar range in the dark and a slight effect upon exposure to irradiation at 480 and 540 nm in cancerous human cervical carcinoma (HeLa) cells was observed.