Reaction of Perrhenate with Phthalocyanine Derivatives in the Presence of Reducing Agents and Rhenium Oxide Nanoparticles in Biomedical Applications

A novel alternative route to access rhenium(V)−phthalocyanine complexes through direct metalation of metal‐free phthalocyanines (H(2)Pcs) with a rhenium(VII) salt in the presence of various two‐electron reducing agents is presented. Direct ion metalation of tetraamino‐ or tetranitrophthalocyanine with perrhenate (ReO(4) (−)) in the presence of triphenylphosphine led to oxidative decomposition of the H(2)Pcs, giving their respective phthalonitriles. Conversely, treatment of H(2)Pcs with ReO(4) (−) employing sodium metabisulfite yielded the desired Re(V)O−Pc complex. Finally, reaction of H(2)Pcs with ReO(4) (−) and NaBH(4) as reducing agent led to the formation of rhenium oxide (Re(x)O(y)) nanoparticles (NPs). The NP synthesis was optimised, and the Re(x)O(y) NPs were capped with folic acid (FA) conjugated with tetraaminophthalocyanine (TAPc) to enhance their cancer cell targeting ability. The cytotoxicity profile of the resultant Re(x)O(y)−TAPc−FA NPs was assessed and found to be greater than 80 % viability in four cell lines, namely, MDA−MB‐231, HCC7, HCC1806 and HEK293T. Non‐cytotoxic concentrations were determined and employed in cancer cell localization studies. The particle size effect on localization of NPs was also investigated using confocal fluorescence and transmission electron microscopy. The smaller NPs (≈10 nm) were found to exhibit stronger fluorescence properties than the ≈50 nm NPs and exhibited better cell localization ability than the ≈50 nm NPs.