Biotinylated Platinum(II) Ferrocenylterpyridine Complexes for Targeted Photoinduced Cytotoxicity

Biotinylated platinum(II) ferrocenylterpyridine (Fc-tpy) complexes [Pt(Fc-tpy)(L1)]Cl (1) and [Pt(Fc-tpy)(L2)]Cl (2), where HL1 and HL2 are biotin-containing ligands, were prepared, and their targeted photoinduced cytotoxic effect in cancer cells over normal cells was studied. A nonbiotinylated complex, [Pt(Fc-tpy)(L3)]Cl (3), was prepared as a control to study the role of the biotin moiety in cellular uptake properties of the complexes. Three platinum(II) phenylterpyridine (Ph-tpy) complexes, viz., [Pt(Ph-tpy)(L1)]Cl (4), [Pt(Ph-tpy)(L2)]Cl (5), and [Pt(Ph-tpy)(L3)]Cl (6), were synthesized and explored to understand the role of a metal-bound Fc-tpy ligand over Ph-tpy as a photoinitiator. The Fc-tpy complexes displayed an intense absorption band near 640 nm, which was absent in their Ph-tpy analogues. The Fc-tpy complexes (1 mM in 0.1 M TBAP) showed an irreversible cyclic voltammetric anodic response of the Fc/Fc+ couple near 0.25 V. The Fc-tpy complexes displayed photodegradation in red light of 647 nm i...