Towards Long Wavelength Absorbing Photodynamic Therapy Photosensitizers via the Extension of a [Ru(bipy)3]2+ Core

Abstract

Complementary to classical treatment methods used against cancer, photodynamic therapy (PDT) has received increasing attention over the last years. PDT relies on the generation of reactive oxygen species (ROS) upon light irradiation to trigger cell death. As the wavelength employed during such treatments directly influences the light penetration depth and therefore the possibility to treat deep seated tumors or large tumors, research efforts have been made towards the development of photosensitizers (PSs) with an absorption in the phototherapeutic window (600–900 nm). To tackle this drawback, we report herein the preparation and characterization of new RuII‐containing PDT PSs, that are based on a [Ru(bipy)3]2+ core (1; bipy: 2,2′‐bipyridine) and that are extended with methyl groups (2) or vinyl dimethylamino groups (3). As anticipated with our design, we found a red‐shift of 65 nm of the maximum absorption of complex 3 in comparison to complex 1. In addition, we report on the in‐depth photophysical properties as well as (photo‐)cytotoxicity against cervical cancerous HeLa cells of the investigated compounds.