It Takes Three to Tango: The Length of the Oligothiophene Chain Determines the Nature of the Long‐Lived Excited State and the Resulting Photocytotoxicity of a Ruthenium(II) Photodrug

Abstract

TLD1433 is the first Ru(II) complex to be tested as a photodynamic therapy agent in a clinical trial. In this contribution we study TLD1433 in the context of structurally‐related Ru(II)‐imidozo[4,5‐f][1,10]phenanthroline (ip) complexes appended with thiophene rings to decipher the unique photophysical properties which are associated with increasing oligothiophene chain length. Substitution of the ip ligand with ter‐ or quaterthiophene changes the nature of the long‐lived triplet state from metal‐to‐ligand charge‐transfer to 3ππ* character. The addition of the third thiophene thus presents a critical juncture which not only determines the photophysics of the complex but most importantly its capacity for 1O2 generation and hence the potential of the complex to be used as a photocytotoxic agent.

A Molecular Photosensitizer in a Porous Block Copolymer Matrix‐Implications for the Design of Photocatalytically Active Membranes

“…Monitoring the emission at 620 nm, a 3 MLCT lifetime of 350 ns was determined for [Ru(bpy) 2 (ipPhNH 2 )] 2+ in H 2 O (Figure 4b). Again this value is in good agreement with 3 MLCT lifetimes, for example, observed for [Ru(bpy) 3 ] 2+ and [Ru(bpy) 2 ip] 2+ [25,29] . In the Ru‐membrane, the emission signal decays bi‐exponentially with lifetimes of 90 and 750 ns (Figure 4b).…”

String-Attached Oligothiophene Substituents Determine the Fate of Excited States in Ruthenium Complexes for Photodynamic Therapy

“…The UV−vis absorption and emission spectra were reported previously. 29 The ratio of the rR band intensity at 1450 cm −1 (due to bpy) relative to that at 1320 cm −1 (due to the thienyl rings) is indicated by the red circles and shows the increased contribution of the thienyl vibration with increasing n for Ru-ip-0T-4T with 476 nm excitation. (c) rR spectra (normalized to the bpy band at 1320 cm −1 ) of Ru-ip-0T-4T in water with 476 nm excitation.…”

“…We highlight the primary photoinduced processes leading to the population of the photobiologically relevant long-lived triplet states that were detailed in a previous study, where it was shown that the singlet oxygen quantum yields increase (and emission quantum yields decrease) with the length of the thiophene chain. 29 Here, we explore the Ru-ip-nT (n = 0−4) series and show the impact of the initial excitation wavelength on the excited-state relaxation pathway and the population of the long-lived excited states. 29…”

“…29 Here, we explore the Ru-ip-nT (n = 0−4) series and show the impact of the initial excitation wavelength on the excited-state relaxation pathway and the population of the long-lived excited states. 29…”

Merging of a Perylene Moiety Enables a RuII Photosensitizer with Long‐Lived Excited States and the Efficient Production of Singlet Oxygen

“…Interestingly, transient absorption (tA) spectroscopy revealed three lifetimes of 600 ns and 1500 ns as well as a long lifetime of 8 μs for RuipPer in acetonitrile solution under inert conditions (Figure 5), which is similar to other multichromophoric Ru II complexes. [32,38,72] The transient absorption spectrum of RuipPer has two excited state absorptions (ESA between 360 and 380 nm as well as at 450 nm; Figure 5). In addition, two ground state bleaches (GSB) until 440 and 500 nm can be seen.…”