Synthesis, Characterization and Photobiological Studies of Ru(II) Dyads Derived from α-Oligothiophene Derivatives of 1,10-Phenanthroline

Susan Monro, Colin G. Cameron, Xiaolin Zhu, Katsuya L. Colón, Huimin Yin, Tariq Sainuddin, Marc Hetu, Mitch Pinto, Anderson Fuller, Leah Bennett, John Roque, Wenfang Sun, Sherri A. McFarland

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Three new bis(2,2′-bipyridine)-heteroleptic Ru(II) dyads incorporating thienyl groups (n = 1–3, compounds 1, 2 and 3, respectively) appended to 1,10-phenanthroline were synthesized and characterized to investigate the impact of n on the photophysical and photobiological properties within the series. All three complexes showed unstructured emission near 618 nm from a triplet metal-to-ligand charge transfer ( 3 MLCT) state with a lifetime (τ em ) of approximately 1 μs. Transient absorption measurements revealed an additional excited state that was nonemissive and long-lived (τ TA  = 43 μs for 2 and 27 μs for 3), assigned as a triplet intraligand ( 3 IL) state that was accessible only in 2 and 3. All three complexes were strong singlet oxygen ( 1 O 2 ) sensitizers, with quantum yields (Φ ) for 2 and 3 being the largest (74–78%), and all three were photocytotoxic to cancer cells with visible light activation in the order: 3 > 2 > 1. Cell-free DNA photodamage followed the same trend, where potency increased with decreasing 3 IL energy. Compounds 2 and 3 also showed in vitro photobiological effects with red light (625 nm), where their molar absorptivities were <100 m −1  cm −1 . These findings highlight that Ru(II) dyads derived from α-oligothiophenes directly appended to 1,10-phenanthroline—namely 2 and 3—possess low-lying 3 IL states that are highly photosensitizing, and they may therefore be of interest for photobiological applications such as photodynamic therapy (PDT).

Original languageEnglish (US)
Pages (from-to)267-279
Number of pages13
JournalPhotochemistry and Photobiology
Volume95
Issue number1
DOIs
StatePublished - Jan 1 2019

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry

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