Another PDT Research Paper joins ever-growing neglected pileLight-responsive and Protic Ruthenium Compounds Bearing Bathophenanthroline and Dihydroxybipyridine Ligands Achieve Nanomolar Toxicity towards Breast Cancer Cells Photochemistry and Photobiology 2021 Aug 19. doi: 10.1111/php.13508. Online ahead of print.
SPECIAL ISSUE RESEARCH ARTICLE
Olaitan Oladipupo 1, Spenser R Brown 2, Robert W Lamb 3 4, Jessica L Gray 1, Colin G Cameron 5, Alexa R DeRegnaucourt 1, Nicholas A Ward 1, James Fletcher Hall 1, Yifei Xu 1, Courtney M Petersen 1, Fengrui Qu 1, Ambar B Shrestha 1, Matthew K Thompson 1, Marco Bonizzoni 1, Charles Edwin Webster 3, Sherri A McFarland 5, Yonghyun Kim 2, Elizabeth T Papish 1
Affiliations
1 Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL, 35487, USA.
2 Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, AL, 35487, USA.
3 Department of Chemistry, Mississippi State University, Mississippi State, MS, 39762, USA.
4 Oak Ridge Institute for Science and Education, Oak Ridge, TN, 37830, USA.
5 Department of Chemistry and Biochemistry, University of Texas, Arlington Arlington, TX, 76019, USA.
Abstract
We report new ruthenium complexes bearing the lipophilic bathophenanthroline (BPhen) ligand and dihydroxybipyridine (dhbp) ligands which differ in the placement of the OH groups ([(BPhen)2 Ru(n,n'-dhbp)]Cl2 with n = 6 and 4 in 1A and 2A , respectively). Full characterization data are reported for 1A and 2A and single crystal X-ray diffraction for 1A . Both 1A and 2A are diprotic acids. We have studied 1A , 1B , 2A , and 2B (B = deprotonated forms) by UV-vis spectroscopy and 1 photodissociates but 2 is light stable. Luminescence studies reveal that the basic forms have lower energy 3 MLCT states relative to the acidic forms. Complexes 1A and 2A produce singlet oxygen with quantum yields of 0.05 and 0.68, respectively, in acetonitrile. Complexes 1 and 2 are both photocytotoxic towards breast cancer cells, with complex 2 showing EC50 light values as low as 0.50 μM with PI values as high as >200 vs. MCF7. Computational studies were used to predict the energies of the 3 MLCT and 3 MC states. An inaccessible 3 MC state for 2B suggests a rationale for why photodissociation does not occur with the 4,4'-dhbp ligand. Low dark toxicity combined with an accessible 3 MLCT state for 1 O2 generation explains the excellent photocytotoxicity of 2.