PS-33-1 Poster Session Acta Cryst. (2021), A77, C1013 Structure activity relationship of imidazo[4,5-f] ligands and their Rhenium(I) complexes- photoluminescence and DNA intercalation L.E. Kapp, M. Schutte-Smith, H. G. Visser University of the Free State, Bloemfontein, South Africa lucy.kapp@gmail.com Photodynamic therapy (PDT) involves the treatment of a patient with a non-toxic photosensitiser. Upon irradiation by an external light source (600-850 nm)[1,2], the photosensitiser causes the production of singlet oxygen radicals at the tumour site which in turn provokes destruction of the tumour and so arousing significant interest as a potential cancer treatment.[3] Notably, a range of Rhenium(I) tricarbonyl complexes were found to induce cell death in a manner recognisably different to that of cisplatin and overcome cisplatin resistance in several resistant cell lines.[4,5] It has become apparent that 1,10-phenanthroline moieties show favourable fluorescence for the detection of metal ions.[6] Sensors based on the 1,10-phenanthroline moiety coordinated to various metal ions have resulted in compounds exhibiting strong fluorescent properties. El-Awady et al. reported the effects of imidazopyridine derivative binding to DNA. They found that this introduction resulted in apoptosis in lung and breast cancer cells.[7] Thapa et al. synthesised a range of phenanthroline-type derivatives. Structure- activity relationship studies of these phenanthroline-type derivatives confirmed the importance of a [2,2’;6,2”]-terpyridine skeleton for cytotoxicity toward several cancer cell lines.[8] A range of imidazo[4,5-f]-1,10-phenananthroline type ligands were synthesised and coordinated to Rhenium(I) yielding compounds of the general formula [Re(CO) 3 (N,N’)(H 2 O)] + where N,N’ is the imidazo[4,5-f]-1,10-phenananthroline type ligand. These ligands and complexes were characterised by multinuclear NMR spectroscopy and IR Spectroscopy. X-ray crystallography data has been obtained for several ligands thus far. The photoluminescent, as well as the DNA binding capacity to calf thymus DNA were studied. Figure 1. Crystal structure of the imidazo[4,5-f]1,10-phenanthroline type ligands, (2.6-dimethoxypyridyl)imidazo[4,5-f]1,10- phenanthroline and (benzo[b]thiophene)imidazo[4,5-f]1,10-phenanthroline. [1] Wähler, K., Ludewig, A., Szabo, P., Harms, K., Meggers, E. (2014). Eur. J. Inorg. Chem. 807. [2] Robertson, C. A., Hawkins-Evans, D., Abrahamse, H. (2009). J Photochem. Photobiol. B: Biology. 96, 1. [3] Castano, A. P., Demidova, T. N., Hamblin, M. R. (2005). Photodiag. Photodyn. Ther. 2, 1. [4] Knopf, K. M., Murphy, B. L., MacMIllan, S. N., Baskin, J. M., Bar, M. P., Boros, E., Wilson, J. J. (2017). J. Am. Chem. Soc. 139, 14302. [5] Konkankit, C. C., King, A. P., Knopf, K. M., Southard, T. L., Wilson, J. J. (2019). ASC Med. Chem. Lett. 10, 822. [6] Larsen, A. F., Ulven, T. (2011). Org. Lett. 13, 3546. [7] El-Awady, R. A., Semreen, M. H., Saber, M. M., Cyprian, F., Menon, V., Al-Tel, T. H. (2016). DNA Repair. 37, 1. [8] Thapa, P., Radha, K., Han, Y. Y, Pil-Hoon, P., Eunyoung, L., Kyung-Hwa, J., Younghwa, N., Won-Jea, C., Youngjoo, K., Eung-Seok, L. (2020). Bioorg. Chem. 40, 67. Keywords: Photodynamic therapy; Rhenium; Fluorescence; 1,10-phenanthroline; Structure activity relationship This work is based on the research supported wholly by the National Research Foundation of South Africa.