In this study, the effect of fluorine upon the heme-binding ability of the xanthone nucleus was investigated for 3,6-bis-(omega-N,N-diethylaminoamyloxy)-4,5-difluoroxanthone (F2C5). 2-Fluoro-1,3-dimethoxybenzene was prepared by a new, improved method and used to build up the xanthone nucleus. The interaction of F2C5 with heme was investigated by UV-vis, (1)H NMR, and (19)F NMR spectroscopy. For the first time, NMR studies for the heme-drug interactions are carried out at pH 5.0, physiological for the acidic food vacuole of the malaria parasite.