ERROR opening https://cactus.nci.nih.gov/chemical/structure/K%20.K%20.O%3DFe-2%28%3DO%29%28%3DO%29%3DO/file?format=sdf&get3d=True -- K%20.K%20.O%3DFe-2%28%3DO%29%28%3DO%29%3DO could not be loaded.