ERROR opening https://cactus.nci.nih.gov/chemical/structure/%5BO-2%5D.%5BHg%2B%5D%20%5BHg%2B%5D/file?format=sdf&get3d=True  -- %5BO-2%5D.%5BHg%2B%5D%20%5BHg%2B%5D could not be loaded.