ERROR opening https://cactus.nci.nih.gov/chemical/structure/%5BMg%2B2%5D.%5BO-%5DC%28%3DO%29C.%5BO-%5DC%28%3DO%29C/file?format=sdf&get3d=True -- %5BMg%2B2%5D.%5BO-%5DC%28%3DO%29C.%5BO-%5DC%28%3DO%29C could not be loaded.