InChI=1S/C16H14N4O4/c1-10(21)18-12-4-2-11(3-5-12)14-7-6-13(24-14)8-17-20-9-15(22)19-16(20)23/h2-8H,9H2,1H3,(H,18,21)(H,19,22,23)/b17-8+