O=C(Nc1ccccc1)c1nn(-c2cc(S(=O)(=O)[O-])c([N+](=O)[O-])cc2Cl)[n+](-c2cc(S(=O)(=O)[O-])c([N+](=O)[O-])cc2Cl)n1.[Na+]
A lower number of negative pKa indicates that the acid dissociates more entirely in water. What is the negative pKa of this molecule?