O=C(Nc1ccccc1)c1ccc(Nc2c([N+](=O)[O-])cc([N+](=O)[O-])c3ccccc23)cc1
An acid's negative base-10 logarithmic dissociation constant (pka) follows directly from its underlying thermodynamics; pKa is directly proportional to its standard Gibbs free energy change. What is the pka value of this molecule?