O=C(Nc1cccc([N+](=O)[O-])c1)c1ccc2c(c1)C(=O)N(c1ccccn1)C2=O
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?