O=[N+]([O-])c1cccc(C(O)/C(=N/Nc2ccccc2)C2Nc3ccc([N+](=O)[O-])cc3N=C2O)c1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?