COC(=O)/C(=N\N)C(C(=O)C(=O)Nc1cc(Cl)ccc1Cl)c1nc2ccc([N+](=O)[O-])cc2nc1O
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?