O=[N+]([O-])c1ccc(C(c2sc3nc(-c4ccco4)nn3c2O)N2CCN(c3cccc(Cl)c3)CC2)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?