O=C(Nc1nnc(-c2c(Cl)c(Cl)c(Cl)c(Cl)c2-c2nc3cc(C(=O)c4ccccc4)ccc3[nH]2)o1)c1ccc(Cl)cc1
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?