COc1cc(NC(=O)CSc2nc3nc(C)c(Cc4ccccc4Cl)c(C)n3n2)cc(OC)c1
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?