O=C(Nc1ccccc1SCC1CSc2nc3ccccc3c(=O)n21)c1cccc(Cl)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?