O=C(O)CCC(=O)Nc1ccc(-c2csc(Nc3cccc4ccccc34)n2)cc1
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?