O=C(Nc1nnc(-c2ccccc2)o1)C(SC(=S)N1CCCCC1)c1ccccc1
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?