O=C(CNS(=O)(=O)c1ccccc1)N1CCN(C(=O)c2ccco2)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?