O=C(Nc1cccc(C(=O)N2CCN(c3ccc(Cl)cc3)CC2)c1)c1nsc2ccccc12
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?