COc1ccc(C(=O)NC(=S)Nc2ccccc2N2CCN(S(C)(=O)=O)CC2)cc1OC
An acid's negative base-10 logarithmic dissociation constant (pka) follows directly from its underlying thermodynamics; pKa is directly proportional to its standard Gibbs free energy change. What is the pka value of this molecule?