COc1cc(C(=O)Nc2ccc(-c3nc4ccccc4o3)c(O)c2)cc(OC)c1OC
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?