COc1cc(OC)c(C2Oc3nc(SC)nnc3-c3ccccc3N2C(C)=O)cc1OC
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?