COc1ccc2nc(Nc3nc(O)cc(CSc4nnnn4-c4ccccc4)n3)nc(C)c2c1
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?