COc1ccc(C2/C(=C(\O)c3ccccc3)C(C)=Nc3nc4ccccc4n32)c(OC)c1
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?