COc1ccc(N2CCN(Cc3nc(N)nc(Nc4ccc(C)c(Cl)c4)n3)CC2)cc1
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?