COc1ccc(N2CCN(C(=O)CCCn3c(=S)[nH]c4cc5c(cc4c3=O)OCO5)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?