O=C(c1ccc(Cn2c(=S)[nH]c3cc4c(cc3c2=O)OCO4)cc1)N1CCN(c2ncccn2)CC1
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?