O=C(Cc1cccs1)N1CCCC(c2nc(O)c3nnn(Cc4cccc(Cl)c4)c3n2)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?