O=C(c1ccccc1Cl)N1CCC(c2nc(O)c3nnn(Cc4ccco4)c3n2)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?