O=S(=O)([O-])c1ccc(N2N=C(c3ccccc3)CC2c2ccccc2)cc1.[Na+]
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?