CCc1ccc(Nc2n[n+](-c3ccccc3)c(/C=C/c3ccccc3)s2)cc1.[Cl-]
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?