COc1ccc(C)cc1Nc1n[n+](-c2ccccc2)c(-c2c(Cl)cccc2Cl)s1.[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?