NC(=O)c1cc[n+](CC(=O)c2ccc(NC(=O)c3ccccc3)cc2)cc1.[Br-]
The negative base-10 logarithmic of dissociation constant (pka) for an acid is a direct consequence of the underlying thermodynamics of the dissociation reaction; the pKa value is directly proportional to the standard Gibbs free energy change for the reaction. What is the pka value of this molecule?