O=C(C(NS(=O)(=O)c1cccc2nsnc12)c1ccccc1)N1CCN(c2ccccn2)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?