O=C(NC(c1ccccc1)c1ccc2ccccc2n1)C1CCN(CCOc2ccc(Cl)cc2)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?