O=c1cc(CN2CCN(c3cccc(Cl)c3)CC2)c2cc(O)c(-c3ccccc3)cc2o1
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?