O=C(Cn1ncc2c3ccccc3n(Cc3ccc(Cl)cc3)c2c1=O)NCc1ccccn1
An acid's negative base-10 logarithmic dissociation constant (pKa) follows directly from its underlying thermodynamics; the negative pKa is directly proportional to its standard Gibbs free energy change. What is the negative pKa value of this molecule?