O=C(N=Nc1c(O)n(Cc2ccccc2)c2ccccc12)c1cc2ccccc2cc1O
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?