O=C(NCc1ccc2c(c1)OCO2)C12CN(Cc3ccccc3)CC1C(c1cccc([N+](=O)[O-])c1)=NO2
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?