COc1ccc(-c2c[nH]nc2-c2ccc(OCc3ccc([N+](=O)[O-])cc3)cc2O)cc1OC
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?