O=C1CSC2(CC(/C=C/C=C/c3ccccc3)=NN2c2cccc(S(=O)(=O)O)c2)N1c1nc2ccccc2s1
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?