O=C(CSc1ccc2nnc(CCNS(=O)(=O)c3ccccc3)n2n1)Nc1nc2ccccc2s1
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?