O=C(Nc1nnc(CCOCCOCCc2nnc(NC(=O)c3ccco3)s2)s1)c1ccco1
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?