Carboxylic acid dianions (fumarate, maleate, and succinate) play a role in coordination chemistry and, to some extent, also in the biochemistry of body cells. An HZB team at BESSY II has now analyzed their electronic structures using RIXS in combination with DFT simulations. The results provide information not only on electronic structures but also on the relative stability of these molecules, which can influence an industry's choice of carboxylate dianions, optimizing both the stability and geometry of coordination polymers.