“…The free acid of tiron has been used in an aqueous flow battery because of its two-electron redox couple within range of an aqueous system, high water solubility, and low cost (Yang et al, 2014). When crystallized, tiron molecules can form a network through coordination of the counter-cation to the sulfonate or protonated or deprotonated hydroxide of the tiron (Cô té & Shimizu, 2001Sheriff et al, 2003;Guan & Wang, 2016, 2017. These networks can range from onedimensional networks, which form a linear polymer (Cô té & Shimizu, 2003;Sheriff et al, 2003), to three-dimensional networks in which each tiron anion is coordinated to a metal cation and forms an interconnected lattice among all tiron anions in the crystal (Cô té & Shimizu, 2001Guan & Wang, 2016).…”