In the crystal structures of both Na+[C1-C6H4-(CH)(2)CO2](-).2H(2)O an
d Mg(H2O)(4)(2+).2[HO-C6H4-(CH)(2)CO2](-), the coordinated cations are
sandwiched between organic layers. Each anion-cation-anion triple lay
er is held together by electrostatic forces and hydrogen bonds and int
eracts with others through van der Waals forces.