AMMONIUM AND ISOPROPYLAMMONIUM SALTS OF THE FUMARIC-ACID DIANION

The crystal structures of diammonium fumarate, 2NH(4)(+).C4H2O42-, (I) , and bis(isopropylammonium) fumarate, 2C(3)H(7)NH(3)(+).C4H2O42-, (II ), have been determined. The intermolecular N-H ... O hydrogen bonds f orm a three-dimensional network in (I), whereas two-dimensional sheets are formed in (II) separated by layers of isopropyl groups. The N ... O distances are 2.790 (1)-2.903 (1) Angstrom in (I) and 2.747 (1)-2.8 07 (1) Angstrom in (II). Differences between the solid-state photoreac tivities of the fumaric acid ions in (I) and (II) are rationalized bas ed on the crystal structures.