Synthesis and Structural Investigation of Brightly Colored Organoammonium Violurates

Nine new organoammonium violurates [ R 1 R 2 R 3 NH][C 4 H 2 N 3 O 4 ] [ R 1 = R 2 = H, R 3 = c ‐C 3 H 5 ( 2 ), R 3 = t Bu ( 3 ), R 3 = adamantyl ( 4 ), R 3 = C 6 H 2 Me 2 ‐4,5‐NH 2 ‐2 ( 5 ); R 1 = H, R 2 = R 3 = Et ( 6 ), i Pr ( 7 ); R 1 = H, R 2 / R 3 = (–CH 2 –) 4 ( 8 ); R 1 = R 2 = R 3 = Et ( 9 ); R 1 = R 2 = Me, R 3 = (CH 2 ) 2 NMe 2 ( 10 )] were prepared by treatment of violuric acid ( 1 ) with a variety of primary, secondary, and tertiary amines. With the exception of orange 5 , all these violurate salts form bright blue or blue‐purple crystalline solids. The acidic triethylammonium violurate [NHEt 3 ]H[C 4 H 2 N 3 O 4 ] 2 · H 2 O ( 9a ) was isolated in the form of red‐violet, plate‐like crystals by the reaction of violuric acid hydrate with triethylamine in a molar ratio of 2:1 in ethanol. All compounds were fully characterized by their IR and NMR ( 1 H, 13 C) data as well as elemental analyses. X‐ray crystal structures determinations of 2 , 7 , and 9a revealed supramolecular self‐assembly through networks of N–H ··· N and N–H ··· O hydrogen bonds in the crystalline state.