Ammonium squarate salt [(NH
4)
2C
4O
4] crystallizes in the monoclinic space group P2
1/c. The crystal presents the squarate ions displayed in layers parallel to a crystallographic axis and forming hydrogen bonds interactions with
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cations, localized between squarate anions layers. The squarate anion presents similar CC and CO bond distances which indicate a degree of electronic delocalization in the rings. A π-stacking interaction is observed between squarate rings separated by interplanar distance and centroid ring distance of respectively 3.41 and 3.71
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. The electron delocalization was also observed in the vibrational spectra. The infrared spectrum shows a narrow band around 1530 cm
−1, assigned to a coupled stretching mode of CO and CC groups, indicating the high symmetry of the squarate ion. The Raman spectrum also shows this effect in the 1000 to 1200 cm
−1 region (related to CC stretching mode), where it is expected a decrease of the number of bands if compared to squarate ion in aqueous solution, where the symmetry is actually
D4h; in the (NH
4)
2C
4O
4 Raman spectrum just one strong band is observed at 1120 cm
−1. All the vibrational results indicate the symmetry is very close to the one observed for the solvated ion in aqueous solution; once again the vibrational analysis appears as an important tool in recognizing the oxocarbon ion geometry in the solid state.