The infrared and Raman spectra of crystalline squaric acid

Supramolecular structure of the 1:2 complex of 1,4-dimethylpiperazine mono-betaine with squaric acid

“…A similar broadening of the absorption in this region is observed in the spectrum of squaric acid (44) and in the spectra of its complexes with various bases (21, 23, 33, 35, 45 -47). This broad band overlaps the dCH 3 , dCH 2 , dOH, gCH 3 , gCH 2 and gOH vibrations.…”

Crystal data, optics and vibrational spectra of potassium hydrogen squarate monohydrate, KHC4O4�H2O

“…Relatively few bands were found (contrast the Raman spectra, tables 1 and 2), but the frequencies bore some similarity to those found in the acid by Baglin & Rose (1970), and repeated by us, and in the ion (dipotassium salt) by Ito & West (1963). There is no complete band-for-band identity to suggest a superposition of ion and acid spectra.…”

Vibrational characterization of poly(1‐methylpyrrole‐ co‐squaric acid) and poly(1‐dodecylpyrrole‐co‐squaric acid) by enhanced Raman spectroscopy

“…The band at 1330 cm 1 , observed in the squaric acid spectrum, but absent in the squarate anion spectrum, can be assigned to the OH bending modes. 22 Analogous assignment can be made for the bands observed at 1330 cm 1 (PMPS) and 1357 cm 1 (PDPS), indicating the presence of OH groups in the polymeric structures. This observation confirms the protonation of the squarate moiety in the polymeric chains, corroborating the repetitive unit proposed.…”