Solid-state linear polarized IR-spectroscopic and theoretical analysis of methioninamide ester amide of squaric acid diethyl ester

Methioninamide ester amide of squaric acid (1) has been analyzed structurally and IR-spectroscopically by means of ab initio calculations and solid-state linear-polarized IR-spectroscopy (IR-LD) of oriented solid-samples as suspension in nematic liquid crystal. The obtained data are compared with known single crystal X-ray diffraction ones. The experimental IR-spectroscopic bands assignment in solid-state has been reported as well, using reducing-difference procedure for polarized IR-spectra interpretation.