Vibrational and crystal structure analysis of a phenylenedioxydiacetic acid derivative

Computationally derived data has successfully assisted the characterisation of the Raman and infrared vibrational spectra of the phenylenedioxydiacetic acid (PDA) derivative 2,2′-[(4-nitro-1,2-phenylene)bis(oxy)]diacetate (I) in the solid state. X-ray diffraction analysis of (I), which crystallised in the non-centrosymmetric achiral space group Pca21, revealed the computationally predicted minimum energy geometry differed to that observed in the solid state molecule due to significant inter-molecular bonding, this was also confirmed computationally. Importantly, large deviations between the wavenumber of predicted and experimental vibrational modes only occurred with functional groups that engaged in inter-molecular bonding. From a comparison of the energies of the calculated and X-ray structural data the crystal packing forces in the solid-state was estimated at ≈240 kJ/mol.