Structural, Thermal, and Vibrational Properties of N,N-Dimethylglycine-Chloranilic Acid-A New Co-Crystal Based on an Aliphatic Amino Acid

Joanna Hetmańczyk; Łukasz Hetmańczyk; Joanna Nowicka-Scheibe; Andrzej Pawlukojć; Jan K Maurin; Wojciech Schilf

doi:10.3390/ma14123292

Structural, Thermal, and Vibrational Properties of N,N-Dimethylglycine-Chloranilic Acid-A New Co-Crystal Based on an Aliphatic Amino Acid

Materials (Basel). 2021 Jun 14;14(12):3292. doi: 10.3390/ma14123292.

Authors

Joanna Hetmańczyk¹, Łukasz Hetmańczyk¹, Joanna Nowicka-Scheibe², Andrzej Pawlukojć^{3

4}, Jan K Maurin^{5

6}, Wojciech Schilf⁷

Affiliations

¹ Faculty of Chemistry, Jagiellonian University, Gronostajowa 2 Str., 30-387 Cracow, Poland.
² Department of Organic and Physical Chemistry, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Piastów Ave. 42, 71-065 Szczecin, Poland.
³ Institute of Nuclear Chemistry and Technology, Dorodna 16 Str., 03-195 Warsaw, Poland.
⁴ Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141-980 Dubna, Russia.
⁵ National Medicines Institute, Chełmska 30/34 Str., 00-725 Warsaw, Poland.
⁶ National Centre for Nuclear Research, Sołtana 7 Str., 05-400 Otwock, Poland.
⁷ Institute of Organic Chemistry Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw, Poland.

Abstract

The new complex of N,N-Dimethylglycine (DMG) with chloranilic acid (CLA) was synthesized and examined for thermal, structural, and dynamical properties. The structure of the reaction product between DMG and CLA was investigated in a deuterated dimethyl sulfoxide (DMSO-d6) solution and in the solid state by Nuclear Magnetic Resonance (NMR) (Cross Polarization Magic Angle Spinning-CPMAS NMR). The formation of the 1:1 complex of CLA and DMG in the DMSO solution was also confirmed by diffusion measurement. X-ray single crystal diffraction results revealed that the N,N-dimethylglycine-chloranilic acid (DMG⁺-CLA^-) complex crystallizes in the centrosymmetric triclinic P-1 space group. The X-ray diffraction and NMR spectroscopy show the presence of the protonated form of N,N-dimethylglycine and the deprotonated form of chloranilic acid molecules. The vibrational properties of the co-crystal were investigated by the use of neutron (INS), infrared (IR), and Raman (RS) spectroscopies, as well as the density functional theory (DFT) with periodic boundary conditions. From the band shape analysis of the N-CH₃ bending vibration, we can conclude that the CH₃ groups perform fast (τ_R ≈ 10^-11 to 10^‒13 s) reorientational motions down to a temperature of 140 K, with activation energy at ca. 6.7 kJ mol^-1. X-ray diffraction and IR investigations confirm the presence of a strong N⁺-H···O^- hydrogen bond in the studied co-crystal.

Keywords: DFT calculation; N,N-dimethylglycine–chloranilic acid (DMG+–CLA−) co-crystal; X-ray diffraction; inelastic neutron scattering (INS); temperature dependent IR spectroscopy.