Structure and Vibrational Spectra of 1:1 Chloranilic Acid (CLA)—Tetramethylpyrazine (TMP) Complex

Abstract

In searching for new molecular materials the crystals of 1:1 complexes of tetramethylpyrazine (TMP) with chloranilic acid (CLA) were grown. In the crystalline lattice of TMP.CLA infinite chains of hydrogen bonded components are formed. Very strong (d (O···N) = 2.692(2)Å) hydrogen bonds without proton transfer are present. The components of the complex form stacks of parallel arrangement with the distance typical of van der Waals interaction. One can conclude that in packing, interactions via hydrogen bonds play a decisive role. In the IR spectrum one observes a broad, continuous absorption with well resolved trio typical of strong hydrogen bonds. A detailed analysis of IR and Raman spectra in the low frequency region related to deformation vibrations of CH 3 groups shows that strong interaction via hydrogen bonding only slightly affects the dynamics of these groups.

High-temperature protonic motion and low-temperature lattice deformation in one-dimensional hydrogen-bonded molecular chain in tetramethylpyrazine–chloranilic acid (1:1)

“…[11]. This agrees well with the result of X-ray analysis [8,9]. Besides a T 1 dip observed at T c , a steep decrease of T 1 with increasing temperature was observed above 250 K. The slope of the Arrhenius plot corresponds to an activation energy of 35 kJ mol −1 .…”

“…The sample was identified by comparing the observed X-ray powder pattern with the expected one from the crystal data [8,9] …”

“…Similarly to Phz, tetramethylpyrazine (TMP) forms with H 2 ca a 1:1 molecular compound, TMP-H 2 ca, with a supramolecular chain [8,9]. Since the pK a = 2.8 of the conjugate acid of TMP, TMPH + [10], is greater than that of PhzH + , the TMP-H 2 ca is also likely to show a similar neutral-to-ionic phase transition with decreasing temperature.…”

Proton dynamics in one-dimensional hydrogen-bonding system in molecular co-crystals TMP-D2ca and DMP-H2ca

“…The deuterated compound TMP-D 2 ca was obtained by recrystallization from deuterated methyl alcohol, CH 3 OD, by the slow evaporation under nitrogen gas flow. The sample was identified by comparing the observed Xray powder pattern with the expected one from the crystal data [4][5][6]. The extent of the deuteration was estimated to be ca.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 16, 2005) and the discipline

“…Because of the problem of dynamics of CH 3 groups in molecular complexes SawkaDobrowolska et al [92] studied 1:1 chloranilic acid-tetramethylpyrazine complex and its structure. Vibrations related to deformation vibrations of CH 3 groups in IR and Raman spectra show that strong interaction via hydrogen bonding only slightly affects the dynamics of these groups.…”