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

Abstract

The phase transition of tetramethylpyrazine-chloranilic acid (1:1) was studied by 35 Cl NQR measurements. The frequency splits into a doublet below T c = 83.0 ± 0.5 K. The averaged frequency of 36.98 MHz at 77 K suggests an electrically neutral electronic state of the chloranilic acid molecule, that is, no proton transfer between the acid and base molecules. An enhancement of the relaxation rate was observed at T c : it is presumably due to critical slowing down of a hydrogen motion in the one-dimensional hydrogen bond network. The excitation of a hightemperature hydrogen motion at T > 250 K is also suggested by the steep decrease of T 1 observed above 250 K. From the slope of the Arrhenius plots, an activation energy of 35 kJ mol −1 is calculated for the motion.

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

“…with the critical exponent β = 0.34 ± 0.03 [3] and 0.29 ± 0.07 for TMP-H 2 ca and TMP-D 2 ca, respectively. From the T 1 dip observed at T c , the critical contribution of the spin-lattice relaxation time was estimated and shown to be able to be described by the power law of T − T c ,…”

“…with the critical exponent ζ = 0.7 ± 0.1 [3] and 0.54 ± 0.1 for TMP-H 2 ca and TMP-D 2 ca, respectively. …”

“…For the detection of rather slow motion of proton in the hydrogen-bonding system, NQR spin-lattice relaxation of the nearby atom will be quite sensitive. In the co-crystal of tetramethylpyrazine (TMP) with H 2 ca, TMP-H 2 ca, the spin-lattice relaxation time [3]. In the present paper we studied a possible proton motion in another compound with a similar one-dimensional hydrogen bond, DMP-H 2 ca, the co-crystal between 2,6-dimethylpyrazine (DMP) and H 2 ca (Chart 1).…”

Charge-transfer chemistry of azithromycin, the antibiotic used worldwide to treat the coronavirus disease (COVID-19). Part II: Complexation with several π-acceptors (PA, CLA, CHL)

“…Thereafter, Roy Foster widely discussed and disseminated the concept of CT interactions [ [1] , [2] , [3] , [4] , [5] , [6] ]. A great deal of research has been dedicated to CT interactions due to their wide range of applications in the fields of chemistry, biology, physics, biochemistry, medicine, pharmacology, material science, and industrial technology [ [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] ]. Specifically, in the pharmacology and biochemistry fields, CT interactions contribute to the study of antimicrobial, antitumorigenic, and anti-inflammatory agents, binding mechanisms of pharmaceutical receptors, the thermodynamics and pharmacodynamics of clinical candidate compounds, DNA binding, enzymatic reactions, drug delivery, and quantitively characterizing pharmaceuticals [ [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] ].…”

Nanostructured products of the drug theophylline caused by charge transfer interactions and a binary solvent system: Morphology and nanometry

“…Furthermore, charge-transfer (CT), proton-transfer (PT) and H-bonding interactions between either drugs or biological compounds and small organic or inorganic molecular acceptors have attracted considerable interest because of their unique physical and chemical properties and wide range of applications [1][2][3][4][5][6][7][8][9]. The chemistry of these interactions is an important topic in the pharmacology, chemistry, biology and medicine.…”