Mixed crystals of pyrazoles and benzoic acids. Part 1. The molecular structure of 3,5-dimethylpyrazole–2,4,6-trimethylbeflzoic acid co-crystals

Pyrazoles as molecular probes to study the properties of co-crystals by solid state NMR spectroscopy

“…Pyrazoles and particularly 3,5-dimethylpyrazole (1), show a dynamic process in the solid state that consists in the transfer, generally concerted, of several protons between the nitrogen atoms [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. This process (named SSPT, Solid State Proton Transfer) is illustrated in Fig.…”

The structure of 3,5-dimethylpyrazole/carboxylic acids co-crystals

“…MHz) we obtain a signal at -182.8 ppm (-181.7, N-H [6]) and two signals at -116.8 and -113. None of these structures explain the observed chemical shifts for 1 2 3 2 .…”

“…Recently, we have proved 5 that in the case of imidazoles [HBD, the N(1)-H and HBA, the -N(3)= sites] only the 4,5-dimethylimidazole was able to disrupt the trimer 1 3 formed by 3,5-dimethylpyrazole in the solid state. As a continuation of our work concerning the determination of the X-ray molecular structure of 3,5-dimethylpyrazole (1)-2,4,6-trimethylbenzoic acid (2) cocrystal, 6 in the present paper we report a study concerning carboxylic acids (HBD, the O-H and HBA, the O= sites). This complex crystallizes forming a tetramer 1 2 2 2 ( Figure 2) and, although a quadruple proton transfer is possible, such SSPT was not observed by solid-state 15 N NMR.…”

A simple but highly selective and sensitive fluorescence reporter for toxic CdII ion via excimer formation

“…Several different starting geometries have been considered for the geometry optimization to ascertain that the optimized structures correspond to a global minimum. On literature survey we know that O-H· · ·O hydrogen bonding distance in benzoic acid dimer is 1.64Å [44]. However, in case of KA-dimer, stable H-bonding between the two -COOH groups is available at a distance 1.61Å ( Figure S7b).…”