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

Abstract

The title compound 4a has been prepared by slow evaporation of an equimolar mixture of 2,4,6-trimethylbenzoic acid (mesitylenecarboxylic acid) and 3,5-dimethylpyrazole. Two pyrazoles and two benzoic acids form a tetramer unit through N–H ⋯ O and O–H ⋯ N hydrogen bonds. The pyrazole rings in 4a show standard geometries. Variable temperature ¹⁵N CPMAS NMR experiments showed that no dynamic process takes place in 4a, which is consistent with results of low temperature (77 K) FTIR spectroscopy. This fact can be explained taking into account the acid–base properties of both components.