The origin of the splitting of 13C and 15N NMR signals of 3(5)-phenyl-5(3)-methylpyrazolium chloride and bromide in the solid state: Quantum Espresso calculations

• The 13C and 15N CPMAS NMR spectra of two pyrazolium salts have been recorded.
• DFT-D and Quantum Espresso calculations have been performed on the chloride.
• Only Quantum Espresso calculations are able to reproduce the experimental splittings.
• There is a biunivocal relationship between X-ray geometries and SSNMR chemical shifts.

A combination of 13C and 15N CPMAS NMR spectroscopy and theoretical methods (DFT and DFT-D) was used to discuss the observation of large splittings affecting some atoms in 3(5)-phenyl-5(3)-methylpyrazolium chloride and bromide. Conventional calculations using fully optimized structures with C2 symmetry reproduce solution spectra, but the large splitting observed for the signals of several pyrazolium carbon and nitrogen atoms in the solid-state can only be explained by calculations employing the experimental P21/n geometry and periodic boundary calculations.

The origin of the very clear splittings observed for the title compound has been ascertained through Quantum Espresso calculations.Figure optionsDownload as PowerPoint slide