Lithium-pyrazole-3,4,5-tricarbonitrile:: Ion pairing and lithium ion affinity studies

Negative charge stabilized by ring delocalization on five-membered rings is a practical and theoretically interesting alternative to conventional fluorine-based anions. Coordination of the lithium cation to the pyrazole-3,4,5-tricarbonitrile (PATC) anion was studied using vibrational spectroscopy (Raman and IR) and ab initio SCF-MO Hartree--Fock (HF) calculations. Four 1:1 ion pair geometries were found, one being energetically more stable. By comparing theoretical spectra with both IR and Raman spectra of salt solutions, it was found that the lithium ion favors bidentate coordination to the ring nitrogen atoms, as suggested by the binding energies. Finally, comparisons were made with previously calculated coordination strengths for other similar lithium anion 1:1 systems.