Spectroscopic and theoretical study of the 1,2,3-Triazole-4,5-dicarbonitrile anion and its lithium ion pairs

The lithium cation coordination to the 1,2,3-Triazole-4,5-dicarbonitrile (TADC) anion was studied using Raman spectroscopy and ab initio SCF-MO Hartree-Fock (HF) calculations. Three stable 1:1 ion pair complex geometries were found, one transition state (TS) and two local minima, all of which having comparable lithium binding energies. The binding energies were further evaluated using single point calculations with larger basis sets and electron correlation: HF/6-311+G*//HF/6-31G* and LMP2/6-31G*//HF/6-31G*. By comparing theoretical spectra with both polarised and depolarised Raman spectra of the pure lithium salt of TADC and salt solutions, a preference for bi-dentate lithium ion coordination to the nitrogen atoms in the planar five-member ring was revealed. Finally, comparisons with other previously calculated coordination strengths for lithium ion–anion 1:1 systems were made.