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Updated: Sep 10, 2025

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds
Published on: October 18, 2018
Pyridyl-N-Heterocyclic Carbene-Containing cis-[Ni(C6F5)2(N^C)] Complexes─UV-Vis Absorption Spectroscopy and
Rose Jordan1, Noah Sander1, Rebecca Maier1
1Department of Chemistry and Biochemistry, Institute for Inorganic and Materials Chemistry, Faculty of Mathematics and Natural Sciences, University of Cologne, Greinstrasse 6, 50939 Koeln, Germany.
None:
Two Ni(II) complexes, cis-[Ni(C6F5)2(IPy)] (1) and cis-[Ni(C6F5)2(PyImMe)] (2), containing the N^C coordinating pyridyl-N-heterocyclic carbene (NHC) ligands, IPy = 1,3-di(pyridin-2-yl)-imidazole-2-ylidene and PyImMe = 1-(pyridin-2-yl)-3-methyl-imidazole-2-ylidene, were synthesized and analyzed through elemental analysis, 1H and 19F NMR, and HR-ESI-MS(+) mass spectrometry. The diamagnetic complexes show square planar configurations around Ni(II) as shown by single-crystal X-ray diffraction. The geometries were used to benchmark density functional theory (DFT) calculated geometries, which were used for single point and time-dependent DFT (TD-DFT) calculations using the TPSSh functional. The DFT-calculated energy gaps between the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) of about 3 eV agree quite well with the experimental data from cyclic voltammetry with reductions at around -2.1 V and oxidations at around 0.7 V. The TD-DFT calculations model very well the observed UV-vis absorption spectra with characteristic long-wavelength absorptions in the range of 330-450 nm. Comparison with the previously reported [Ni(C6F5)2(bpy)] (bpy = 2,2'-bipyridine) reveals higher LUMO energies, blue-shifted absorptions, a far higher reactivity after one-electron reduction, and a similar reactivity after one-electron oxidation for the complexes 1 and 2 as can be expected from the character of the NHC moiety.
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