The spectroelectrochemistry and voltammetry of Fe(OEP) (NO) in the presence of substituted phenols was studied. Cyclic voltammetry showed that two closely spaced waves were observed for the reduction of Fe(OEP) (NO) in the presence of substituted phenols. The first wave was a single electron reduction under voltammetric conditions. The second wave was kinetically controlled, multielectron process. Visible spectroelectrochemistry of Fe(OEP) (NO) in the presence of substituted phenols showed that three species were present during the electrolysis. Additional spectroscopic studies indicated that the two reduction species were Fe(OEP) (HNO) and Fe(OEP)(HNOH). The Fe(OEP) (HNO) species, which can be generated chemically, was stable over a period of hours. Additional acid did not lead to further protonation. Proton NMR spectroscopy confirmed the Fe(OEP) (HNO) species could be deprotonated under basic conditions. The third species, Fe(OEP)(HNOH), was generated by the further reduction of the chemically generated Fe(OEP) (HNO) complex. Both the Fe(OEP) (HNO) and Fe(OEP)(HNOH) complexes could be slowly oxidized back to Fe(OEP) (NO). At millimolar concentrations of Fe(OEP) (HNO), there was no evidence for the disproportionation of Fe(OEP) (HNO) to Fe(OEP) (NO) and H in the presence of substituted phenols. Nor was there evidence for the generation of NO. The FTIR spectroelectrochemistry showed changes in the infrared spectra in the presence of substituted phenols, but no isotopic sensitive bands were observed for the reduced species between 1450 and 1200 cm. This may be because the ν band shifted into a region (1500-1450 cm) where it would be difficult to observe.

Phosphonium ionic liquids (ILs) have various uses, including as environmentally benign lubricants and lubricant additives. The properties and behavior of these ILs depend on their chemical composition, i.e., cation and anion combination, and the operating conditions. One approach to understanding the relationships between composition, conditions, and lubricant-relevant properties is classical molecular dynamics simulation. Although this research area is still emerging, it is growing rapidly, so a review of the topic is timely.Here, we review force field-based molecular dynamics simulations of phosphonium ILs, with emphasis on physical, chemical, and thermal properties relevant to lubricants. Properties reported in previous studies are density, viscosity, self-diffusivity, ionic conductivity, heat capacity, and thermal stability, as well as interactions with other compounds, including H 2 O and CO 2 , and solid surfaces. The effects of anion and cation, as well as conditions such as temperature, on these properties are identified and analyzed in terms of anion-cation structure, orientation, and interactions. Finally, trends are summarized and opportunities for future research are identified.

The reduction of Fe(OEP)(NO) in the presence of substituted phenols leads to a three‐electron reduction to form Fe(OEP)(NH2OH), which has been characterized by visible spectroscopy and electron stoichiometry. In this work, we have further characterized this species using infrared and 1H NMR spectroscopy, along with DFT calculations. The infrared bands in the 3400–3600 cm–1 region, due to hydroxylamine, were significantly downshifted to the 2500–2700 cm–1 region when 4‐[D1]chlorophenol replaced the normal abundance acid. Using 1H NMR spectroscopy, the hydroxylamine and the meso‐protons were identified. From DFT calculations, the 1H NMR spectra were most consistent with a six‐coordinate complex, Fe(OEP)(NH2OH)(THF).

The 1 H NMR spectra of Fe(OEP)(HNO), which was formed from Fe(OEP)(NO) − in the presence of 3,5dichlorophenol, were studied as a function of temperature. The chemical shift of the HNO proton showed a unique behavior which could be explained based on the equilibrium between the protonated complex, Fe(OEP)(HNO), and the hydrogen-bonded complex, Fe(OEP)(NO) − •••HOPh. This equilibrium was consistent with UV/visible spectroscopy and the voltammetric data. UV/visible stopped-flow experiments showed that the hydrogen-bonded complex, which was formed when weak acids such as phenol were added, and the Fe(OEP)(HNO) complex were quite similar. In addition to the HNO proton resonance, the meso-resonances were consistent with the proposed equilibrium. Density functional theory calculations of various Fe(OEP)(NO) − /Fe(OEP)(HNO) species were calculated, and the results were consistent with experimental data. Synopsis Using 1 H NMR spectra, the equilibrium between Fe(OEP)(HNO) and Fe(OEP)(NO) − hydrogen bonded to phenol was studied as a function of temperature. Voltammetric data, visible spectroscopy, and DFT calculations were used to study this equilibrium.

No abstract