Pulsed electron paramagnetic resonance (EPR) dipolar spectroscopy (PDS) offers several methods for measuring dipolar coupling constantsa nd thus the distance between electron spin centers. Up to now,P DS measurements have been mostly applied to spin centers whose g-anisotropies are moderatea nd therefore have an egligible effect on the dipolar coupling constants. In contrast, spin centers with large g-anisotropy yield dipolarc oupling constants that depend on the g-values.I nt his case, the usual methods of extracting distances from the raw PDSd ata cannot be applied. Here, the effect of the g-anisotropyo nP DS data is studied in detail on the example of the low-spin Fe 3 + ion. First, this effect is described theoretically,u sing the work of Bedilo andM aryasov (Appl. Magn. Reson. 2006,3 0, 683-702) as ab asis. Then, two knownF e 3 + /nitroxide compounds and one new Fe 3 + /trityl compound were synthesized and PDS measurements were carried out on them using am ethod called relaxation inducedd ipolarm odulation enhancement (RIDME). Based on the theoretical results, aR IDME data analysis procedure was developed, which facilitated the extraction of the inter-spin distance and the orientation of the inter-spin vector relative to the Fe 3 + g-tensor frame from the RIDME data. The accuracyo ft he determined distances and orientationsw as confirmed by comparison with MD simulations. This methodc an thus be appliedt ot he highly relevant class of metalloproteins with, for example, low-spin Fe 3 + ions.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.org/10.

The first example of a ring opening reaction of a 1,2-oxaphosphetane complex is reported, i.e., water in the presence of [Li(12-crown-4)]Cl furnished a C-OH functional phosphinito complex. Employment of the latter in ring forming reactions with MeECL (E = Si, Ge) using different nitrogen bases is also described.

Iron(III) porphyrins have the propensity to form μ2‐oxo‐dimers, the structures of which resemble two wheels on an axle. Whereas their crystal structure is known, their solution structure and internal dynamics is not. In the present work, the structure and dynamics of such dimers were studied by means of electron paramagnetic resonance (EPR) spectroscopy and quantum chemistry based molecular dynamics (MD) simulations by using the semiempirical tight‐binding method (GFN‐xTB). To enable EPR investigation of the dimers, a nitroxide was attached to each of the tetraphenylporphyrin cores through a linear and a bent linker. The inter‐nitroxide distance distributions within the dimers were determined by continuous‐wave (cw)‐EPR and pulsed electron–electron double resonance (PELDOR or DEER) experiments and, with the help of MD, interpreted in terms of the rotation of the porphyrin planes with respect to each other around the Fe–O–Fe axis. It was found that such rotation is restricted to the four registers defined by the phenyl substituents. Within the registers, the rotation angle swings between 30° and 60° in the proximal and between 125° and 145° in the distal register. With EPR, all four angles were found to be equally populated, whereas the 30° and 145° angles are strongly favored to the expense of the 60° and 125° angles in the MD simulation. In either case, the internal dynamics of these dimers thus resemble the motion of a step motor.

Tricyclic 1,4-dihydro-1,4-phosphasilines 3a,b were synthesized from Si(NR2)2-bridged compounds 2a,b. Based on calculated FMOs of 3b, forecasting a possible P-selective P-N bond cleavage reduction, a redox cycle could be established using...

This feature article highlights the discovery and development of phosphanoxyl complex chemistry starting from (neutral) low-coordinate phosphorus radicals and the quest of metal ligation effects. We describe synthesis and reactions...