Spin density characterizations via analysis of variable-temperature tungsten-183 NMR for paramagnetic (4A and 5E) heteropoly complexes. Elucidation of bonding and quantitation of ligand-centered dipolar shifts

Extending Metal‐to‐Polyoxometalate Charge Transfer Lifetimes: The Effect of Heterometal Location

“…The resulting ground electron configuration for 2 a is {…︁[a 1 (Co)] 2 [b 1 (Co)] 1 [b 2 (Co)] 1 [e(Co)] 2 [a 1 (W)] 0 [b 1 (W)] 0 …︁}. It is worth noting that the 1e‐reduction of 2 a yields 1 a , but not a heteropoly blue species, which is also consistent with previous findings 6e…”

“…This provides further evidence that electron transfer from Co II to the polytungstate ligand is responsible for the long‐lived excited state in 1 . Excitation of 2 at 400 nm should only involve the O→Co e transition, as lowering of the Co Td Co e orbitals due to Jahn–Teller distortion6e,g,i,j increases the energy of the Co→W charge transfer transition, while lowering the energy of O→Co charge transfer. The resulting excited state consisting of a hole on an oxygen atom adjacent to a distorted Co II should recombine rapidly.…”

Accessibility of Cation Site in Zeolites by 6Li MAS NMR Spectroscopy Using Paramagnetic O2 as a Chemical Shift Agent. The Example of Zeolite Li-LSX

“…NMR signals of nuclei in the vicinity of paramagnetic species are subjected to large paramagnetic shifts, line broadenings, and short relaxation times T 1 . , The effect arises primarily from hyperfine interactions 9,10 of the unpaired electron spin with the nuclear spin and depends on the configurations of the system paramagnetic species-observed atoms. Paramagnetic shifts are used for instance in lanthanide complexes or transition-metal complexes, to obtain structural information on the conformation of ligands. In the presence of paramagnetic species the T 1 of the 6 Li isotope are strongly reduced. , We take advantage of this effect to obtain spectra of higher signal-to-noise ratio.…”

Methodology to determine the NMR chemical shifts of carbon atoms with radical character: A case of low-spin bis(tert-butylisocyanide) complex of (meso-tetrapropylporphyrinato)iron(III)

“…The δ dip MC values of the 1 H and 13 C nuclei are listed in Table 1. The ligand centered dipolar shift, δ dip LC , is proportional to the π spin density of the observed carbon atom and is given as δ dip LC = Dρ C , where D is a proportional constant [24,25,30,31]. Since the π spin density on the C α atom is considered to be zero, the δ dip LC value should be zero.…”