Probing Spin Densities by Use of NMR Spectroscopy

Coordination of 1,4-Diazabutadiene Ligands to Decamethylytterbocene: Additional Examples of Spin Coupling in Ytterbocene Complexes

“…When the δ vs T -1 plots are nonlinear, there is insufficient information in the line shape to postulate a physical process other than some intramolecular process(es) occurring in solution is (are) temperature dependent. A physical process that changes the populations will give rise to the resonances that have nonlinear dependence on T -1 : e.g., geometric changes, intramolecular fluxions, electronic exchange, etc. − In general, our interest is to obtain Δ G ⧧ ( T c ) for chemical exchange processes, and the issue of nonlinearity is not addressed. However, the bipy and related N-heterocyclic complexes present a new challenge, since these ligands in these complexes are radical anions and the effect of electron transfer, spin delocalization, and/or exchange coupling on the line shape must be addressed in a realistic manner.…”

“…(b) Aryl-Substituted Complexes, (C 5 Me 5 ) 2 Yb(dad(H)-R) (R = Aryl). The 1 H NMR data are shown as δ vs T -1 plots, where δ is the observed chemical shift as in earlier papers. − An alternative method of representing the data is to plot the reduced chemical shift (ϑ 298 ) (the chemical shift at a given temperature multiplied by that temperature, δ Τ divided by 298 K in order to get convenient numbers) as a function of T . ,, The latter representations are useful, since they show the relation between solid-state magnetic susceptibility as a function of temperature when plotted as χ T vs T and the reduced chemical shift of a given resonance as a function of temperature, ϑ 298 vs T . , These plots are available as Supporting Information.…”

“…This nonlinear behavior is due to temperature-dependent processes whose populations and chemical shifts depend on temperature. 32 The averaged chemical shift, δav, is the weighted chemical shift of two nuclei, δav ) aδA + bδB. If the populations are unequal, a * b, then δav vs T -1 will be the sum of the individual δA vs T -1 and δB vs T -1 plots, which will be nonlinear if the populations change with temperature.…”

“…geometric changes, intramolecular fluxions, electronic exchange, etc. [31][32][33] In general, our interest is to obtain ∆G ╪ (T c ) for chemical exchange process, and the issue of non-linearity is not addressed. However, the bipy and related N-heterocyclic complexes present a new challenge since these ligands in these complexes are radical anions and the effect of electron transfer, spin delocalization and/or exchange coupling on the line shape must be addressed in a realistic manner.…”

Solid-state high-resolution NMR studies on spin density distribution of a ferromagnetic coordination polymer: Ni(NCS)2(Him)2

“…[3] Higher level of theory and experimental methods to verify this theory are necessary to understand the intermolecular magnetic interaction in coordination compounds. In this work, we have employed Density functional theory (DFT) and NMR experiment [9] to elucidate role of the imidazole ligand in long range ordering.…”