Lifting of the Degeneracy in Semibullvalenes by Remote and Direct Substituents:  A Quantitative Study Using Variable-Temperature Carbon-13 NMR Spectroscopy†

2001 ◽  
Vol 66 (6) ◽  
pp. 1949-1960 ◽  
Author(s):  
Markus Heubes ◽  
Thomas Dietz ◽  
Helmut Quast ◽  
Maximilian Seefelder ◽  
Alexander Witzel ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Quantitative Study ◽  
Variable Temperature

scholarly journals Spin State Behavior of A Spin-Crossover Iron(II) Complex with N,N′-Disubstituted 2,6-bis(pyrazol-3-yl)pyridine: A Combined Study by X-ray Diffraction and NMR Spectroscopy

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 793
Author(s):  
Elizaveta K. Melnikova ◽  
Dmitry Yu. Aleshin ◽  
Igor A. Nikovskiy ◽  
Gleb L. Denisov ◽  
Yulia V. Nelyubina
Keyword(s):  
Nmr Spectroscopy ◽  
Spin State ◽  
Metal Ion ◽  
Spin Crossover ◽  
Molecular Design ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
High Spin State ◽  
X Ray Diffraction ◽  
X Ray

A series of three different solvatomorphs of a new iron(II) complex with N,N′-disubstituted 2,6-bis(pyrazol-3-yl)pyridine, including those with the same lattice solvent, has been identified by X-ray diffraction under the same crystallization conditions with the metal ion trapped in the different spin states. A thermally induced switching between them, however, occurs in a solution, as unambiguously confirmed by the Evans technique and an analysis of paramagnetic chemical shifts, both based on variable-temperature NMR spectroscopy. The observed stabilization of the high-spin state by an electron-donating substituent contributes to the controversial results for the iron(II) complexes of 2,6-bis(pyrazol-3-yl)pyridines, preventing ‘molecular’ design of their spin-crossover activity; the synthesized complex being only the fourth of the spin-crossover (SCO)-active kind with an N,N′-disubstituted ligand.

scholarly journals Reactions of Dihaloboranes with Electron-Rich 1,4-Bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadienes

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2875
Author(s):  
Li Ma ◽  
Xiaolin Zhang ◽  
Wenbo Ming ◽  
Shengxin Su ◽  
Xiaoyong Chang ◽  
...  
Keyword(s):  
Double Bond ◽  
Nmr Spectroscopy ◽  
Diffraction Analysis ◽  
1H Nmr Spectroscopy ◽  
Variable Temperature ◽  
Organosilicon Compounds ◽  
X Ray Diffraction ◽  
X Ray ◽  
Multinuclear Nmr Spectroscopy ◽  
Bond Character

The reactions of electron-rich organosilicon compounds 1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (2), and 1,1′-bis(trimethylsilyl)-1,1′-dihydro-4,4′-bipyridine (12) with B-amino and B-aryl dihaloboranes afforded a series of novel B=N-bond-containing compounds 3–11 and 13. The B=N rotational barriers of 7 (>71.56 kJ/mol), 10 (58.79 kJ/mol), and 13 (58.65 kJ/mol) were determined by variable-temperature 1H-NMR spectroscopy, thus reflecting different degrees of B=N double bond character in the corresponding compounds. In addition, ring external olefin isomers 11 were obtained by a reaction between 2 and DurBBr2. All obtained B=N-containing products were characterized by multinuclear NMR spectroscopy. Compounds 5, 9, 10a, 11, and 13a were also characterized by single-crystal X-ray diffraction analysis.

scholarly journals Characterizing the Structure and Phase Transition of Li2RuO3 Using Variable-Temperature 17O and 7Li NMR Spectroscopy

2019 ◽  
Vol 31 (8) ◽  
pp. 2814-2821 ◽  
Author(s):  
Philip J. Reeves ◽  
Ieuan D. Seymour ◽  
Kent J. Griffith ◽  
Clare P. Grey
Keyword(s):  
Phase Transition ◽  
Nmr Spectroscopy ◽  
Variable Temperature ◽  
7Li Nmr

Temperature gradients and sample heating in variable temperature high speed MAS NMR spectroscopy

1990 ◽  
Vol 87 (3) ◽  
pp. 592-597 ◽  
Author(s):  
Francisco Aguilar-Parrilla ◽  
Bernd Wehrle ◽  
Hermann Bräunling ◽  
Hans-Heinrich Limbach
Keyword(s):  
Nmr Spectroscopy ◽  
High Speed ◽  
Variable Temperature ◽  
Mas Nmr ◽  
Temperature Gradients ◽  
Sample Heating
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