N-Substituted salicylaldimine complexes of iron(III). II. Magnetic properties

1968 ◽  
Vol 21 (6) ◽  
pp. 1517 ◽  
Author(s):  
den Bergen A van ◽  
KS Murray ◽  
BO West
Keyword(s):  
Magnetic Properties ◽  
Schiff Base ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Ferric Ion ◽  
Binuclear Complexes ◽  
Magnetic Susceptibilities ◽  
Mononuclear Complexes ◽  
Bulk Susceptibility ◽  
Spin Spin Coupling

The magnetic susceptibilities of iron(111) N-substituted salicylaldimine complexes of types Fe(sal-XR)3, Fe(sal-NR)2X, [Fe(salH-KR)2X]X, (X = Cl, Br), and [Fe(sal-NR)2]2O have been measured over the temperature range 90-300�K.? The mononuclear complexes exhibit normal high-spin (S = 5/2), Curie-Weiss behaviour. The binuclear oxygen-bridged complexes show antiferromagnetic behaviour and the results have been analysed using the spin-spin coupling mechanism. The exchange interaction is found to be independent of the nature of the N-substituent on the Schiff base. It appears that bulk susceptibility measurements alone cannot unambiguously specify the formal spin state of the ferric ion in these binuclear complexes.

A solid-state 31P NMR study of 1:1 silver–triphenylphosphine complexes — Interpretation of 1J(107,109Ag,31P) values,

2009 ◽  
Vol 87 (7) ◽  
pp. 1090-1101 ◽  
Author(s):  
Fu Chen ◽  
Se-Woung Oh ◽  
Roderick E. Wasylishen
Keyword(s):  
Solid State ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
P Values ◽  
X Ray Crystallography ◽  
Phosphine Complexes ◽  
Nmr Study ◽  
Fermi Contact ◽  
Spin Spin Coupling ◽  
Cp Mas Nmr

High-resolution solid-state 31P NMR spectroscopy was used to investigate a series of 1:1 silver–triphenylphosphine complexes, [Ph3PAgX]n, where X is a monovalent anion and n = 1, 2, 3, 4, or ∞. The 31P CP MAS NMR spectra reveal the number of distinct phosphorus sites in these complexes as well as the |1J(109Ag,31P)| values, which range from 401 ± 10 Hz (X = N3–) to 869 ± 10 Hz (X = SO3CF3–). The data obtained here and in earlier investigations indicate that |1J(109Ag,31P)| values for silver–tertiary phosphine complexes decrease as Ag–P bond lengths increase. This experimental conclusion is supported by DFT calculations, which also indicate that the Fermi-contact mechanism is the only important spin–spin coupling mechanism for 1J(109Ag,31P) in these complexes. In addition, the crystal structure of a silver–triphenylphosphine trifluoroacetate tetramer was determined using X-ray crystallography, and the structure of a silver–triphenylphosphine chloride tetramer was reinvestigated.

Analysis of the NMR Spin−Spin Coupling Mechanism Across a H−Bond:  Nature of the H-Bond in Proteins

2004 ◽  
Vol 108 (3) ◽  
pp. 1115-1129 ◽  
Author(s):  
Tell Tuttle ◽  
Jürgen Gräfenstein ◽  
Anan Wu ◽  
Elfi Kraka ◽  
Dieter Cremer
Keyword(s):  
Spin Coupling ◽  
Coupling Mechanism ◽  
Spin Spin Coupling

Long-range proton-fluorine spin-spin coupling. Further evidence for a 'direct' mechanism

1973 ◽  
Vol 26 (12) ◽  
pp. 2659 ◽  
Author(s):  
W Adcock ◽  
SQA Rizvi
Keyword(s):  
Long Range ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
Strong Support ◽  
Spin Coupling ◽  
Coupling Mechanism ◽  
Direct Mechanism ◽  
Spin Spin Coupling

A variable temperature p.m.r. study of outho- and peri-acetyl substituted fluoro-naphthalenes (including o-fluoroacetophenone) has been carried out. Further, 1-fluoro- 8-methylnaphthalene (previously unknown) has been synthesized and its p.m.r. spectra has been measured at various temperatures. The data, together with 19F substituent chemical shifts (SCS) for ortho-substituted cyanofluoronaphthalenes, provide further strong support for a through-space coupling mechanism (JMe,F).

Spin–spin coupling constants between side-chain and ring fluorine nuclei in some benzotrifluoride, benzal fluoride, and benzyl fluoride derivatives: coupling mechanisms

1979 ◽  
Vol 57 (7) ◽  
pp. 807-812 ◽  
Author(s):  
Ted Schaefer ◽  
Walter Niemczura ◽  
Chiu-Ming Wong ◽  
Kirk Marat
Keyword(s):  
Nmr Spectra ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Complete Analysis ◽  
Side Chain ◽  
Coupling Mechanism ◽  
Conformational Preferences ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Coupling Mechanisms

A complete analysis of the 1H and 19F nmr spectra of 2,5- and 3,4-difluorobenzotrifluoride, together with multiple resonance experiments, yields the signs and magnitudes of the long-range 19F,19F and 1H,19F spin–spin coupling constants. The coupling mechanisms are discussed. In particular, the coupling over six bonds, [Formula: see text], whose sign is interpretable in terms of a σ–π mechanism, is too large in magnitude when compared to [Formula: see text], and [Formula: see text] in the analogous compounds. These latter three couplings are consistent in sign and magnitude with what is known about hyperfine interaction constants. The magnitudes of [Formula: see text] are reported for 4-fluorobenzotrifluoride, 3-amino-4-fluorobenzotrifluoride, 3-nitro-4-fluorobenzotrifluoride, as are 6JpF,F values for p-fluorobenzal fluoride and p-fluorobenzyl fluoride. In contrast to 6JpH,CH and 6JpF,CH it seems unlikely that, unless its coupling mechanism becomes more precisely understood, 6JpF,CF will be a reliable indicator of conformational preferences.

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