Spin Spin Interactions in Polynuclear Nickel(II) Complexes. a Magnetic and Structural Study of Binuclear Nickel(II) Complexes of Enolic 1,3,5-Triketonates

1986 ◽  
Vol 39 (8) ◽  
pp. 1249 ◽  
Author(s):  
PDW Boyd ◽  
KS Lee ◽  
M Zvagulis
Keyword(s):  
Marked Decrease ◽  
Nickel Complexes ◽  
Spin Coupling ◽  
Spin Interaction ◽  
Binuclear Copper ◽  
X Ray ◽  
Spin Interactions ◽  
Spin Spin Coupling ◽  
Antiferromagnetic Spin ◽  
Oxygen Bond

The bulk magnetic susceptibilities of the binuclear nickel(II) complexes of the 1,3,5-triketonates from diethyl (2-oxocyclopentane- 1,3-diyl) bisglyoxylate (H2ecg) (1) and diethyl 2,4,6-trioxoheptanedioate (H2decg) (2) have been measured over the temperature range 6-300 K. Antiferromagnetic spin-spin coupling is observed in each case with Neel temperatures in the range 45-65 K. The X-ray crystal structure of [Ni( ecg )( py )2]2.( py ) has been solved. The complex crystallizes with one pyridine of solvation in the space group Pī [a 10.507(1), b 13.384(1), c 9.992(1) Ǻ, α 103.004(9), β 115.867(9), β 86.857(10)°, Z = 1]. The molecule is binuclear with two coplanar triketonate dianions bridging the two six-coordinate nickel atoms through a di-μ-oxo linkage [Ni-Ob-Ni angle 102.0(1)°]. Two pyridine molecules and four triketonate oxygen atoms are bound to each nickel atoms. Magnetostructural correlations are presented in comparison with binuclear copper(II) 1,3,5-triketonates. The marked decrease in spin-spin interaction in the nickel complexes is attributed to increasing metal-bridging oxygen bond lengths that decrease the efficacy of the σ antiferromagnetic pathway xy||Ob||xy and contributions from the ferromagnetic xy||Ob||z2 pathway.

Molecular Conformation of 4-Thiouridine in Aqueous Solution

1971 ◽  
Vol 49 (14) ◽  
pp. 2449-2452 ◽  
Author(s):  
F. E. Hruska ◽  
K. K. Ogilvie ◽  
A. A. Smith ◽  
H. Wayborn
Keyword(s):  
Aqueous Solution ◽  
Long Range ◽  
Crystalline State ◽  
Molecular Conformation ◽  
Spin Coupling ◽  
Pyrimidine Nucleoside ◽  
Coupling Interaction ◽  
X Ray ◽  
Anti Conformation ◽  
Spin Spin Coupling

β-4-Thiouridine is a component of several tRNA molecules. A recent X-ray study has shown that this pyrimidine nucleoside favors the syn conformation in the crystalline state. The 100 and 220 MHz p.m.r. data and a comparison with those of uridine are presented here. A long-range five-bond spin–spin coupling interaction between the H-5 and -1′ hydrogens is noted. The results are consistent with an anti conformation for 4-thiouridine in an aqueous solution.

H-Bonding on spin centres enhances spin–spin coupling for organic diradicals

2020 ◽  
Vol 8 (10) ◽  
pp. 3402-3408 ◽  
Author(s):  
Francis Kirby B. Burnea ◽  
Yeonsig Nam ◽  
Jin Yong Lee
Keyword(s):  
Hydrogen Bonding ◽  
Spin Coupling ◽  
Hydrogen Bonding Interactions ◽  
Spin Interactions ◽  
Spin Spin Coupling

Intramolecular ferromagnetic spin–spin interactions in a nitroxide-based organic diradical is enhanced by hydrogen-bonding interactions through the spin centers.

scholarly journals One and Multiple Bonds Interatomic Spin-Spin Coupling inη6-Cymene Ru(II) of 3,5-Dimethyl-, 3,5-Dicarboxylic-, and 5-Phenyl-pyrazole Derivatives

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Adebayo A. Adeniyi ◽  
Peter A. Ajibade
Keyword(s):  
Ruthenium Complexes ◽  
Spin Coupling ◽  
Multiple Bonds ◽  
Interatomic Distances ◽  
Spin Interactions ◽  
Fermi Contact ◽  
Shielding Tensor ◽  
Spin Spin Coupling ◽  
Hydrolysis Of ◽  
Derivatives Of

The changes in the interatomic distances and the corresponding spin-spin coupling as a result of the hydrolysis of the ruthenium complexes and the effects of different derivatives of the pyrazole ligands and the substituents methyl, carboxylic, and phenyl on the pyrazole rings were studied. A good agreement was obtained between the experimental and the theoretical proton NMR. Significant changes are observed in the isotropic and anisotropic shielding tensor of the atoms and related spin-spin coupling of their bonds due to hydrolysis of the complexes. This observation gives more insight into the known mechanism of activation of the ruthenium complexes by hydrolysis. There are no direct effects of interatomic distances on many of the computed spin-spin couplings with the exception of1J(Ru-N) which shows significant changes especially within the pair of1J(Ru-N) in the complexes with two nitrogen atoms of the bis-pyrazole moiety. The magnitude of interatomic spin-spin coupling of the Ru-X follows the order of Ru-Cl > Ru-N > Ru-C > Ru-O. The Ramsey term Fermi contact (FC) has the most significant contribution in most of the computed spin-spin interactions except in1J(Ru-Cl) and1J(N-N⁎) which are predominantly defined by the contribution from the paramagnetic spin orbit (PSO).

X-ray diffraction and solid-state 119Sn CP-MAS NMR studies of some triaryltin(IV) chlorides

2003 ◽  
Vol 81 (11) ◽  
pp. 1187-1195 ◽  
Author(s):  
Jordan M Geller ◽  
Ian S Butler ◽  
Denis FR Gilson ◽  
Frederick G Morin ◽  
Ivor Wharf ◽  
...  
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Spin Coupling ◽  
Magic Angle ◽  
X Ray ◽  
Tin Chloride ◽  
Angle Spinning ◽  
Spin Spin Coupling

The solid-state 119Sn cross-polarization (CP) magic angle spinning (MAS) NMR spectra of a series of triaryltin chlorides of the form Ar3SnCl have been acquired. The indirect spin-spin coupling constants (J(119Sn-35Cl)), quadrupolar-dipolar shifts (d(119Sn-35Cl)), and the 119Sn chemical shift tensors were extracted. For the spectrum of triphenyltin chloride (I) the validity of the first-order perturbation approximation was tested by comparing results of both the perturbation and cubic-equation approaches and a variable-temperature NMR study undertaken to investigate the influence of the previously reported molecular motion in the solid. The X-ray crystal structures of the tris(o-tolyl)tin chloride (II) and tris(p-tolyl)tin chloride (IV) complexes have been examined. They belong to the monoclinic and triclinic space groups P21/n and P[Formula: see text], respectively, which are different from the previously reported tris(m-tolyl)tin chloride (III) complex, which crystallizes in the space group R3 and has threefold molecular symmetry. The structures and NMR properties of the complexes with meta-substituents are quite different from those with ortho- or para-substituents having axially symmetric shift tensors with small spans and larger J values.Key words: aryltin chlorides, magic angle spinning NMR, tin-chlorine spin-spin coupling, 119Sn chemical shift tensor, crystal structure.

Polyhydroxy biphenyl ethers from the brown alga Cystophora congesta

1982 ◽  
Vol 35 (3) ◽  
pp. 649 ◽  
Author(s):  
RP Gregson ◽  
JJ Daly
Keyword(s):  
Aqueous Extract ◽  
Brown Alga ◽  
Chemical Shifts ◽  
Spin Coupling ◽  
X Ray ◽  
Spin Spin Coupling

Two new phloroglucinol polymers have been isolated from the aqueous extract of the brown alga Cystophora congesta. They are the linear trimer 2,2',4,6,6'-pentahydroxy-1'-(3,5-dihydroxyphenoxy)- biphenyl ether (1)* and the isomeric angular trimer 3,4',5,6'- or 3,3',5,5'-tetrahydroxy-2'-(3,4,5-tri-hydroxyphenoxy)biphenyl ether which was characterized as its heptaacetoxy derivative (4). Structures were elucidated principally from an analysis of 13C n.m.r. chemical shifts and 13C-1H spin-spin coupling data. X-ray analysis was performed on the heptaacetoxy derivative of (1) to distinguish it from a regio-isomer (3).

scholarly journals Probing interactions through space using spin–spin coupling

2014 ◽  
Vol 43 (17) ◽  
pp. 6548-6560 ◽  
Author(s):  
Martin W. Stanford ◽  
Fergus R. Knight ◽  
Kasun S. Athukorala Arachchige ◽  
Paula Sanz Camacho ◽  
Sharon E. Ashbrook ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Solid State Nmr ◽  
Spin Coupling ◽  
X Ray ◽  
Solid State Nmr Spectroscopy ◽  
X Ray Crystallography ◽  
B3lyp Calculations ◽  
Spin Spin Coupling

A series of eight 5-(TeAr)-6-(SePh)acenaphthenes (Ar = aryl) were prepared and structurally characterised by X-ray crystallography, solution and solid-state NMR spectroscopy and DFT/B3LYP calculations.

Binuclear and mononuclear nickel(II) and zinc(II) complexes of the tetradentate ligand 1,4-di(2′-pyridyl)aminophthalazine

1980 ◽  
Vol 58 (3) ◽  
pp. 221-228 ◽  
Author(s):  
James Alfred Doull ◽  
Laurence Kenneth Thompson
Keyword(s):  
Nickel Complexes ◽  
Zinc Complexes ◽  
Spin Coupling ◽  
Binuclear Complexes ◽  
Antiferromagnetic Exchange ◽  
Tetradentate Ligand ◽  
Metal Ratio ◽  
Spin Spin Coupling ◽  
Hydroxy Groups

Previous studies with the title ligand, PAP, have shown a predominance of binuclear complexes with cobalt and copper in which the ligand-to-metal ratio is 1:2. The nickel complexes produced are more varied in composition; e.g., 1:2 binuclear systems [PAPNi2X(OH)(H2O)4]X2 (X = Cl, Br); 1:1 binuclear systems [PAP2Ni2(H2O)4]X4 (X = Cl, Br), [PAP2Ni2(NCS)3]NCS, [PAP2Ni2(OH)I2]I•2H2O, [PAP2Ni2(OH)(H2O)2]X3 (X = ClO4, BF4, I); and 2:1 mononuclear systems [(PAPH)2Ni(H2O)2]X4 (X = I, BF4). Zinc forms both mononuclear, [PAPZnX2]•H2O (X = Br, I), and a 1:1 binuclear system, [PAP2Zn2Cl4]. Triple bridges are suggested between the nickel atoms in all binuclear systems involving bridging hydroxy groups. Weak antiferromagnetic exchange is observed (−J < 10 cm−1) in two binuclear nickel complexes, which is enhanced in the presence of a hydroxy bridge. Spin–spin coupling is assumed to occur via a superexchange mechanism. In all cases nickel appears to be six-coordinate while for the zinc complexes both four- and six-coordination are observed.

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