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.

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

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).

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.

Temperature and Solvent Dependence of 13C—H Spin-Spin Coupling Constant JCH in Ethyl Formate

1968 ◽  
Vol 23 (12) ◽  
pp. 2094-2097 ◽  
Author(s):  
Erkki Rahkamaa ◽  
Jukka Jokisaari
Keyword(s):  
Hydrogen Bonding ◽  
Ethyl Formate ◽  
Spin Coupling ◽  
Intermolecular Hydrogen Bonding ◽  
Formyl Group ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Solvent Dependence ◽  
Pmr Spectra ◽  
Spin Spin Coupling

PMR spectra of pure ethyl formate and its solutions in carbon tetrachloride, carbon disulfide and acetone indicate that both the directly bonded 13C—H coupling constant and the chemical shift of the formyl group vary with temperature, solvent and concentration. Some aspects of the temperature and solvent dependence of JCH and δ can be related to the intermolecular hydrogen bonding involving the formyl proton. The possibility of the existence of other factors must however not be forgotten.

A proton magnetic resonance estimate of the extent of intramolucular hydrogen bonding in derivatives of 2-trifluoromethyl phenol. Solvent effects

1976 ◽  
Vol 54 (14) ◽  
pp. 2243-2248 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Free Energy ◽  
Hydrogen Bonding ◽  
Vapor Phase ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Group ◽  
Spin Coupling Constants ◽  
Hydroxyl Protons ◽  
Spin Spin Coupling ◽  
Derivatives Of

The long-range spin–spin coupling constants between hydroxyl protons and ring protons or fluorine nuclei are used to establish the conformer populations in iodine and brornine derivatives of 2-trifluoromethylphenol in C6H12, CCl4, and C6D6 solutions. The sequence Cl, [Formula: see text] is established for the so-called hydrogen bonding preferences of the hydroxyl group in 2,4,6-trisubstituted phenols, the corresponding free energy sequence being −ΔG = 1690, 1690 > 1300 > 1230 > 0 ± 200 cal/mol at 32 °C in CCl4 solution. An indirect estimate of the free energy differences in the vapor phase suggests the sequence −ΔG = 2800, 2800 > 2400 > 2300 > 1100 ± 300 cal/mol; the latter value meaning that the hydroxyl group in 4-bromo-2-trifluoromethylphenol prefers the CF3 group by this amount in the vapor phase. Benzene interacts preferentially with the OH group in this compound to the extent of 1300 cal/mol (ΔG), referenced to the vapor phase.

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