Second sphere coordination of phenols, anilines, and benzoic acids to the hexacyanocobaltate(III) anion

1983 ◽  
Vol 61 (7) ◽  
pp. 1524-1531 ◽  
Author(s):  
Donald R. Eaton ◽  
Richard J. Buist ◽  
Carol V. Rogerson
Keyword(s):  
Hydrogen Bond ◽  
Correlation Time ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Quadrupole Coupling Constant ◽  
Benzoic Acids ◽  
Coupling Constant ◽  
Line Broadening ◽  
Quadrupole Coupling ◽  
Hydrogen Bonded

Complexing between the hexacyanocobaltate(III) anion and ten substituted phenols, eight substituted anilines, and eight substituted benzoic acids has been studied in dimethyl sulfoxide solutions by means of 59Co nmr. For the phenols substantial changes in the chemical shifts and in the line widths are observed and are attributed to hydrogen bonding interactions. Effective equilibrium constants and chemical shifts for the hydrogen bonded species have been calculated. The equilibrium constants vary with the phenol substituent, being largest for electron withdrawing substituents and smallest for electron donating substituents. The chemical shifts are virtually independent of substituent. The data show that the lifetimes of the hydrogen bonded complexes are long compared to the rotational correlation time. The complex with para-nitrophenol has also been studied by measuring 1H and 13C spin–lattice relaxation times. These measurements allow the separation of the increase in 59Co line width due to increase in correlation time and that due to increase in quadrupole coupling constant. From the 13C measurements a value of the correlation time for the complex of 2.8 10−1 s is obtained together with a 59Co quadrupole coupling constant of 8.34 MHz. The equilibrium constants for complex formation with the anilines are small and only the products of the equilibrium constant and the chemical shift of the hydrogen bonded complex can be derived from the experimental data. The benzoic acids show evidence of dimerization in solution and this again prevents the calculation of absolute equilibrium constants. The data, however, do indicate that the ability to form hydrogen bond complexes does not vary dramatically with the acid strength of the hydrogen donor. With phenols and benzoic acids there is considerable line broadening on complex formation but with anilines only a small line broadening is observed. This is consistent with very short hydrogen bond lifetimes for the aniline complexes.

35Cl AND 37Cl MAGNETIC RESONANCE OF SIMPLE CHLORINE COMPOUNDS

1965 ◽  
Vol 43 (9) ◽  
pp. 2530-2534 ◽  
Author(s):  
Yasukazu Saito
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Quadrupole Coupling Constant ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Reference Compound ◽  
Excitation Energies ◽  
Structural Applications ◽  
Quadrupole Coupling ◽  
Magnetic Resonances

The nuclear magnetic resonances of 35Cl and 37Cl in a number of simple chlorine compounds were measured. Since both the paramagnetic contribution for chemical shift and the quadrupole coupling constant of the atom are determined by the same radial distribution of the electron, a linear relationship between the chemical shifts and the quadrupole coupling constants may be expected for compounds for which the electronic excitation energies are comparable. This was demonstrated for the series of chloro-substituted methanes. By graphical extrapolation the absolute chemical shift of the reference compound, NaCl aqueous solution, was obtained. The chemical shift of Cl− aq. ion can be interpreted as the sum of the diamagnetic shift of Cl− spherical ion and a paramagnetic shift resulting from its hydration. The experimental and theoretical values of the paramagnetic chemical shift of the Cl2 molecule were −2.06 × 10−3 and −2.17 × 10−3, respectively. Paramagnetic chemical shifts and line widths of resonance spectra of simple chlorine compounds are discussed, as well as the feasibility of high-resolution chlorine resonances for structural applications.

Conformational Analysis of Chloromethylenimine and its Hydrogen-Bonded Dimers with Water from the Study of Nuclear Quadrupole Interactions

1996 ◽  
Vol 51 (5-6) ◽  
pp. 534-536 ◽  
Author(s):  
N. Sathyan ◽  
V. Santhanam ◽  
J. Sobhanadri
Keyword(s):  
Proton Affinity ◽  
Quadrupole Coupling Constant ◽  
Basis Set ◽  
Coupling Constant ◽  
Quadrupole Interactions ◽  
Nuclear Quadrupole Interactions ◽  
Nuclear Quadrupole Coupling Constant ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Hydrogen Bonded

Abstract A molecular conformation study on N-Chloromethylenimine and its 1:1 dimeric form with water has been carried out using the ab-initio method at 6-31 G and 6-31 G* basis set. We consider the two most stable conformers of the N-chloromethylenimine -water binary mixture involving double hydrogen bonds. In all cases the proton affinity has been calculated. Each system considered in this work has the nuclear quadrupole interactions of the nitrogen and chlorine resonant nuclei which have been calculated and compared. It is found that the nuclear quadrupole coupling constant for the nitrogen nucleus increases in the hydrogen bonded complexes and decreases for the chlorine nucleus compared to the monomeric values. The influence of proton affinity is reflected in the nuclear quadrupole coupling constant.

AB INITIO CALCULATIONS OF 14N NQR PARAMETERS AND 13C, 1H, AND 15N CHEMICAL SHIFTS INCLUDING A COMPARISON WITH EXPERIMENTAL NMR DATA FOR CYCLOTRISAZOBENZENE

2009 ◽  
Vol 08 (04) ◽  
pp. 647-656 ◽  
Author(s):  
NASSER ZAMAND ◽  
ALI R. ALIAKBAR ◽  
NASSER L. HADIPOUR
Keyword(s):  
Structural Changes ◽  
Chemical Shifts ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Electron Pairs ◽  
Nuclear Quadrupole Coupling Constant ◽  
Quadrupole Coupling ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole ◽  
Experimental Values

Nuclear quadrupole coupling constant, χ, and asymmetry parameter, η, of 14 N nucleus and 13 C , 1 H , and 15 N chemical shifts for cyclotrisazobenzene at the level of B3LYP and MP2 methods have been studied using the Gaussian 98 suite of programs. Also, nuclear quadrupole resonance (NQR) frequencies (ν0, ν+, ν-) for 14 N have been calculated, thoroughly. The optimized structure of the compound was very similar to that given by the X-ray crystallographic data. The electric field gradient (EFG) calculation verified that the N = N bonds are highly localized in this molecule; therefore, electron-pairs of the nitrogen atoms remain nonbonding. The comparison of the calculated chemical shifts with the experimental values for cyclotrisazobenzene shows no significant structural changes in solution.

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