Paramagnetic Solute Research Articles

Dynamics of interspecies hydrogen bonding of a fluorinated alcohol and a nitroxide free radical

The combined use of (1) the magnetic field dependence of solvent nuclear relaxation times induced by paramagnetic solutes and (2) the dynamic nuclear polarization of the same solvent nuclei is reported in a study of the dynamics of interactions between trifluoroethanol and 4-oxo-2,2,6,6-tetramethyl piperidino-oxy free radical. The –OH proton behavior is dominated by dipolar coupling with the spin-label unpaired electron that is characterized by rotational diffusion of the complex with a correlation time of 5×10−11 s and an interaction distance of 2.6 Å. The interaction with the –CH2 protons and –CF3 fluorine nuclei is weaker, dominated by dipolar coupling with the free radical, and characterized by a shorter correlation time.

Evaluation of a cross-correlation method for the determination of nuclear spin-lattice relaxation times of solvents containing paramagnetic solutes

An analysis is given of an Overhauser experiment in which the microwave power is applied as a square wave in time: in response to this square wave the observed NMR signal relaxes toward modified equilibrium levels. It is shown how T 1 of the relaxing nuclei may be determined from the cross-correlation function between the impressed microwave power and the observed NMR signal intensity. Results are given for solutions of 2,2,6,6-tetramethyl-4-oxopiperidine-l-oxyl in water.

ESR linewidth in oriented solvents with two-angle-dependent distribution function

The linewidth theory for partially oriented molecules is extended to paramagnetic solutes subjected to a two-angle-dependent orienting potential V(β,γ). A perturbation approach is used to solve the diffusion equation and to calculate the zero-frequency spectral densities.

Investigation of the hydrophobic interaction between tert-butyl alcohol and paramagnetic solutes in aqueous solutions by proton nuclear magnetic resonance relaxation

Investigation of the hydrophobic interaction between tert-butyl alcohol and paramagnetic solutes in aqueous solutions by proton nuclear magnetic resonance relaxation

Electron resonance in the smectic mesophase

The smectic mesophase obtained by cooling the nematic mesophase of 4,4′-di- n-heptyloxyazoxyphenzene in a magnetic field is shown to order a paramagnetic solute less than the nematic phase. When the smectic mesophase is produced in this way the direction of the ordering potential is found to be uniform over the sample and fixed with respect to the sample tube.

Mechanism of antiferromagnetism in dilute alloys

A mechanism for the antiferromagnetic ordering of a dilute paramagnetic solute in a metal is proposed and discussed in relation to the phenomena that occur in copper-manganese alloys. Long-range antiferromagnetic order results from a static spin-density wave in the electron gas of the metal. This new state of the gas is dynamically self-sustaining as a result of the exchange potentials arising from the spin-density distribution. The paramagnetic solute atoms are then oriented by their exchange interaction with the spin-density wave. The resulting interaction energy more than compensates the increase in energy associated with the formation of the spin-density wave. The theory predicts correctly the magnitude and concentration-dependence of the critical temperature, the anomalous low-temperature specific heat and the anomalous electrical and magnetic properties of the alloys.

Mechanism of Antiferromagnetism in Dilute Alloys

Abstract A mechanism for the antiferromagnetic ordering of a dilute paramagnetic solute in a metal is proposed and discussed in relation to the phenomena that occur in copper-manganese alloys. Long-range antiferromagnetic order results from a static spin-density wave in the electron gas of the metal. This new state of the gas is dynamically self-sustaining as a result of the exchange potentials arising from the spin-density distribution. The paramagnetic solute atoms are then oriented by their exchange interaction with the spin-density wave. The resulting interaction energy more than compensates the increase in energy associated with the formation of the spin-density wave. The theory predicts correctly the magnitude and concentration-dependence of the critical temperature, the anomalous low-temperature specific heat and the anomalous electrical and magnetic properties of the alloys.

Magnetometric Titration: a New Method of Chemical Analysis

IT is well known that the addition of paramagnetic solutes to water brings about a marked reduction in the nuclear spin-lattice relaxation time of solvent protons1, the inverse of the relaxation time being linearly related to solute concentration according to the equation: where T 1 and T 0 are spin-lattice relaxation times in the presence and absence of added solute, respectively; α is a proportionality constant; μN is a parameter expressing the effectiveness of a particular solute in this phenomenon, sometimes called the ‘effective’ paramagnetic moment of the solute; C is the concentration of the solute. In the case of solutions of paramagnetic complex ions, the magnitude of the effect (that is, the value of μN) depends on the nature of the co-ordinated groups2. We find that the phenomenon enables the replacement of one ligand by another in solution to be followed with sufficient precision to form the basis for a method of determining the concentration of metal ions, and it is now suggested that this method of analysis should be widely applicable in cases where the addition of a complexing agent to the solution of a paramagnetic ion in solution causes the formation of a new complex ion of different μN and of high stability in solution. The analyses can conveniently be carried out by use of a low-resolution nuclear magnetic-resonance spectrometer.

Nuclear Spin Relaxation Studies in Dilute Sodium-Liquid Ammonia Solutions

The nuclear spin relaxation times of the protons in dilute solutions of sodium in liquid ammonia have been measured at 30 Mc/sec over the room temperature-dry ice range. The data can be interpreted on the basis of an associative equilibrium existing between paramagnetic and diamagnetic solute species. This is in agreement with the results of the conventional magnetic susceptibility measurements. The paramagnetic component of the solutions seems to be about one-tenth as effective as a cupric ion in inducing nuclear relaxation.