Walter J. Freeman

Platinum-195 NMR using Fourier transform techniques. The PtCl42− ion

Abstract Pt-195 Fourier transform NMR spectra of some salts of platinum have been measured. The technique is shown to be readily applicable to measuring platinum spectra and yields chemical information not readily available using indirect methods of observation. The solvent dependence of the chemical shift of the PtCl 4 2− ion is suggested to be related to an interaction of solvent with the solute.

Rotating frame nuclear relaxation of PBr3: Off-resonance studies by fourier transform NMR

Abstract The theory for off resonance measurements of the nuclear spin-lattice relaxation time in the rotating coordinate frame (T1ϱ) is developed to facilitate measurements of this parameter by Fourier transform (FT) NMR. Measurements on PBr3 are used to test the theory, but the technique is developed so as to apply to multiline spectra suitable for FT-NMR study. Methods of interpreting data and applications are discussed.

Automated nonselective measurement of T1ρ by Fourier transform NMR

A simple, computer automated method for measuring rotating frame relaxation times (T1ρ) for many line spectra on modified commercial NMR spectrometers is discussed. Sources of error and critical instrumental parameters are identified. Adjustment of the various parameters of the pulsed rf system is more critical than for T1 but perhaps less so than for T2 measurements.

Nuclear magnetic relaxation of 31P in phosphorous halides

31P NMR spin–lattice relaxation time measurements in the laboratory frame, T1, and in the rotating coordinate frame, T1ρ, are reported for an equimolar mixture of PBr3 and PCl3. Relaxation times were measured as a function of temperature. T1ρ was measured also as a function of offset and lock‐field strength. The lock‐field dependent T1ρ technique is shown to be inadequate for exact determinations of scalar spin–spin coupling constants. We report for all four molecular species PBr3, PBr2Cl, PBrCl2, and PCl3 the following quantities: activation energies and frequency factors for chemical exchange and molecular reorientation and spin–lattice relaxation times for the bromines and chlorines. These quantities are obtained from the temperature dependent T1ρ measurements, which are shown to be suited for the study of chemical exchange processes when the exchange rates are in the order of 103–105 s−1. Using known values for quadrupolar coupling constants, we derive the temperature dependence of the reorientation c...