Lanthanide Shift Reagents in Nuclear Magnetic Resonance Spectroscopy

I. INTRODUCTION

Three decades have elapsed since the first detection of nuclear magnetic resonance (NMR) effects in bulk matter. The intervening period has been rich in rewarding results as the relevant theory has been thought through, the experimental techniques developed, and the applications accumulated. Nevertheless, a review of the current "state of the art" shows that significant progress continues to be made on almost all fronts. Within the last few years new fields of application have been opened by the development of super-conducting solenoids,^1-3 by the introduction of various spin-decoupling techniques,^4,5 and by the method of pulse Fourier transform NMR spectroscopy.^6-9 As these innovations originate mainly from progress in instrumentation, acquisition of the techniques by individual laboratories involves the expenditure of considerable sums of money. A much less expensive, but nonetheless important, development in NMR spectroscopy has been the recent introduction of paramagnetic lanthanide complexes as "chemical shift reagents." The theoretical background, practical aspects, and applications of these reagents form the subject of this review.