Pb-207-H-1 two-dimensional NMR spectroscopy: A useful new tool for probinglead(II) coordination chemistry

Despite the fact that lead poisoning is the most common disease of environm ental origin in the United States, the spectroscopic properties of aqueous Pb(II) coordination compounds have not been extensively investigated. Spect roscopic techniques that can be used to probe the fundamental coordination chemistry of Pb(TI) will aid in both the development of water-soluble ligan ds that bind lead both tightly and selectively and the characterization of potential biological targets. Here, we report the preparation and character ization of a series of Pb(II) complexes of amido derivatives of EDTA. The P b-207, chemical shift observed in these complexes (2441, 2189, and 1764 ppm for [Pb(EDTA)](2-) Pb(EDTA-N-2), and [Pb(EDTA-N-4)](2+), respectively) pro vides an extremely sensitive measure of the local environment and the charg e on each complex. These shifts help to map out the lead chemical measure o f the local environment shift range that can be expected for biologically r elevant sites. In addition, we report the first two-dimensional Pb-207-H-1 heteronuclear multiple-quantum correlation (HMQC) nuclear magnetic resonanc e spectra and demonstrate that this experiment can provide useful informati on about the lead coordination environment in aqueous Pb(II) complexes. Bec ause this technique allows Pb-207-H-1 couplings through three bonds to;be i dentified readily, Pb-207-H-1 NMR spectroscopy should prove useful for the investigation of Pb(II) in more complex systems (e.g., biological and envir onmental samples).