The Added Value of Solid‐State Pb NMR Spectroscopy to Understand the 3D Structures of Pb Amino Acid Complexes

Abstract

Abstract Single‐crystal X‐ray diffraction and solid‐state 207 Pb NMR spectroscopic experiments have been conducted on four lead amino acid complexes with nitrato or perchlorato counterions, namely neutral isoleucine ( 1 ), deprotonated leucine ( 2 ), monodeprotonated aspartic acid ( 3 ), and neutral valine ( 4 ). The crystal structures reveal that the Pb II ions are preferably coordinated by oxygen atoms and that the amine group of the amino acids is coordinated only in the case of leucine. The results of the solid‐state NMR spectroscopic experiments are compared to the 3D structures obtained from single‐crystal X‐ray data. The NMR spectroscopic experiments show one, two, one, and four lead sites for the Hile, leu – , Hasp – , and Hval complexes, respectively, in agreement with crystal structures. The application of this method towards the characterization of new Pb compounds, for which no 3D structure is known, is discussed and illustrated with an example where a mechanical mixture of two lead complexes is characterized successfully. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)