1. Méthodologie RMN (UMR CNRS-UHP 7565), Nancy-Université, Faculté des Sciences, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France, and Department of Structure Analysis, Institute of Molecular Chemistry AV CR, v.v.i., Heyrovskeho nam. 2, 162 06 Praha-6, Czech Republic