NMR study of dendrimer structures using paramagnetic cobalt(II) as a probe

Cobalt(II) has been utilized as an external paramagnetic H-1 NMR probe for the study of the structure of dendrimers that possess specifically located metal recognition sites. The isotropically shifted LII NMR signals of the C o(II) complexes of two 2,6-diamidopyridine-containing dendrimers have been fully assigned by means of 1D and 2D NMR techniques, including NOE differen ce, EXSY, COSY, and TOCSY. T-1 values of the isotropically shifted signals were used to calculate metal-proton distances to build a molecular model of the internal structure of the dendrimers. The presence of sizable cavities within the dendrimers was observed, including a loosely packed conformatio n for the 2,6-diamidopyridine moiety to bind to potential guest molecules.