Conjugated, trans-Spanning Ligands as Models for Multivalent p-Phenyleneethynylenes


A conjugated, pyridine-containing, phenylethynyl ligand that forms complexes with AgI and PdII has been developed. NMR titration studies with PdII reveal a stoichiometric binding of the ligand to the metal atom, while similar studies with AgI reveal a binding that is dynamic on the NMR timescale. Analysis of the NMR spectroscopic data by Job's plot analysis and non-linear curve fitting of a titration curve reveals a 1:1 binding ratio of ligand/silver cation and an association constant of Ka = 53 M"“1. X-ray crystal structures of the ligand"“metal complexes suggest ample room for the nearly barrierless rotation of the unsubstituted central benzene ring of the para-phenylethynyl chain. Subtle electronic differences in substituted systems provide some evidence of impaired rotation.


Chemistry and Biochemistry

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The Journal of organic chemistry