The synthesis of ligands (2,9-disubstituted phenanthrolines) bearing one or two acylaminopyridine binding sites, compounds 1 and 2 respectively, is described. Each ligand can assemble on a Cu(I) template, forming two different receptors for dicarboxylic acids, Cu(l)2+BF4-and Cu(2)2+Bp4-. These orange Cu(I) complexes are shown to bind (Xa > 10* 1234 567M-1) to a variety of dicarboxylic acids in chloroform, with a slight preference for the Cs-dicarboxylic acids, glutaric and V-CBz-glutamic acids, over shorter and longer substrates. Complexation is analyzed both by NMR chemical shift changes and UV-visible absorption changes. The data indicate formation of 1:1 complexes for Cu(l)2+BF4~a nd 2:1 complexes for Cu(2)2+Bp4-, with the dicarboxylic acid substrate hydrogen bonding simultaneously to an acylaminopyridine binding site on each ligand. For Cu(2)2+BF4-, the complexation event results in large shifts in the visible absorption bands and a color change from orange to red. The change in the visible absorbance, and therefore the chromogenicity, was found to be substrate dependent. The chromogenic effect is explained by a conformational change in the receptors resulting from hydrogen bond formation with the substrate.
[structure: see text] Based on the high affinity of phenanthroline-strapped porphyrins for imidazoles, building blocks for self-assembled, linear porphyrin architectures have been designed. Their synthesis is reported, and the assembly principle is illustrated by the formation of the shortest possible scaffold. Only one type of assembly is observed, and the stepwise energy transfer from the boron dipyrrylmethane (BODIPY) input to the free base output is highly efficient.
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