Syntheses of boronic-acid-appended metalloporphyrins as potential colorimetric sensors for sugars and carbohydrates

Boronic-acid-based dyes have been widely studied in the past decade as potential sensors for sugars and carbohydrates, owing to the strong interaction of boronic acid and diols. In this work, two boronic-acid-appended metalloporphyrins were synthesized by new routes and tested as potential sugar and carbohydrate sensors. Boronic acid substituents were attached either to a βpyrrolic position ((2-dihydroxylboryl-5,10,15,20-tetraphenylporphyrinato)zinc(II), 1) or to the mesoposition ((10-dihydroxylboryl-5,15-diphenylporphyrinato)zinc(II), 2) of the porphyrin core. These complexes were tested as potential carbohydrate sensors; unfortunately, no UV-vis or fluorescence spectra changes were observed with the addition of glucose or fructose. Molecular orbital calculations confirm little electronic conjugation between the porphyrin π-system and the boronic acid substituents in either pyrrolic or meso-positions. Copyright © 2005 Society of Porphyrins & Phthalocyanines.