Bis-porphyrin tweezers: rigid or flexible linkers for better adjustment of the cavity to bidentate bases of various size

Abstract

We report herein the binding studies of three bis-porphyrinic tweezers bearing nucleosidic linkers and a bis-porphyrinic dipeptide with two bidentate bases of different size, DABCO and 4,4' -bipyridine. In the nucleosidic series, the nucleoside confers, for two dimers out of three, sufficient preorganization to the dimers to enhance the association constants, documenting the fact that rigid dimers are not necessary for preorganization, and opening up new routes to the faster synthesis of flexible tweezers capable of complexing guests with a high association constant. Comparison of these results with those obtained for rigid tweezers shows a better efficiency of the flexible nucleosidic dimers. We thus document the fact that the choice of rigid spacers is not the only way to pre-organize bis-porphyrins, and that some well-chosen nucleosidic linkers offer an interesting option for the synthesis of such devices.