Molecular recognition and sensing by macrocycles: Synthesis and applications of macrocycles with convergent functionalities

A novel class of macrocycles, the cyclic trimers of 3′-amino-3-biphenylcarboxylic acid, was designed and synthesized. The macrocycle has a unique structure characterized by the rigid disposition of hydrogen bonding groups in the interior of a macrocyclic scaffold. This convergent projection of dipoles enables the macrocycle to bind anions with size and shape selectivity and different modes of complexation were observed depending on the anion properties and solvent polarity.; This novel macrocycle was used as a building block in the formation of fluorescence sensors. A macrocycle containing an aminocoumarin fluorophore showed two different fluorescence emission bands on binding with certain anions. Proton transfer from the fluorophore excited state occurred depending on the basicity of the bound anion and this new pathway makes more selective and sensitive anion sensing possible.; Modified macrocycles containing two or three heteroaromatic rings were prepared. Unlike other macrocycles widely used for molecular recognition studies, the modular stepwise synthesis of the cyclic trimer of 3′-amino-3-biphenylcarboxylic acid makes the modifications inside and outside of the central cavity relatively straightforward.