Synthesis and studies of covalently linked pyrrolyl bridged fluorescent dimers

Abstract

A series of stable fluorescent compounds namely the pyrrolyl bridged bis-(BODIPY) and bis-(22-oxacorrole) dimers were synthesized using pyrrolyl bridged bis-(dipyrromethane) as key precursor. The pyrrolyl bridged bis-(dipyrromethane) was synthesized in two steps by using commercially available compounds and used for the synthesis of pyrrolyl bridged bis-(BODIPY). The chloro groups present at the bridging pyrrole ring of bis-(BODIPY) dimer were replaced with aryl groups by the treatment of two different aryl boronic acids under Suzuki Coupling conditions. In order to show a further use of the pyrrole bridged bis-(dipyrromethane) precursor, it was condensed with 16-oxatripyrrane which rendered the pyrrolyl bridged bis-(22-oxacorrole) dimer as a green fluorescent compound in 8% yield. The dimers were thoroughly characterized by NMR and mass and the properties were investigated by absorption, fluorescence, electrochemical and DFT/TD-DFT studies. DFT studies showed that the bis-(BODIPY) and bis-(22-oxacorrole) dimers were highly symmetric and TD-DFT studies were in agreement with the experimental absorption and redox properties.