Synthesis and photophysical properties of near infra-red absorbing BODIPy derivatives and their nanoaggregates

Abstract

A facile synthesis of 1,3,5,7-tetraaryl (thienyl and pyrenyl) substituted BODIPy derivatives from tetramethyl BODIPy and aryl aldehydes via one-pot Knoevenagel reaction conditions has been carried out to yield extensively conjugated BODIPy (1,2). Drastic bathochromic shift of more than 200 nm was observed in absorption (∼up to 700 nm) and emission (up to ∼740 nm) maxima of 1,2 as compared to classical BODIPy (∼500 nm). Nano-aggregates of 1,2 were prepared by re-precipitation method in aqueous medium and are characterized by absorption, emission, transient lifetime, DLS and SEM measurements. These studies revealed the aggregation formation through BODIPy core which is further strengthen by peripheral aryl substituents. Furthermore singlet oxygen production ability of 1,2 and their nano-aggregates were studied. Importantly, the nano-aggregates reveal superior singlet oxygen production ability in the aqueous phase as compared to their monomers in the biologically advantageous near-IR region.