Synthesis and Photophysical Properties of Naphtho[b]- and Indeno[b]-fused BODIPYs

Abstract A new synthetic method to construct [b]-fused BODIPY derivatives through PtCl2-catalyzed cycloisomerization reaction of peripherally phenylacetylene substituted BODIPYs is reported. Electron donating methoxy group facilitate both the 6-endo and 5-exo cyclization procedure to produce naphtho[b]- and indeno[b]-fused BODIPYs in one pot reaction. Naphtho[b]-fused BODIPY exhibits redshifted absorption and emission (591 nm/621 nm) with higher quantum yield (0.56 in DCM), while indeno[b]-fused BODIPY shows very low quantum yield (0.01 in DCM) with shorter absorption and emission wavelength (571 nm/600 nm) and stronger absorption intensity. Quantum-chemical calculation revealed the antiaromatic nature of cyclopentadienyl ring in indeno[b]-fused BODIPY, which accounts for its inferior photophyscal properties.