Metalated 1,7-Diacetylide-BODIPY and Related Organic Chromophores: Synthesis, Structure, and Photophysics

Abstract

The readily accessed 1,7-dibrominated derivative of 2,3,5,6-tetramethyl-BODIPY is shown to be an effective precursor to a derivative appended with acetylide −C≡CH groups at these positions, through the intermediacy of the trimethylsilyl-protected compound (−C≡C–SiMe3). The acetylide functionality can in turn be metalated with dicobalt-hexacarbonyl clusters, or incorporated into 1,2,3-triazole rings through reaction with in situ generated propyl azide. The resulting new compounds have been structurally characterized by X-ray crystallography. Their electrochemical and optical spectroscopic properties are described and interpreted with the aid of time-dependent density functional theory (TD-DFT) calculations. The acetylide and the triazole derivative are intensely fluorescent in organic solvents at ambient temperature. Bis-N-methylation of the triazole gives a bis-triazolium salt that is soluble in water, while retaining a very high fluorescence quantum yield. On the other hand, the Co2(CO)6 appendages completely quench the fluorescence of the BODIPY moiety, likely through efficient intramolecular energy transfer, an interpretation supported by the spectral overlap of the absorption and emission of the respective units.