Aza-BOIMPYs: A Tetrazole Auxochrome for Highly Red-Emissive Dipyrromethene-Based Fluorophores.

A structural derivative of the recently designed BOIMPY motif is introduced; this derivative engages a meso tetrazole moiety and a dipyrromethene scaffold in a twofold BF2 -coordination scheme. A one-pot synthesis allows the isolation of unusual dipyrro-perazafulvene precursors and subsequent access to nonfluorescent mono-BF2 and fluorescent bis-BF2 species. The novel fluorophore, denoted Aza-BOIMPY, is highly emissive (ΦF up to 0.82), structurally compact, and provides useful inherent polarity. Absorption and emission events focus at roughly 600 nm with exceptionally small Stokes shifts (209 cm-1 ) and high attenuation coefficients (up to 120 000 m-1  cm-1 ). X-ray crystallographic and computational investigations provide insights into geometrical and electronic properties of the novel dye type.