Tetracyanobutadiene functionalized ferrocenyl BODIPY dyes.

Tetracyanobutadiene (TCBD) derivatives of ferrocenyl BODIPYs 2a-2c were designed and synthesized by [2 + 2] cycloaddition-retroelectrocyclization reaction of tetracyanoethylene (TCNE) with meso alkynylated ferrocenyl BODIPYs. The TCBD substituted ferrocenyl BODIPYs were designed in such a way that the distance between the ferrocenyl unit and the TCBD remains constant, whereas the distance between the BODIPY and the TCBD unit varies. The TCBD and BODIPY units were connected directly through a single bond (in 2a), through a phenylacetylene linkage (in 2b) and through a vinyl linkage (in 2c). The photonic and electrochemical properties of ferrocenyl BODIPYs were strongly perturbed by the incorporation of TCBD. The TCBD derivatives 2a-2c show red shifted absorption compared to their precursors 1a-1c. The single crystal structures of TCBD functionalized ferrocenyl BODIPYs 2a and 2c reveal extensive intermolecular hydrogen bonding but lack π-π stacking interactions.