1,1,4,4-Tetracyanobutadiene-Functionalized Anthracenes: Regioselectivity of Cycloadditions in the Synthesis of Small Near-IR Dyes

Org Lett. 2021 Mar 19;23(6):2007-2012. doi: 10.1021/acs.orglett.1c00136. Epub 2021 Feb 26.

Abstract

Two small 1,1,4,4-tetracyanobutadiene-functionalized chromophores were obtained by careful leverage of the regioselectivity of the cycloaddition reaction of tetracyanoethylene with anthracene-ynamide derivatives, inducing either a [2 + 2] or a [4 + 2] Diels-Alder process. DFT calculations unraveled the mechanism of the [2 + 2] cycloaddition-retroelectrocyclization reaction sequence with ynamides and elucidated the differing mechanisms in the two substrates. The synthesized dyes presented panchromatic absorption extending into the near-IR and far-red/near-IR photoluminescence in the solid state up to 1550 nm.