π-Expanded Coumarins: One-Pot Photo Synthesis of 5<i>H</i>-Benzo[12,1]tetrapheno[7,6,5-<i>cde</i>]chromen-5-ones and Photophysical Properties

Abstract

The synthesis of a unique type of π-expanded coumarin derivatives, bearing six fused phenyl rings, was achieved via one-pot Suzuki reaction and visible light-driven electrocyclization. The large π-expanded 5H-benzo[12,1]tetrapheno[7,6,5-cde]chromen-5-ones were obtained in good to high yields from 1-bromo-2H-phenaleno[1,2,3-de]chromen-2-ones, and the intriguing optical properties were explored by altering the attached functional groups. 2-Arylaminosubstituted-5H-benzo[12,1]tetrapheno[7,6,5-cde]chromen-5-ones showed a large Stokes shift (4005 cm–1) or excellent fluorescence quantum yield (Φf = 0.75) along with significant bathochromic shift in tetrahydrofuran.

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