One-pot π-extension approach of iminoindoles-to-α-carbolines as blue-light emitters using the cooperative basic system

Abstract

A simple DABCO-catalyzed domino reaction between tosyliminoindoles and arylidene malononitriles using NaHCO₃ as a cheap, non-toxic cooperative base is reported. The transition-metal- and oxidant-free one-pot π-extension reaction creates two new C–C and CN bonds that deliver good to high yields of a series of blue-fluorescent 2-amino-α-carboline derivatives with good thermal stability. In addition, the solvatochromic studies indicate that the emission peaks and Stokes shift values are slightly higher in the case of polar solvents. Moreover, all the tested α-carbolines emitted blue light in the 413–471 nm range and showed moderate to good quantum yields (Ø_f ≤ 0.74) with typical Stokes shift values (ΔŪ ≤ 6469 cm⁻¹). Notably, electrochemical studies confirm that the prepared chromophores exhibit reversible oxidation potential waves and quasi-reversible waves.