Novel xanthene push-pull chromophores and luminophores: Synthesis and study of their spectral properties

Abstract

Spectral properties of five derivatives of 4-aminochromene containing formylated partially hydrogenated five or six-membered cycles, and two derivatives of 4-aminochromen-2-ylidene-malonaldehyde have been studied. The cyclic derivatives absorb light with the maxima around 430, nm and emit near 550 nm with a luminescence quantum yield of 0.056–0.135 in acetonitrile solution. The non-cyclized derivatives of 4-aminochromene with a malonaldehyde moiety possess emission in solid state in the red region with a moderate Stokes shift of 43 nm and 67 nm. Derivatives of 4-aminochromene containing formylated partially hydrogenated five or six-membered cycles were derivatized with active CH-acids to give seven Knoevenagel condensation products. Absorption spectra of these condensation products in acetonitrile solutions are red-shifted by 102–184 nm, while emission maxima are red-shifted by only 71–117 nm, as compared to the corresponding initial formyl derivatives. In addition, the condensation products have 1.5–1.9 times higher extinction coefficient (60,600–79,600 M−1cm−1), while fluorescence quantum yields decreased to (0.003–0.034).