2H-Pyrano[3,2-c]chromene-2,5(6H)-diones: Synthesis, characterization, photophysical and redox studies for potential optoelectronic applications

Herein, we report the preparation of 2 H -pyrano[3,2-c]chromene-2,5(6 H )-diones 3a - x by reacting 4-hydroxycoumarins 1a-b with Baylis-Hillman adducts 2a-w having electron releasing or electron withdrawing groups on benzyl ring of the pyranochromene moiety and study of their photophysical properties. The study of optical and electrochemical properties of the prepared compounds reveals that the electron releasing and electron withdrawing groups has not much impact on ground and excited state electronic behavior on pyranochromene moiety. The density functional theory suggests the highest occupied molecular orbital and lowest unoccupied molecular orbitals spread on coumarin moiety of pyranochromene unit. Further, these compounds are thermally stable (up to 200 o C) and lead to blue or green emission that should facilitate the development of organic light emitting diodes (OLEDs).