Thermal and optical properties of 4H-pyran-4-ylidene fragment and bis-styryl and triphenyl groups containing derivatives

Abstract

Small D-π-A type organic molecules with incorporated 4H-pyan-4-ylidene (pyranylidene) fragment in their structures show potential in organic photonics -such as materials for organic light emitting diode application studies and organic solid state lasers. Additional incorporation of bulky triphenyl-groups in their structures gives them the ability to form thin amorphous solid films from volatile non-polar organic solvents. Unfortunately, there is still no clear relation between compound organic structures and their thermal and optical properties. In order to investigate the above mentioned regularities we have synthesized a series of tripheyl-group containing derivates of 2,6-bis-styryl-4H-pyran-4-ylidene with different stryryl-substituents and investigated their physical properties. The thermal decomposition temperatures of the obtained glassy 4H-pyran-4-ylidene compounds are in range from 198 o to 312 o C and depend from electron acceptor and styryl-groups while their glass transition temperatures are in range from 104 o to 132 o C and are mostly influenced by the electron acceptor fragment. The light absorption of synthesized 4H-pyran-4-ylidene compounds in solutions of dichloromethane as well as in their solid state are in range from 400 nm to 550 nm. Their photoluminescence spectra in the solid state (from 600 nm to 800 nm) are red-shifted by approximately 50 nm comparing to their photoluminescence spectra in solutions of dichloromethane (from 550 nm to 750 nm) and mostly depends on the N,N-ditrityloxyethyl-aminostyryl-electron donor substituent, 4H-pyran-4-ylidene π-system and on the electron-acceptor group. Synthesized compounds could be used as potential materials for light amplification.