Synthesis and properties of cross-linkable twin derivatives of 2-phenylindole

• Cross-linkable glass-forming twin derivatives of 2-phenylindole were synthesized.
• The thermal cross-linking was demonstrated by DSC and ATR-FTIR.
• Glass transition temperatures are in the range from 44 to 120 °C.
• Hole-drift mobilities exceed 10−4 cm2/Vs.

Synthesis and optical, thermal, electrochemical as well as photophysical properties of a series of new cross-linkable twin derivatives of 2-phenylindole with the different linkages are reported and compared. The compounds form molecular glasses with the glass transition temperatures in the range from 44 °C to 120 °C. They absorb electromagnetic radiation in the range of 225–420 nm and emit in the range of 400–600 nm. Compounds with ethenyl-containing linkages were found to exhibit very large Stokes shifts ranging from 142 nm to 159 nm for the dilute solutions and from 155 to 181 for the solid samples. The ionization potentials of the synthesized compounds were found to be in the range from 5.16 eV to 5.79 eV. Cyclic voltammetry showed that the synthesized diindolylethenes are electrochemically stable up to 1 V. The hole-drift mobility in the layers of the compounds exceeded 10−4 cm2/Vs at high electric fields. The ability of thermally initiated polymerization in the solid state of the monomers was demonstrated by DSC and ATR-FTIR spectroscopy.

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